Agenda packet — Diamond Bar City Council, March 17, 2026 (part 4 of 5)

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

FIGURES

2. Building Type Standards
2-1 Key Building Type Elements. . . . . . . . . . . . . . . . . . . . . . . . . . 14 2-2 Maximum Footprint per Story Diagram. . . . . . . . . . . . . . . . . 15 2-3 Common Open Space Diagram. . . . . . . . . . . . . . . . . . . . . . . . 15 2-4 Duplex, Triplex, Fourplex Diagram. . . . . . . . . . . . . . . . . . . . 17 2-5 Duplex, Triplex, Fourplex Illustrative Photo. . . . . . . . . . . . . 18 2-6 Townhouse Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 2-7 Illustration of a Townhouse Stacked over a
Separate Flat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2-8 Townhouse Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . 20 2-9 Section of a Townhouse. . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2-10 Section of a Townhouse Wrapping the Podium
of Garage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 2-11 Section of a Townhouse on a Sloping Site. . . . . . . . . . . . . . 20 2-12 Section of a Townhouse Not Permitted. . . . . . . . . . . . . . . . 20 2-13 Flex/Loft Building Diagram. . . . . . . . . . . . . . . . . . . . . . . . . 21 2-14 Flex/Loft Building Illustrative Photo. . . . . . . . . . . . . . . . . . 22 2-15 Auto Court or Six/Eight Pack Diagram. . . . . . . . . . . . . . . . . 23 2-16 Auto Court or Six/Eight Packt Illustrative Photo. . . . . . . . . 24 2-17 Auto Court or Six/Eight Pack Illustrative Photo. . . . . . . . . 24 2-18 Walk-Up Flats Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2-19 Walk-Up Flats Illustrative Photo. . . . . . . . . . . . . . . . . . . . . 26 2-20 Carriage House Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . 27 2-21 Concept Rendering of Carriage House. . . . . . . . . . . . . . . . . 28 2-22 Carriage House Illustrative Photo. . . . . . . . . . . . . . . . . . . . 28 2-23 Small Mixed-Use Building Diagram. . . . . . . . . . . . . . . . . . . 29 2-24 Small Mixed-Use Building Diagram. . . . . . . . . . . . . . . . . . . 30 2-25 Small Mixed-Use Building Illustrative Photo. . . . . . . . . . . . 30 2-26 Courtyard Multifamily Building Diagram. . . . . . . . . . . . . . . 31 2-27 Courtyard Building Illustrative Photo. . . . . . . . . . . . . . . . . 32 2-28 Wrap Building Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 2-29 Wrap Building Illustrative Photo. . . . . . . . . . . . . . . . . . . . 34 2-30 Urban Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 2-31 Urban Block Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . 36 2-32 Urban Block Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . 36 2-33 Mixed-Use Big Box Diagram. . . . . . . . . . . . . . . . . . . . . . . . . 37 2-34 Mixed-Use Big Box Illustrative Photo. . . . . . . . . . . . . . . . . 38 2-35 Mixed-Use Big Box Illustrative Photo. . . . . . . . . . . . . . . . . 38

3. Building Articulation Standards
3-1 Multiple Variations of Same Style . . . . . . . . . . . . . . . . . . . . 42 v

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

FIGURES
3-2 Mixed-Use Building Articulated with Corner. . . . . . . . . . . . . 42 3-3 Horizontal Articulation Diagram . . . . . . . . . . . . . . . . . . . . . 43 3-4 Vertical Articulation Diagram. . . . . . . . . . . . . . . . . . . . . . . . 43 3-5 Architectural Projections Diagram . . . . . . . . . . . . . . . . . . . 43 3-6 Architectural Recessions Diagram. . . . . . . . . . . . . . . . . . . . 44 3-7 Façade Differentiation Diagram. . . . . . . . . . . . . . . . . . . . . . 44 3-8 Architectural Style Differentiation Diagram. . . . . . . . . . . . . 44 3-9 Base, Middle, and Top Articulation Diagram. . . . . . . . . . . . . 45 3-10 Illustrative Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 3-11 Entrances. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 3-12 Windows. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 3-13 Variety of Rooflines Illustrative Photo. . . . . . . . . . . . . . . . 47 3-14 Encroaching Habitable Space. . . . . . . . . . . . . . . . . . . . . . . 48 3-15 Projecting Canopies. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49 3-16 Encroachment and Projections Diagram. . . . . . . . . . . . . . . 49 3-17 Illustrative Photo of Shopfronts in Mixed-Use Buildings. . . 50 3-18 Minimum Frontage Glazing Diagram. . . . . . . . . . . . . . . . . . 50 3-19 Changes of Colors and Materials Illustrative Photo. . . . . . . 51

4. Frontage Types
4-1 Shopfronts in Mixed-Use Buildings Illustrative Photo. . . . . . 57 4-2 Shopfronts in Mixed-Use Buildings Conceptual Plan . . . . . . 57 4-3 Shopfronts in Mixed-Use Buildings Illustrative Section. . . . . 57 4-4 Raised Commercial Terrace Illustrative Photo . . . . . . . . . . . 58 4-5 Raised Commercial Terrace Conceptual Plan. . . . . . . . . . . . 58 4-6 Raised Commercial Terrace Illustrative Section. . . . . . . . . . 58 4-7 Stoop Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4-8 Stoop Conceptual Plan. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4-9 Stoop Illustrative Section . . . . . . . . . . . . . . . . . . . . . . . . . . 59 4-10 Dooryard Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . . 60 4-11 Dooryard Conceptual Plan . . . . . . . . . . . . . . . . . . . . . . . . . . 60 4-12 Dooryard Illustrative Section. . . . . . . . . . . . . . . . . . . . . . . 60 4-13 Front Porch Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . 61 4-14 Front Porch Conceptual Plan. . . . . . . . . . . . . . . . . . . . . . . . 61 4-15 Front Porch Illustrative Section . . . . . . . . . . . . . . . . . . . . . 61 4-16 Forecourt Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . 62 4-17 Forecourt Conceptual Plan. . . . . . . . . . . . . . . . . . . . . . . . . 62 4-18 Forecourt Illustrative Section. . . . . . . . . . . . . . . . . . . . . . . 62 4-19 Raised Residential Terrace Illustrative Photo. . . . . . . . . . . 63 4-20 Raised Residential Conceptual Plan. . . . . . . . . . . . . . . . . . 63 4-21 Raised Residential Terrace Illustrative Section. . . . . . . . . . 63 vi

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

FIGURES
4-22 Urban Frontage Illustrative Photo. . . . . . . . . . . . . . . . . . . . 64 4-23 Urban Frontage Conceptual Plan. . . . . . . . . . . . . . . . . . . . . 64 4-24 Urban Frontage Illustrative Section. . . . . . . . . . . . . . . . . . 64

5. Site and Open Space Standards
5-1 Illustrative Photo of Terrace Frontage. . . . . . . . . . . . . . . . . . 67 5-2 Illustrative Photo Showing Outdoor Seating Areas, Cafes and Restaurants in Mixed-Use Conditions. . . . . . . . . . . . . . . . . . . . . 68 5-3 Illustrative Photo Showing Street Furnishings in Mixed-Use Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68 5-4A Two Tiers of Planting. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 5-4B Three Tiers of Planting. . . . . . . . . . . . . . . . . . . . . . . . . . . 69 5-5 Common Open Space Illustrative Photo. . . . . . . . . . . . . . . . 70 5-6 Interior Courtyard Illustrative Photo. . . . . . . . . . . . . . . . . . 70 5-7 Hedge Screening Service Area. . . . . . . . . . . . . . . . . . . . . . . 71 5-8 Service and Auxiliary Equipment Illustrative Photo. . . . . . . 73

6. Architectural Styles
6-1 Main Street Commercial Illustrative Photo. . . . . . . . . . . . . . 77 6-2 Main Street Commercial Illustrative Photo. . . . . . . . . . . . . . 77 6-3 Rectangular Form Percentage Diagram. . . . . . . . . . . . . . . . . 78 6-4 Large Windows Ground Floor. . . . . . . . . . . . . . . . . . . . . . . . 78 6-5 Decorative Brick. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 6-6 Single Plane. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 6-7 Cornice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 6-8 Parapet and Cornice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78 6-9 Awnings at Commercial Frontage. . . . . . . . . . . . . . . . . . . . . 79 6-10 Canopy Frontage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 6-11 Roof with Detailed Parapet. . . . . . . . . . . . . . . . . . . . . . . . . 79 6-12 Main Street Commercial Elements Diagram
(Ground Floor Commercial). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 6-13 Main Street Commercial Elements Diagram
(Ground Floor Residential). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 6-14 Spanish Revival Illustrative Photo. . . . . . . . . . . . . . . . . . . . 83 6-15 Spanish Revival Illustrative Photo. . . . . . . . . . . . . . . . . . . . 83 6-16 Volumetric Composition Diagram. . . . . . . . . . . . . . . . . . . . 84 6-17 Painted Base with Recess. . . . . . . . . . . . . . . . . . . . . . . . . . 84 6-18 Single Plane Composition. . . . . . . . . . . . . . . . . . . . . . . . . . 84 6-19 Balcony Overextending Sidewalk. . . . . . . . . . . . . . . . . . . . . 84 6-20 Parapet with Flat Roof. . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6-21 Clay Tile with No Eave. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 6-22 Spanish Revival Elements Diagram. . . . . . . . . . . . . . . . . . . 86 vii

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 6-23 Craftsman Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . 87 6-24 Craftsman Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . 87 6-25 Masonry and Stone Base. . . . . . . . . . . . . . . . . . . . . . . . . . . 88 6-26 Gutter and Downspout. . . . . . . . . . . . . . . . . . . . . . . . . . . . 88 6-27 Paired Openings Composed Horizontally. . . . . . . . . . . . . . . 88 6-28 Painted Shingles Over Siding. . . . . . . . . . . . . . . . . . . . . . . 88 6-29 Space Betweem Columns and Piers. . . . . . . . . . . . . . . . . . . 88 6-30 Craftsman Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . 88 6-31 Craftsman Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . 89 6-32 Bracketing of a Roof Gable. . . . . . . . . . . . . . . . . . . . . . . . . 89 6-33 Craftsman Elements Diagram. . . . . . . . . . . . . . . . . . . . . . . 90 6-34 Art Deco Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . . 91 6-35 Art Deco Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . . 91 6-36 Art Deco Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . . 92 6-37 Ground Floor as Base. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 6-38 Art Deco Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . . 92 6-39 Art Deco Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . . 92 6-40 Extensions with Metal Panels. . . . . . . . . . . . . . . . . . . . . . . 92 6-41 Undulating Parapet. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92 6-42 Stepped-Back Volumes. . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 6-43 Art Deco Illustrative Photo. . . . . . . . . . . . . . . . . . . . . . . . . 93 6-44 Art Deco Elements Diagram (Ground Floor Commercial). . . 94 6-45 Art Deco Elements Diagram (Ground Floor Residential). . . 95 6-46 California Contemporary Illustrative Photo. . . . . . . . . . . . 97 6-47 California Contemporary Illustrative Photo. . . . . . . . . . . . 97 6-48 Example of a Base Articulated as Glass Panels. . . . . . . . . 98 6-49 Example of California Contemporary Townhouse. . . . . . . . 98 6-50 California Contemporary Illustrative Photo. . . . . . . . . . . . 98 6-51 Different Materials Identify Different Façade Planes. . . . . . 98 6-52 Roof Articulated with Projected Metal Overhang
Serving as a Cornice. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98 6-53 California Contemporary Illustrative Photo. . . . . . . . . . . . 98 6-54 California Contemporary Illustrative Photo. . . . . . . . . . . . 99 6-55 California Contemporary Elements Diagram
(Ground Floor Commercial). . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 6-56 California Contemporary Elements Diagram
(Ground Floor Residential). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

7. Glossary of Terms
7-1 Isometric View of a Podium. . . . . . . . . . . . . . . . . . . . . . . . . 109

FIGURES
viii

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development TABLES
TABLES

1. Introduction
1-1 ODS Consistency Criteria. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 1-2 Step by Step Selection of Applicable Standards. . . . . . . . . . . 8

2. Building Type Standards
2-1 Building Type Matrix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2-2 Height in Stories for Courtyard Multifamily Building. . . . . . 31 2-3 Height in Stories for Wrap Building. . . . . . . . . . . . . . . . . . . . 33 2-4 Height in Stories for Urban Block. . . . . . . . . . . . . . . . . . . . . 35 2-5 Height in Stories for Mixed-Use Big Box. . . . . . . . . . . . . . . . 37

3. Building Articulation Standards
3-1 Building Articulation Standards Matrix. . . . . . . . . . . . . . . . . 42

4. Frontage Types
4-1 Frontage Type Matrix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 ix

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Diamond Bar Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Objective Design Standards for Multifamily & Mixed-Use Development Page Left Intentionally Blank

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development INTRODUCTION 1

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 2 INTRODUCTION • PURPOSE AND INTENT

INTRODUCTION

1.1 Purpose and Intent
The Objective Design Standards (ODS) that follow are applicable to proposals for multifamily housing or mixeduse development in the City of Diamond Bar. They are not applicable to projects without multifamily housing.

Their purpose is to set the minimum design standards required to assure that new development contributes to a “sense of place.”
All projects will be evaluated and based on their adherence to the ODS through a Development Review process that includes a mandatory checklist of applicable ODS.

The images in this document are for Illustrative purposes, only provided to illustrate intent.

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3 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development INTRODUCTION • GOALS

1.2 Goals
The Goals of these ODS are as follows:

Goal 1: Comply with state mandates to implement new Objective Design Standards for eligible multifamily housing and mixed-use development projects.

Goal 2: Ensure that appropriate Objective Design Standards are in place for housing development projects eligible for streamlined ministerial review pursuant to California Government Code Section 65913.4 and other State laws.

Goal 3: Ensure building placement and Frontage along existing or proposed streets reflects the intended character.

Goal 4: Establish architectural standards for larger buildings to mitigate overall mass and ensure visual interest from all public vantage points.

Goal 5: Create human-scaled development that contributes to pedestrian-oriented streets and boulevards in mixed-use zoning districts.

Goal 6: Provide design details and illustrations that are prescriptive and objective.

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 4 INTRODUCTION • DESIGN PRINCIPLES

1.3 Design Principles
Principle 1: Maintain—and in some cases, elevate—architectural variety, integrity, and quality.

Principle 2: Ensure that streets and spaces with high volumes of pedestrian traffic are comfortable, protected from the sun, and visually and physically engaging at the ground level.

Principle 3: Create architectural variation along a Block Front through diversity of massing, articulation, and architectural detailing.

Principle 4: Animate building edges on the ground floor to create an inviting Public Realm and pedestrian friendly environment and to support multi-modal development and mobility.

Principle 5: Orient building Façades to frame the streets and other Public Spaces and to take advantage of natural features such as sunset, sunrise, mountain views and the like.

Principle 6: Provide graceful transitions between larger-scale format of multifamily structures and adjacent smaller scale single-family housing.

Principle 7: Provide standards such that new buildings can sit comfortably adjacent to existing buildings of varied styles.

Principle 8: Provide off-street parking in surface lots or garages at the rear of buildings so that parking does not dominate the built environment.

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5 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

1.4 Applicability
Title 22 of the Diamond Bar City Code (DBCC) (“Development Code”) establishes a Development Review process for new multifamily housing when a proposed project is determined to be consistent with the City’s General Plan, applicable Specific Plan or Zoning District regulations, and conforms with the City’s Objective Design Standards.

These Objective Design Standards will apply to construction projects located anywhere in the City involving the development or substantial improvement of any of the following:

1. Multifamily residential projects, including duplexes, townhouses, or multifamily dwellings.

2.Mixed-use projects featuring a combination of multifamily residential and other uses.

1.4.1 Substantial Improvement
Objective Design Standards apply to any substantial improvement to existing multifamily or mixed-use development where any extension, repair, reconstruction or other improvement of a property, the cost of which equals or exceeds fifty (50) percent of the fair market value or assessed value of a property either before the improvement started or, if the property has been damaged, before the damage occurred. Any and all building additions to buildings for which these standards are applicable shall match the style and details of the main structure.

1.4.2 Non-Applicability
Single-family homes and projects with no residential component are not subject to these standards.

INTRODUCTION • APPLICABILITY

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 6 INTRODUCTION • CHECKLIST FOR STREAMLINED REVIEW
Table 1-1: ODS Consistency Criteria
• Orient building Façades to frame
streets/Public Spaces to promote a
pedestrian-friendly environment
• Buildings are located at the front of
the lot and face the street
• Incorporate building entrances and
windows along the Façade
Human-Scaled
Environment
(Principle 4 and
Goal 5; see sections

2.1-2.12)
Appropriate Use of
Building Types (Goal 4;
see section 3.1-3.13)
Architectural Style
(Principle 1; see
Chapter 7)
Building Articulation
and Massing
(Principles 3 and 4;
see sections 4.1, 4.2
and 4.4)
Appropriate Transitions
with Adjacent Buildings
(Principles 6 and 7; see
Section 4.3)
Appropriate Frontage
Types (Goal 3 and 4;

5.1-5.10)
Common and Private
Open Space (Principles
2, 5 and 8; Section 6.5)
• Building(s) adheres to the typespecific standards/guidelines of the following: maximum Façade Width,
pedestrian access, parking, outdoor
space, landscape, Frontage Types
and building massing
• Design features and detailing
are consistent with the selected
Architectural Style
•Create visual interest and break
up the overall massing of larger
buildings
•Well-articulated and detailed
Façades
• Appropriate transitions are
provided between building(s)
and adjacent single-family
neighborhoods
• Building Frontages address the land
use context and street environment
appropriately
• Building Frontages do not address land
use and street context appropriately
• Scale and massing of development
does not respond to existing context or
architectural character
• Façades are long, blank walls with little
detailing
• Little to no horizontal and vertical
articulation
• Provides Common Open Space that
is an amenity for residents
• Private Open Space with a patio
area or balconies for residents living
above the ground floor
• Common Open Space is not integrated
into the overall design of the project
• Balconies are not incorporated into
residential units on upper floors
• Buildings are separated from the street
by parking areas
• Lack of windows/entrances along the
Façade to provide a conducive walking
environment
• Building(s) do not adhere to the typespecific standards and do not create a human-scaled and pedestrian-oriented
environment
• Design features and detailing are not
representative of the Architectural Style
selected
Design Principles Consistent Not Consistent

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7 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development INTRODUCTION • HOW TO USE THIS DOCUMENT

1.5 How to Use This Document
This document provides Objective Design Standards (ODS) to ensure consistent, transparent, and measurable review of development projects in accordance with California State law. These standards are intended to streamline project approvals by providing clear, verifiable criteria for design that do not require subjective interpretation. They assume compliance with the underlying zoning except as noted herein.

To effectively use this document:

1. Understand the Structure of the Document
The standards are organized by design components—such as layout, massing, Façade Width, entrance locations, open space, and landscaping—tailored to each menu of options. Each section includes:
a. Purpose Statement: Explains the design intent.
b. Objective Standards: Measurable and enforceable requirements. c. Illustrations (if applicable): Visual examples to clarify standards. d. Capitalized words or phrases are defined in the Glossary. See Chapter 7.

2. Use these Standards During Project Design
Project teams should reference these Standards early in the design process. Each applicable standard must be met as written, without need for discretionary interpretation.

3. Select Applicable Building and Frontage Types as well Building Articulation and Massing Standards and Architectural Styles. (See Table 1-2: Step by Step Selection of Applicable Standards) Before using the detailed design standards, applicants must select from a menu of applicable Building Types, Building Articulation and Massing Standards, Frontage Types, and Architectural Styles for their project site. Choosing from the appropriate types ensures that the project is matched with the correct set of standards in the guide. In many cases, zoning regulations, site context, overlay districts or Specific Plans may limit or guide the allowable types. Applicants shall also comply with the Site and Open Space Standards.

The selection of standards is described in Table 1-2 as a series of steps. This step-by-step method is offered for clarity only as it is understood that architectural design is not a linear process.

4. Prepare Submittal Materials Accordingly
Clearly document how each applicable standard is met using diagrams, plans, elevations, and written justifications. This will speed up the review process and reduce requests for clarification.

5. City Review Process
City staff will review your project strictly against the objective standards. If all standards are met, the project will be referred to the applicable review authority with a recommendation for approval.

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 8 Step 1 Determine Applicable
Building Type Chapter 2
Refers to the general massing and configuration of the
structure (e.g., Townhouse, courtyard apartment, Wrap
building, Podium building). Each type has its own dimensional and design parameters.

Step 2
Determine Applicable
Building Articulation
Standards
Chapter 3
Refers to the requirements for building articulation and massing. These requirements ensure that buildings maintain appropriate scale, provide visual variety, and contribute positively to the character of streets and neighborhoods — without relying on subjective design opinions.

Step 3
Determine Applicable
Frontage Type
Standards
Chapter 4
Refers to how the building addresses the Public Realm or street (e.g., Shopfront, porch, Stoop, Forecourt). The selected Frontage dictates the rules for entries, transparency, Setbacks, and other elements at the street edge.

Step 4
Check compliance
with Site and Open
Space Standards
Chapter 5
Are applicable to all Building Types and regulate functional aspects of building form such as materials, lighting, service, parking and auxiliary spaces, landscape and outdoor space design. This section is intended to ensure that development is consistent with the goal of creating a human-scale mixed- use environment in which each individual building furthers the overall vision.

Step 5
Determine Applicable
Architectural Style
Standards
Chapter 6
Applicants must choose an Architectural Style from the set of styles allowed. Architectural Style provides a consistent visual language for detailing, proportions, and materials—and when defined objectively, it ensures predictable, high-quality outcomes without relying on subjective design review.

INTRODUCTION • HOW TO USE THIS DOCUMENT
Table 1-2: Step by Step Selection of Applicable Standards

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9 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

1.6 Relationship with General Plan and Development Code This document is incorporated by reference into the Development Code. If any standards, terms or other provisions from these ODS are found to be in conflict with objective standards set forth in other provisions of the Development Code and not specifically called out as superseding those standards, the standards set forth in the Development Code shall govern.

A. General Plan
The General Plan contains objective standards related to development Density for all land uses in the City. The Objective Design Standards in this document are consistent with the General Plan and dictate the bulk, mass, and design of buildings in a more fine-grained way than the General Plan.

B. Zoning
The Development Code located in Title 22 of the City Code contain standards that define Floor Area Ratio (FAR) and land use will continue to dictate basic development standards, and these ODS will apply as part of the Development Code, providing refinement in terms of site and building design.

C. Other City Code Sections
The City also maintains and enforces standards related to stormwater drainage, Roadway and traffic requirements, hillside development, and standards for work within the public right-of-way to install sidewalks, street trees, and lighting. All construction is subject to Title 15 of the City Code which incorporates the California Building Code with local amendments.

These standards will continue to apply unless specifically superseded in this document.

INTRODUCTION • RELATIONSHIP WITH GENERAL PLAN AND DEVELOPMENT CODE

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 10 Page Left Intentionally Blank

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

BUILDING TYPE
STANDARDS 2

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 12

BUILDING TYPE

STANDARDS

2.1 Introduction
To support a variety of household types and foster a rich, diverse built environment, these Objective Design Standards promote a broad range of Building Types. Options include Townhouses, flex/lofts, walkups, Courtyard Buildings, urban Block structures, and wrap buildings. Additional standards address mixed-use configurations compatible with these residential types.

Once a specific Building Type is selected, the development must conform to its associated standards, including maximum Façade Width, pedestrian access, parking, common open space, landscaping, Frontage Types, and overall massing.

These standards are designed to encourage architectural diversity and ensure all buildings contribute to an active Public Realm while providing private outdoor amenities—such as gardens, courtyards, and porches— where appropriate.

While there is flexibility in selecting Building Types within each Block or zoning district, only certain types may be appropriate depending on adjacent uses and other constraints. In the absence of a specific plan, applicants in mixed-use zones must submit a site plan that defines Block layouts and identifies at least two Building Types per Block. This requirement does not apply to developments within multifamily zones.

BUILDING TYPE STANDARDS • INTRODUCTION

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13 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

2.2 Explanation of Standards
This chapter provides standards for the following
eleven Building Types.

For each Building Type, the standards described below
are provided. See Table 2-1 for a summary of Building
Types.

These standards are intended to avoid monotonous
building designs in favor of more varied designs with
reduced bulk at the upper stories. The Building Type
standards cover the following:

A. Intent Statement
This statement defines and describes the
development intent and typical characteristics for
the respective Building Type.

B. Applicability
This statement explains whether the type is
permitted solely in mixed-use zones, or in both
mixed-use and multifamily zones.

C. Façade Width
Façade Width standards regulate the maximum
width of a building. However, this dimension may
be exceeded if one of the following strategies is
employed:

Strategy 1

1. The building is designed to appear as two or
more buildings, with distinct entries for each
Apparent Building, and such that the space
between each Apparent Building is at least 20
feet in width. These buildings may be connected
above the ground floor via corridor “bridges”
that are set back a minimum of 25 feet from the
Façade Plane.

Strategy 2

2. Utilize any four of the following techniques:
a.Provide a material change for the entire Height
of the massing element.
b.Provide a change in the overall type, size,
spacing, or proportion of windows or
Fenestration system or change in sill Heights
and head conditions.
c. Provide a change in Façade Composition
including roof Heights, and roof types. For
example, placing a symmetrical Façade next to a
Façade with a repetitive bay system that is not
symmetrical would comply with this standard.
d.Provide a change in building Height by at least
10 feet or one-Story.
e.Provide separate and additional primary entries
from the street.
f. Provide a change in Architectural Style.

D. Building Height & Massing
Height standards regulate the maximum building
Height. Building Height shall be defined pursuant to
the Development Code.

Some Building Types require horizontal or vertical
Plane Breaks or both (see also Figure 2-1).

Horizontal Plane Breaks shall not alleviate
the minimum Building Frontage Occupancy
requirements. Building Façades facing Build-to
Lines shall provide Plane Breaks in a manner
such that the overall Building Frontage meets
the minimum Building Frontage Occupancy
requirements. Plane Breaks are only required at
street-facing Façades.

Furthermore, a maximum allowed Footprint per
Story is presented for certain Building Types. The
maximum allowable Footprint per Story limits
the percentage of occupiable space per building
Story in relationship to the building’s groundfloor Footprint. For example, a four-Story building that limits the maximum allowable Footprint of
the fourth Story to 60 percent may satisfy this
requirement by providing stepbacks, decks, patios,
building articulation, or similar massing strategies
that ensure that the fourth Story occupies no more
than 60 percent of the building. Balconies shall
count toward the maximum allowable Footprint
unless there is at least 18 feet of vertical airspace
between each balcony deck and floor unit.

BUILDING TYPE STANDARDS • EXPLANATION OF STANDARDS

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 14 BUILDING TYPE STANDARDS • EXPLANATION OF STANDARDS
A
Figure 2-1 - Key Building Type Elements
Plane Break:

The area of the building where the plane of the Façade
varies in depth, represents a Plane Break.
is a Horizontal Plane Break.
is a vertical Plane Break.

Common Open Space:

Each Building Type requires the Lot Area to be
occupied by a certain percentage of green space area,
which can be accommodated in a variety of ways, for
instance through gardens, yards, patios, courtyards,
etc. as described on each Building Type page.

Maximum Footprint per Story:

The floor area of upper stories shall be less than the
area of the building Footprint at grade as indicated by the maximum allowed Footprint per Story charts on
each Building Type page.

Frontage Type:

Each building has certain Façade conditions that
are called Frontage Types. Each Frontage interacts
differently with the street and therefore is appropriate for different areas and Building Types.

A
B
B
Maximum Upper Level Building Frontage Occupancy:

Some Building Types have limitations on the
percentage of the building front that can be occupied
above 45 feet in Height. A standard may limit upper
levels to 80% of a Frontage, requiring either a break
in Frontage or a Setback of the Building Face by a
minimum of 8 feet.

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15 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING TYPE STANDARDS • EXPLANATION OF STANDARDS
E. Maximum Upper-Level Frontage
Occupancy
Certain Building Types have limitations on the
percentage of the Building Frontage that can be
occupied above 45 feet in Height, where such
heights are permissible. These standards are
included in order to provide more variety and
visual interest at the upper levels. The upper-level
Frontage Occupancy is based on the ground-floor.

F. Frontage Types
This standard lists which Frontage Types are
permitted for each Building Type.

G. Pedestrian Access & Entries
This standard regulates the location and
orientation of building entries.

H. Parking
Building Type parking standards provide parking
design regulations that are specific to each Building
Type.

I. Common Open Space

1. Each Building Type requires a specific amount
of outdoor space to be designated on site.

Ground floor Setbacks less than 15 feet in depth
shall not count towards fulfilling the outdoor
space requirement.

2. Required outdoor space may either be private,
only accessible to the occupants, or open to the
general public. Outdoor space may be located
at grade, atop a Podium or at the rooftop
unless the location is restricted by the selected
Building Type. Regardless of location, the design
of outdoor space shall maximize solar access.

3. Required outdoor space can be shared between
adjacent Building Types, as long as the
cumulative minimum requirements for each
type are satisfied.

J. Landscape
The landscape standards regulate the design of
common open space including the amount of
common open space that is required to be planted
with vegetation.

Site
Ground Floor
Footprint
Figure 2-2 - Maximum Footprint per Story Diagram
The maximum Footprint per Story is computed based on the building’s ground floor Footprint, not the overall site area.

Figure 2-3 - Common Open Space Diagram
Adjacent buildings may combine the required outdoor spaces into one shared space provided the cumulative minimum
requirements for each building is met.

Building 1 Building 2
Common Open Space

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 16 BUILDING TYPE STANDARDS • ALLOWABLE BUILDING TYPES
Table 2-1: Building Type Matrix
Building Type Typical Height Frontage Width
Common Uses
(Land use shall
conform with
Zoning Ordinance)
1 Duplex/Triplex/
Fourplex 1-3 Stories 50-90 feet Small Multifamily
2 Townhouse
(Attached Row) 2-4 Stories
18-26 ft/unit
(Maximum string
length is 200 feet)
Residential, fee simple ownership
3 Flex/Loft or
Shopfront, LiveWork2-4 Stories 18-26 ft/unit Small business + Residential 4 Auto Court or Six/
Eight Pack 2-4 Stories Varies Rental or Condo Multifamily 5 Walk-Up Flats 2-3 Stories 75-150 feet Rental or Condo Multifamily 6 Carriage House 2-3 Stories 50-120 feet
Used to line the rear of edge parking
lots of apartment communities where
those parking lots front streets or
alleys
7 Small Mixed-Use
Building 2-3 Stories 50-100 feet
Along sites fronting commercial
corridors where ground floor retail is
desired
8 Courtyard
Multifamily 3-5 Stories 50-75 feet Rental or Condo – Multi-family with Ancillary Mixed-Use 9 Wrap Building 4-6 Stories 150-250 feet
Residential wrapped around structured parking, often with ground floor retail
10 Urban Block 3-5 Stories
(Over Podium) 100-200+ feet Mixed-use, residential above retail 11 Mixed-Use Big Box 55-75 feet Up to 300 feet Residential over a large format retail store

2.3 Allowable Building Types
Allowable Building Types are as described in this section, 2.3 and summarized in Table 2-1.

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17 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING TYPE STANDARDS • DUPLEX, TRIPLEX, FOURPLEX

2.3.1 Duplex, Triplex, Fourplex
A. Intent Statement
A structure that consists of two to four primary
dwelling units.

B. Applicability
All multifamily and mixed-use zones.

C. Façade Width
Maximum Façade Width is 90 feet.

D. Building Height & Massing

1. Maximum Height is Three stories.

2. The second and third stories may occupy the
full ground floor Footprint area.

3. Attic space may be occupied and not count
as a Story. Occupiable attic space shall not
exceed fifty percent (50%) of the ground floor
Footprint area.

4. Building Faces abutting side streets or yards
shall provide at least 1 Horizontal Plane Break of
at least three feet, and one vertical Plane Break
of at least two feet.

E. Maximum Upper-Level Frontage
Occupancy
Not applicable.

F. Frontage Types

1. Permitted Frontage Types for street facing
units: Front Porch and Stoop. (See Sections 4.5
and 4.7)

2. No specified Frontage types are required for
non-street or paseo facing units.

G. Pedestrian Access & Entries

1. At least one (1) Primary Entrance to a dwelling
unit shall be accessed directly from and face the
street or paseo.

2. Where an alley is not present, parking and
services shall be accessed by a Driveway,
consistent with DBCC Section 22.30.080.

3. On a corner lot without access to an alley,
parking and services shall be accessed from the
side street, by a Driveway consistent with DBCC
Section 22.30.080.

4. Buildings that do not front a street must front
a courtyard or paseo and have at least one
Primary Entrance to a dwelling unit accessed
directly from the courtyard.

5. Multiple front doors shall not be placed within
10 feet of one another unless there is a porchat least six feet in depth in front of them.

H. Parking

1. Parking may be accommodated at grade on the
lot, in a common surface lot, in a carport, in a
garage on the lot, or in a common garage.

2. Tandem spaces are permitted.

3. Parking shall be at the rear of the lot or in the
middle of the Block, separated and screened
from view from the street.

4. Where parking is integral with the building,
garage doors shall not face the primary street
but may face a secondary street if the building
is on a corner lot.

Figure 2-4 - Duplex, Triplex, Fourplex Diagram
MAX 90’

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 18 Figure 2-5 - Duplex, Triplex, Fourplex Illustrative Photo BUILDING TYPE STANDARDS • DUPLEX , TRIPLEX, FOURPLEX

5. Guest parking spaces may be accommodated
with on-street spaces along streets and
alleyways adjacent to the building. All onstreet parking shall be subject to all applicable regulations, including the Development Code
and California Vehicle Code.

6. Where parking abuts a side street, it shall be
screened from view pursuant to DBCC Section

22.30.070(8).

I. Common Open Space

1. At least 15 percent of the Lot Area shall be
provided as common open space.

2. Common Open space types that count toward
the satisfaction of the required amount of
outdoor space are porches, patios, verandas,
balconies, yards, and decks.

3. Landscaped outdoor space shall be planted with
native or adapted landscape.

4. Where courtyards are used to satisfy open
space requirements, the courtyard shall be
enclosed on at three sides by building walls
or shall include at least one building or unit
entrance on each side of the courtyard.

5. Common Open Spaces
a. Each residential unit shall be provided a
direct, pedestrian path of travel to common
open spaces.
b. Amenities that may be counted toward open
space requirements: tot lot/play structure,
community garden, picnic tables and BBQ
area, swimming pool, indoor recreation
facility, sport courts, and natural open
space.

J. Landscape
All outdoor space shall be landscaped or
Hardscaped.

K. Additional Standards

1. Where a project includes no more than two
buildings, the buildings may be identical in
design

2. Where more than two buildings are on a site,
no more than two may be designed as identical
and must differ by meeting at least four of the
criteria identified in Section 3.2.

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19 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING TYPE STANDARDS • TOWNHOUSE
Primary Street
Side Street

2.3.2 Townhouse
A. Intent Statement
A structure that consists of at least three
primary residences with common walls, side by
side along the Building Frontage. The structure
has parking behind the building, either integrated
with the building or in surface spaces accessed
from an alley. Alternatively, parking may be part
of a structure shared with other Building Types.

Townhouses may also wrap the base of a Podium.
(See Figure 2-10).

B. Applicability
All multifamily and mixed-use zones.

C. Façade Width

1. Maximum of 26 feet for each Townhouse unit,
except that the Façade Width of a Townhouse
on Block corners may be up to 45 feet per
Frontage.

2. The maximum length of a string of attached
Townhouses is 200’.

D. Building Height & Massing

1. See DBCC Section 22.08.040 for Height limits
in the multifamily zones. In mixed-use zones,
the maximum Height shall be 45 feet. See DBCC
Section 22.16.060 for Height measurement and
Height limit exceptions. Notwithstanding the
foregoing, where topography requires a Stoop
to access the ground floor, the Height shall
be measured from the top of the Stoop. (See
Section 4.5)

2. Façade Strings shall have at least one
Encroachment per 100 linear feet, such as a
porch, balcony, or Plane Break. The combined
length of Plane Breaks shall occupy at least 10
percent of the Façade length.

3. Building Faces abutting side streets or yards
shall provide at least one Horizontal Plane
Break of at least three feet, and one vertical
Plane Break of at least two feet.

4. In a three-Story building, a two-Story
Townhouse may be stacked over a separate
ground- floor unit. (See Figure 2-7)
E. Maximum Upper-Level Frontage
Occupancy
Not applicable.

F. Frontage Types
Permitted Frontage Types: Stoop, Dooryard (See
Sections 4.5 and 4.6).

G. Pedestrian Access & Entries
The Primary Entrance shall be accessible directly
from the street, through the Frontage or from the
fronting paseo.

H. Parking

1. Garages shall accommodate no more than two
cars and shall be integrated into the back of the
Townhouse, behind a habitable room.

2. Parking may be accommodated on surface lots,
behind the structure.

3. Podium parking is permitted, in which case a
unit may also be accessed from the parking
area or internal building corridor, and no
individual garage parking is required.

MAX 200’

FRONTING PASEO
35’-45’
MAX
Figure 2-6 - Townhouse Diagram

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 20 BUILDING TYPE STANDARDS • TOWNHOUSE
Figure 2-8 - Townhouse Illustrative Photo
Figure 2-7 -Illustration of a Townhouse Stacked over a
Separate Flat
Figure 2-10 - Section of a Townhouse Wrapping the Podium of Garage
Figure 2-9 - Section of a Townhouse
Figure 2-11 - Section of a Townhouse on a Sloping Site
Figure 2-12 - Section of a Townhouse Not Permitted

4. Parking in garages or perpendicular spaces
accessed from the front of the building are not
permitted.

I. Common Open Space

1. Amount required. At least 10 percent of the Lot
Area shall be provided as common open space.

2. Types. Permitted common open space types
that count toward the required amount of open
space are: elevated Terraces, patios, verandas,
balconies, yards, decks, and roof gardens

3. Design. The common open space area must
be open to the sky, except for any allowable
Encroachments, as permitted in Section 3.8,
and any Shade Structures within the space.

J. Landscape
All common open space shall be landscaped or
Hardscaped.

Habitable Room
Permitted Outdoor
Space
2-STORY 2-STORY
Garage
Garage
Townhouse Garage
Townhouse
Front
Front
Front

ENTRANCE TO
1-STORY FLAT
2-STORY Townhouse ENTRANCES
Front
1-STORY
FLAT

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21 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING TYPE STANDARDS • FLEX/LOFT BUILDING

2.3.3 Flex/Loft Building
A. Intent Statement
Flex/Loft Building is a structure in which each
unit functions as an integrated residence and
work space. These units are typically arranged
side by side along the Principal Frontage and are
designed or structurally modified to accommodate
joint residential and work occupancy. Flex/Loft
Buildings may also wrap the base of a Podium
structure.

B. Applicability
Mixed-use zones only.

C. Façade Width

1. A maximum of 30 feet for each flex/loft unit.

Except that the Façade Width of a Flex/Loft
Building on Block corners may be up to 45 feet
Frontage.

2. The maximum number of attached flex/loft
units is a 10-Façade String.

D. Building Height & Massing

1. Maximum Height shall be 45 feet.

2. Façade Strings shall have at least one
Encroachment per 100 linear feet, such as a
porch, balcony, or Plane Break. The combined
length of Plane Breaks shall occupy at least 15
percent of the Façade length.

3. Building Faces abutting side streets or yards
shall provide at least one Horizontal Plane
Break of at least three feet, and one vertical
Plane Break of at least two feet.

E. Maximum Upper-Level Frontage
Occupancy
Not applicable.

F. Frontage Types
Permitted Frontage Types: Shopfront, Commercial
and Residential Terrace, Dooryard (See Sections

4.3, 4.4, 4.6, 4.9).

G. Pedestrian Access & Entries
The Primary Entrance shall be accessible directly
from the street, through the Frontage, except
that primary residential entries may be accessed
through work space, through a fronting paseo
between units, or from the rear.

H. Parking

1. Individual garage parking may be integrated
into the back of the Flex/Loft Building but must
be behind a habitable room.

2. Parking may be on a surface lot behind the
structure.

MAX 10 UNITS
45’
MAX
Figure 2-13 - Flex/Loft Building Diagram

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 22 Figure 2-14 - Flex/Loft Building Illustrative Photo
BUILDING TYPE STANDARDS • FLEX/LOFT BUILDING
I. Common Open Space

1. Amount required. At least 15 percent of the Lot
Area shall be provided as common open space.

2. Types. Permitted common open space types
that count toward the required amount of open
space are: elevated Terraces, patios, verandas,
balconies, yards, decks, and roof gardens.

3. Design. The common open space area must
be open to the sky, except for any allowable
Encroachments, as permitted in Section 3.8,
and any Shade Structures within the space.

J. Landscape
All common open space shall be landscaped or
Hardscaped.

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23 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING TYPE STANDARDS • AUTO COURT OR SIX/EIGHT PACK

2.3.4 Auto Court or Six/Eight Pack
A. Intent Statement
A building or an arrangement of buildings that
contains between six and eight residential units
that share a common Driveway. The primary
pedestrian access shall be located from a Street,
Open Space or Common Walkway. In mixed-use
zones, the ground floor of each unit may include
ground-floor retail or commercial uses. Auto
Courts may be paired, creating common walkways
or courtyards. However, this pairing is permitted
no more than three times in a row. Services,
utilities and trash container areas shall be located
on the Common Driveway.

B. Applicability
All multifamily and mixed-use zones.

C. Façade Width
The width of the Façade may vary.

D. Building Height & Massing

1. Maximum Height: As permitted in the applicable
zoning district, but no taller than four stories.

2. The upper stories may occupy the full ground
floor Footprint area.

3. Maximum building dimension along primary
street Frontages: 50 feet. Along side streets,
Façades longer than 50 feet in length shall
provide at least one Vertical Plane Break of at
least two feet.

E. Maximum Upper-Level Frontage
Occupancy
Not Applicable.

F. Frontage Types
Permitted Frontages: Stoop, Dooryard, Front Porch
and along the street only Shopfront and Raised
Commercial Terrace are also permitted. (See
Sections 4.3, 4.4, 4.5, 4.6, 4.7)
G. Pedestrian Access & Entries

1. Primary access to ground-floor spaces shall be
directly from the street or common walkway or
open space.

2. The Common Walkway shall connect to a Street
or Open Space, not to an Alley or Driveway, on
at least one end.

3. Primary pedestrian access is not permitted
from an Alley.

H. Parking

1. Parking and services shall be accessed through
a Driveway or an alley.

2. Garages may be integral with or detached from
the primary dwelling and they shall face the
Common Driveway.

Figure 2-15 - Auto Court or Six/Eight Pack Diagram
Common
Driveway
Street
Common
Walkway or
Paseo

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 24 BUILDING TYPE STANDARDS • AUTO COURT OR SIX/EIGHT PACK
I. Common Open Space
Not required.

However, where Auto Courts are paired to create a
common walkway the following Standards apply:

1. The front Setback along the Common Walkway
shall be at least 10 ft from the center-line of the
sidewalk resulting in a Building Face to Building
Face width of at least 20 feet.

2. The Common Walkway shall measure at least
five feet in width.

3. Unenclosed porches may encroach into the
Setback by up to seven feet provided that they
are no higher than four feet above grade.

4. Fences, walls or hedges are allowed along the
Common Walkway at fronts of homes, provided
they are Setback from the walkway by at least
two feet and are no taller than three feet from
the Grade of the Common Walkway.

5. Bay windows may encroach into the Setback by
up to two feet.

J. Landscape

1. The Common Walkway path shall be a minimum
of five feet in width.

2. All common open space shall be landscaped or
Hardscaped.

3. Fences, walls or hedges are allowed along the
Common Walkway at fronts of homes, provided
they are Setback from the walkway by at least
two feet and are no taller than 42 inches from
the Grade of the Common Walkway.

Figure 2-16 - Autocourt or Six/Eight Pack Illustrative
Photo
Figure 2-17- Autocourt or Six/Eight Pack Illustrative
Photo

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25 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING TYPE STANDARDS • WALK-UP FLATS

2.3.5 Walk-Up Flats
A. Intent Statement
A structure that consists of four to 12 dwelling
units accessed from one common staircase
accommodating up to four units per floor. The
building may contain residential or commercial
uses on the ground floor with residential uses
above. The Walk-up may be repeated along a
primary Frontage or within a Block subject to the
massing requirements of the Building Type.

B. Applicability
All multifamily and mixed-use zones.

C. Façade Width
Maximum Façade Width is 150 feet. However up to
three Walk-Up Buildings may be adjoined provided
that each building appears as a separate structure
from the adjacent one. Methods for achieving this
are included in Section 3.2.

D. Building Height & Massing

1. Maximum Height: Three stories.

2. Upper stories may occupy the full ground floor
Footprint area.

3. Attic space may be occupied and not count as
a Story. Occupiable attic space shall not exceed
50% of the ground floor Footprint area.

4. Building Faces abutting side streets or yards
shall provide at least one Horizontal Plane
Break of at least three feet, and one vertical
Plane Break of at least two feet.

5. Where the building is repeated, each building
shall front the primary street or the perimeter
of a Block.

6. Repeated buildings shall be provided with
different materials, colors and/or Architectural
Styles.

7. No more than three walk-up units may be
attached in a row per floor. Of these, no more
than two adjacent units may have identical
Façades.

8. A fourth walk-up unit may be added at the end
of the row if it is designed to turn the corner.

This pattern may be repeated on each floor.

9. Buildings may be grouped to form a courtyard.

E. Maximum Upper-Level Frontage
Occupancy
Not applicable.

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 26 BUILDING TYPE STANDARDS • WALK-UP FLATS
Figure 2-19 - Walk-Up Flats Illustrative Photo
G. Pedestrian Access & Entries

1. All units shall be accessed from a common stair
lobby. However, ground floor units may also be
accessed from the primary street.

2. Primary pedestrian access to the common
stair lobby shall be provided from the street,
a fronting mews or a common courtyard. A
second access may be provided from the rear.

3. Primary pedestrian access is not permitted
from an alley.

H. Parking

1. Parking shall be accommodated at grade and/
or tuck-under at the rear of the building, in a
common surface lot in the middle of the Block,
or against an alley. Connectivity to adjacent
parking lots where present shall be provided.

2. Surface lots that face an alley shall be screened
from view from the side street by a garden wall,
fence or hedge.

3. Services, utilities and trash container areas shall
be located off the alley, where present.

4. Parking and services shall be accessed from an
alley where present.

5. Where an alley is not present, parking and
services shall be accessed by a Driveway,
consistent with DBCC Section 22.30.080
(subject to approval by the Fire Department) or
by adjacent parking areas.

6. On a corner lot without access to an alley,
parking and services shall be accessed from the
side street by a Driveway consistent with DBCC
Section 22.30.080, unless a greater width is
required by the Fire Department.

I. Common Open Space

1. Amount required. At least 15 percent of the Lot
Area shall be provided as common open space.

2. Types. Permitted common open space types
that count toward the satisfaction of the
required amount of outdoor space are: elevated
Terraces, patios, verandas, balconies, yards,
decks, and roof gardens.

3. Design. The common open space area must
be open to the sky, except for any allowable
Encroachments (see Section 3.8) and any Shade
Structures within the space.

J. Landscape

1. All outdoor space shall be landscaped or
Hardscaped.

2. At least 25 percent of the required on-site
outdoor space shall be planted with ground
cover, shrubs, trees, or a combination thereof.

Page 397 of 618 ends

27 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

2.3.6 Carriage House
A. Intent Statement
A structure composed of residential units above
at least partially-enclosed ground-floor parking
spaces. The parking is accessed from an alley or
surface parking lot, while the residential units are
accessed from the street or pedestrian path. The
residential space need not be directly connected
to the parking. Especially suitable as liner
buildings, carriage houses can be used to screen
surface parking lots from the primary street.

Garden Style Apartments are most similar to this
Building Type.

B. Applicability
All multifamily and mixed-use zones.

C. Façade Width
Maximum Façade Width is 120 feet.

D. Building Height & Massing

1. Maximum Height: Three stories.

2. The second and third stories may occupy the
full ground floor Footprint area, so long as it is
within the Floor Area Ratio (FAR) allowed for
that zoning district.

3. Façade Strings shall have at least one
Encroachment per 100 linear feet, such as a
porch, balcony, or Plane Break. The combined
length of Plane Breaks shall occupy at least ten
percent of the Façade length.

4. Building Faces abutting side streets or yards
shall provide at least one Horizontal Plane
Break of at least three feet, and one vertical
Plane Break of at least two feet.

E. Maximum Upper-Level Frontage
Occupancy
Not applicable.

F. Frontage Types

1. Permitted Frontage Types: Front Porch, Stoop,
and Raised Residential Terrace. (See Sections

4.5, 4.7, 4.9)

2. Front Setbacks per Zoning Standards.

3. A carriage house’s ground floor shall be
designed so that the street-facing side appears
to be habitable.

G. Pedestrian Access & Entries

1. The Primary Entrance to the building shall be
accessed directly from and face the street or
pedestrian path.

2. A secondary entrance may be provided from
the rear parking spaces.

3. Parking and services shall be accessed through
the alley or surface parking lot.

BUILDING TYPE STANDARDS • CARRIAGE HOUSE
Figure 2-20 - Carriage House Diagram
MAX 120’

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 28 Figure 2-22 - Carriage House Illustrative Photo
Figure 2-21 - Concept Rendering of Carriage House
H. Parking

1. Parking spaces shall face the alley or surface
parking lot and be screened from view from the
side street by a garden wall, fence or hedge.

2. Tandem spaces are permitted.

3. Parking spaces do not have to correspond with
the residential unit above.

4. Parking spaces do not need to be fully enclosed.

5. Services, utilities, and trash container areas
shall be located on the alley or in the surface
parking lot.

I. Common Open Space
Not required.

J. Landscape
To the extent it is provided, an outdoor space shall
be landscaped or Hardscaped.

BUILDING TYPE STANDARDS • CARRIAGE HOUSE

Page 399 of 618 ends

29 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

2.3.7 Small Mixed-Use Building
A. Intent Statement
A low-scale building that includes ground-floor
non-residential uses such as retail, service, or
office, with one or more residential uses located
on the upper floors. This Building Type is intended
for sites fronting commercial corridors or
neighborhood centers and is typically two to three
stories in Height.

B. Applicability
Mixed-use zones only.

C. Façade Width
Maximum Façade Width is 100 feet.

D. Building Height & Massing

1. Maximum Height: 45 feet.

2. The upper stories may occupy the full ground
floor Footprint area.

E. Maximum Upper-Level Frontage
Occupancy
Not applicable.

F. Frontage Types

1. Permitted Frontages: Stoop, Shopfront and
Raised Commercial Terrace. (See Sections 4.3,

4.4, 4.5)

2. Ground-floor Façades shall include retail, office,
or work space uses that occupy at least 50
percent of the ground-floor depth and extend
across a minimum of 60 percent of the primary
Façade Width. At least 60 percent of the
primary ground-floor Façade between two and
ten feet above Sidewalk Grade shall consist of
transparent windows that provide direct views
into the occupied space.

G. Pedestrian Access & Entries

1. Primary access to ground-floor spaces shall be
directly from the street.

2. Building and retail entrances fronting primary
and side streets shall remain accessible and
unlocked during regular business hours.

3. Primary Entrances to upper floors shall be
accessed through:
• Entrance in the rear.
• A lobby that is accessed directly from the
street.
• Stoops entered from the street.

H. Parking

1. Parking shall be an alley-loaded lot and/or
parallel on-street.

BUILDING TYPE STANDARDS • SMALL MIXED-USE BUILDING
Figure 2-23 - Small Mixed-Use Building Diagram
MAX 100’
45’
MAX

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 30

2. Where no alley is present, parking may be
accessed via a Driveway and from the primary
and/or secondary street. Such Driveways may
include parking along one side, making the total
parking area exposed to the street no greater
than 45 feet. Parking spaces shall be screened
from view from the fronting street, by a low
wall, fence or hedge consistent with DBCC
Section 22.16.080 (5). (See Figure 2-24)
I. Common Open Space
Not required.

J. Landscape
See DBCC Chapters 22.24, 22.26 and Section

22.20.070 for parking lot landscaping standards.

BUILDING TYPE STANDARDS • SMALL MIXED-USE BUILDING
Figure 2-25 - Small Mixed-Use Building Illustrative Photo Figure 2-24 - Small Mixed-Use Building Diagram
26’
MIN

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31 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING TYPE STANDARDS • COURTYARD MULTIFAMILY BUILDING

2.3.8 Courtyard Multifamily Building
A. Intent Statement
A grouping of Townhouses, walkups, or other
multifamily buildings arranged on a site around a
central courtyard or series of courtyards at grade
or above a parking Podium. The building may
contain residential, commercial, or a combination
of these uses. Parking is provided below ground or
accommodated in up to two above-grade Podium
Levels.

B. Applicability
All multifamily and mixed-use zones.

C. Façade Width
The maximum length of any portion of the Façade
that sits along a Build-to-Line shall not exceed 75
feet.

D. Building Height & Massing

1. Maximum building Height shall comply with
the Height limits of the underlying zoning
district, but shall not exceed 65 feet under any
circumstance, including where greater Heights
are permitted for other Building Types within
the same zone.

2. The maximum length of the entire courtyard
ensemble shall not exceed 225 feet. This
includes the building mass plus the side of the
courtyard that is open to the Frontage.

Table 2-2:

Height in
Stories
Maximum Allowed Footprint per
Story
1-2 3 4 5
2 100% - - -
3 100% 80% - -
4 100% 100% 80% -
5 100% 100% 80% 80%
E. Maximum Upper-Level Frontage
Occupancy
Portions of Façades above 45 feet in Height and
greater than 150 feet in length shall occupy no
more than 80% of the Primary Façade Plane
established on the ground floor.

F. Frontage Types
Permitted Frontage Types are: Forecourt,
Shopfront, Raised Commercial Terrace, Urban
Frontage, and Dooryard. (See Sections 4.3, 4.4, 4.6,

4.8, 4.10)
G. Pedestrian Access & Entries

1. The internal courtyard shall be accessible from
the street, through the Frontage. If the internal
courtyard is located above the Ground Plane, a
public stair, with treads and risers at least eight
feet in width, and incorporating Architectural
Features consistent with the building’s
Architectural Style is required. Access may be
gated.

2. The Primary Entrance to each ground-floor unit
shall be directly from the street or courtyard.

Entrances shall occur at a maximum interval of
60 feet.

3. Primary access to units above the ground floor
shall be through a lobby accessed from the
street or the courtyard.
55’
MAX
75’ MAX
225’ MAX
Figure 2-26 - Courtyard Multifamily Building Diagram

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 32 Figure 2-27 - Courtyard Building Illustrative Photo
Courtyard View of a Courtyard Building
H. Parking

1. Parking may be accommodated in surface lots
with or without tuck under parking or in two
levels of above-ground Podium or below ground
parking or both.

2. A liner of habitable space shall conceal aboveground Podium parking garages from view.

3. Residential parking shall be separate from
retail parking, except for any residential guest
parking.

I. Common Open Space

1. Amount required. At least 15 percent of the Lot
Area shall be provided as common open space.

2. Types. Permitted common open space types
that count toward the satisfaction of the
required amount of common open space are:
patios, verandas, and courtyards.

3. Dimensions. The minimum courtyard dimension
shall be 30 feet on each side for buildings. If the
courtyard is surrounded by three or more sides
or if the building is three or more stories, the
minimum dimension on each side shall be 40
feet.

4. Encroachments. Encroachments into the
common open space are permitted on all sides,
provided that the minimum 30-foot dimension
is maintained, exclusive of the Encroachments.

5. Design. The common open space area must
be open to the sky, except for any allowable
Encroachments (see Section 3.8) and any Shade
Structures within the space.

J. Landscape

1. All outdoor space shall be landscaped or
Hardscaped.

2. At least 25 percent of the required on-site
common open space shall be planted with
ground cover, shrubs, trees, or a combination
thereof.

BUILDING TYPE STANDARDS • COURTYARD MULTIFAMILY BUILDING

Page 403 of 618 ends

33 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING TYPE STANDARDS • WRAP BUILDING
Garage
Wrap
Primary Street
Side Street

2.3.9 Wrap Building
A. Intent Statement
A building and garage ensemble where the building
directly fronts the street and wraps around an
above-ground garage. The building may contain
residential, commercial, or a combination of these
uses. The garage may either be attached to or
detached from the building.

B. Applicability
Mixed-use zones only.

C. Façade Width

1. Maximum 250 feet.

2. Blank walls (defined as having no active use,
glazing or doorway) shall be limited to 20% or
40 feet of the Building Façade, whichever is less
along all required streets. This requirement is
not applicable for Façades along service or fire
lanes and alleys.

D. Building Height & Massing

1. The maximum Height shall comply with the
Height limits of the underlying zoning district,
but shall not be less than 35 feet, nor exceed 75
feet under any circumstances, including where
greater Heights are permitted for other Building
Types within the same zone.

2. The maximum garage Height shall be 55 feet
excluding shading devices or photovoltaic
panels.

3. The maximum allowed Footprint per Story shall
be determined by the following table:

Table 2-3:

Height in
Stories
Maximum Allowed Footprint per
Story
1-2 3 4 5
2 100% - - -
3 100% 90% - -
4 100% 90% 75% -
5 100% 100% 85% 75%
E. Maximum Upper-Level Frontage
Occupancy
Portions of Façades above 55 feet in Height and
greater than 150 feet in length shall occupy no
more than 70% of the Primary Façade Plane
established on the ground floor.

F. Frontage Types
Permitted Frontage Types are Forecourt, Shopfront,
Raised Commercial Terrace, Raised Residential
Terrace, Urban Frontage, Stoop, and Dooryard. (See
Sections 4.3, 4.4, 4.5, 4.6, 4.8, 4.9, 4.10)
G. Pedestrian Access & Entries

1. Primary Entrances to upper floors shall be
accessed through an interior courtyard or lobby,
accessed directly from the street.

2. Primary access to the ground-floor residential
space shall be directly from the street.

3. All retail spaces shall be accessed from a
ground-floor, single-tenant entry along a street,
courtyard, or Paseo.

Figure 2-28 - Wrap Building Diagram
250’ MAX
75’
MAX

Page 404 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 34 Figure 2-29 - Wrap Building Illustrative Photo
Street view of a linear building. The Façade does not reveal the parking use behind.

BUILDING TYPE STANDARDS • LINEAR BUILDING WITH GARAGE

4. Primary retail entrances shall remain accessible
and unlocked during regular business hours.

5. In addition to the building’s required Primary
Entrances, there may be ancillary entrances to
the building from parking garages.

H. Parking
Not applicable.

I. Common Open Space

1. Amount required. At least 10 percent of the Lot
Area shall be provided as common open space.

2. Types. Permitted common open space types
that count toward the satisfaction of the
required amount of common open space are:
patios, verandas, courtyards, and roof gardens.

3. Dimensions. Each common open space shall
have a minimum dimension of 20 feet on each
side.

4. Encroachments. Encroachments into the
outdoor space are permitted on all sides,
provided that the minimum 20-foot dimension
is maintained, exclusive of the Encroachments.

5. Design. The common open space area must
be open to the sky, except for any allowable
Encroachments and any Shade Structures
within the space.

J. Landscape

1. All common oopen space shall be landscaped or
Hardscaped.

2. At least 25 percent of the required on-site
common open space shall be planted with
ground cover, shrubs, trees, or a combination
of thereof. Landscaping in pots or Planters may
be included in computing the total Landscaped
Area.

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35 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING TYPE STANDARDS • URBAN BLOCK

2.3.10 Urban Block
A. Intent Statement
A building designed for occupancy by retail,
service, office, and/or residential uses on the
ground floor, with upper floors also configured
for office and/or residential uses, however twoStory retail is permitted. Parking is usually accommodated below ground.

B. Applicability
Mixed-use zones only.

C. Façade Width

1. Maximum is 225 feet.

2. Blank walls (defined as having no active use,
glazing or doorway) shall be limited to 20% or
40 feet of the Building Façade, whichever is
less, along all required streets. This requirement
is not applicable for Façades along service or
fire lanes and alleys.

D. Building Height & Massing

1. Maximum Height: 75 feet.

2. The maximum allowed Footprint per Story shall
be determined by the following table:

Table 2-4:

Height in
Stories
Maximum Allowed Footprint per
Story
1-2 3 4 >5
2-3 100% - - -
4-5 100% 85% 75% -
>5 100% 100% 85% 75%
E. Maximum Upper-Level Frontage
Occupancy
Portions of Façades above 55 feet in Height and
greater than 150 feet in length shall occupy no
more than 70% of the Primary Façade Plane
established on the ground floor.

1. Primary Entrances to upper floors shall be
accessed through: 1. an interior courtyard or

2. a lobby, which is accessed directly from the
street.

2. Primary access to the ground-floor residential
space shall be directly from the street.

3. All retail spaces shall be accessed from a
ground floor single tenant entry along a street,
courtyard or paseo, remain accessible and
unlocked during regular business hours.

Figure 2-30 - Urban Block Diagram
75’
MAX
225’ MAX

Page 406 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 36 BUILDING TYPE STANDARDS • URBAN BLOCK
Figure 2-31 - Urban Block Illustrative Photo
Figure 2-32 - Urban Block Illustrative Photo
H. Parking

1. Parking may be accommodated in up to two
levels of above-ground Podium, below ground,
or both.

2. A liner of habitable space shall conceal aboveground Podium parking garages from view.

I. Common Open Space

1. Amount required. At least 15 percent of the Lot
Area shall be provided as common open space.

2. Types. Permitted common open space types
that count toward the satisfaction of the
required amount of common open space are:
patios, verandas, courtyards, and roof gardens.

3. Dimensions. Each common open space shall
have a minimum dimension of 20 feet on each
side.

4. Encroachments. Encroachments into the
common open space are permitted on all sides,
provided that the minimum 20-foot dimension
is maintained, exclusive of the Encroachments.

5. Design. The common open space area must
be open to the sky, except for any allowable
Encroachments and any Shade Structures
within the space.

J. Landscape

1. All common open space shall be landscaped or
Hardscaped.

Page 407 of 618 ends

37 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING TYPE STANDARDS • MIXED-USE BIG BOX

2.3.11 Mixed-Use Big Box
A. Intent Statement
This Building Type provides additional flexibility
for developments incorporating a supermarket or
other large format retailer.

B. Applicability
Mixed-use zones only.

C. Façade Width

1. Maximum 300 feet.

D. Building Height & Massing

1. Maximum building Height shall comply with
the Height limits of the underlying zoning
district, but shall not exceed 75 feet under any
circumstance, including where greater Heights
are permitted for other Building Types within
the same zone.

2. Minimum Height is 55 feet.

3. The maximum retail floor plate is 65,000 sf.

4. The maximum allowed Footprint per Story shall
be determined by the following table:

Table 2-5:

Height in
Stories
Maximum Allowed Footprint per
Story
1-3 4 5
2-3 100% - -
4 100% 90% -
5 100% 90% 75%
E. Maximum Upper-Level Frontage
Occupancy
In zoning districts where such Heights are
permitted, portions of Façades above 45 feet in
Height and greater than 150 feet in length shall
occupy no more than 80% of the Primary Façade
Plane established on the ground floor.

1. Primary Entrances to upper floors shall be
accessed through a lobby, accessed directly
from the street or from a courtyard.

2. Primary access to the ground-floor retail space
shall be directly from the street and shall occur
at a maximum interval of 60 feet. Retailers over
30,000 sf must have at least two entrances.

Figure 2-33 - Mixed-Use Big Box Diagram
300’ MAX
75’
MAX

Page 408 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 38 BUILDING TYPE STANDARDS • MIXED-USE BIG BOX

3. All retail spaces shall be accessed from a
ground-floor, single-tenant entry along a street,
courtyard, or alley.

4. Primary retail entrances shall remain accessible
and unlocked during regular business hours.

5. In addition to the building’s required Primary
Entrances, there may be ancillary entrances to
the building from parking garages.

H. Parking

1. Above-ground garages shall be concealed from
view along the street for the first 21 feet of
Height through a liner of habitable space.

2. Above 21 feet, above-ground garages shall
be screened from view along the street by
habitable space or by landscaping, outdoor
screens, or cladding.

I. Common Open Space
Not required.

J. Landscape
All outdoor space shall be landscaped or
Hardscaped. See DBCC Chapters 22.24, 22.26 and
Section 22.20.070 for parking lot landscaping
standards.

Figure 2-34 - Mixed-Use Big Box Illustrative Photo
Figure 2-35 - Mixed-Use Big Box Illustrative Photo

Page 409 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 3 BUILDING

ARTICULATION

STANDARDS

Page 410 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 40 BUILDING ARTICULATION STANDARDS • PURPOSE

BUILDING ARTICULATION

STANDARDS

3.1 Purpose
The desired pedestrian scale and character of Diamond Bar requires that new project development not appear as massive, monolithic structures, but instead as a series of smaller scale buildings. The standards of this section are intended to ensure that larger projects are designed to appear as carefully conceived groups of separate structures that, along with an attractive streetscape, contribute to the overall urban, pedestrianfriendly quality desired for Diamond Bar.

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41 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Page Left Intentionally Blank

Page 412 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 42 Figure 3-1 - Multiple Variations of Same Style Figure 3-2 - Mixed-Use Building Articulated with Corner

3.2 Building Articulation Techniques
Min. Number
of Building
Articulation
Techniques
Façade Length
≤ 50 ≥ 50-
100
≥ 100-
100
≥ 150
1 X
2 X
3 X
4 X
The table above outlines the minimum number of
building articulation techniques—listed below—that
must be applied based on the building’s Façade length:

1. Horizontal Articulation

2. Vertical Articulation

3. Architectural Projections

4. Architectural Recessions

5. Façade Differentiation

6. Architectural Style Differentiation

7. Base, Middle, and Top Articulation
BUILDING ARTICULATION STANDARDS • BUILDING ARTICULATION TECHNIQUES Table 3-1: Building Articulation
Standards Matrix

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43 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING ARTICULATION STANDARDS • DIAGRAMS

1. Horizontal Articulation
Step a portion of the street-facing
Façade forward or backward from the
predominant Façade Plane a minimum
of six feet for a minimum distance of
25 feet.

2. Vertical Articulation
Step a portion of the street-facing
Façade upward or downward from
the Predominant Building Height a
minimum of four feet for a minimum
distance of 25 feet. This technique
is useful for “stepping down” the
scale of a new building adjacent to an
existing smaller building.

3. Architectural Projections
Append or project balconies, bay
windows, cantilevered rooms, roof
overhangs or Eaves and/or awnings.

Provide at least one Projection of at
least two feet in depth and three feet
in width per every 50 feet of Façade
length.

Figure 3-3 - Horizontal Articulation Diagram
Figure 3-4 - Vertical Articulation Diagram
Figure 3-5 - Architectural Projections Diagram
25’
MIN
25’ MIN
4’
MIN
6’ MIN

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 44 BUILDING ARTICULATION STANDARDS • DIAGRAMS

4. Architectural Recessions
Recess Architectural Features or
spaces - such as porches, covered
passages, balconies, and windows -
into the plane at intervals of 50 feet
on center along the Façade length.
a.Porches, covered passages, and
balconies must be recessed by
a minimum of six feet from the
front plane of the Façade to be
considered a recession.
b.Windows must be recessed by a
minimum of five inches from the
front plane to be considered a
recession.

5. Façade Differentiation
Organize the Façade with two or three
distinct compositions. Distinctions
may include material and/or color
combinations for each apparent
Façade. A change in the length of a
composition does not constitute a
distinct composition.

6. Architectural Style
Differentiation
Design the Façade to include at least
two Architectural Styles (from Chapter
6), with no one style occupying less
than 30 percent of the total Façade.

Style 1
Style 2
Style 3
Concept 1
Concept 2
Concept 3
Figure 3-8 - Architectural Style Differentiation Diagram Figure 3-7 - Façade Differentiation Diagram
Figure 3-6 - Architectural Recessions Diagram

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45 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING ARTICULATION STANDARDS • DIAGRAMS

7. Base, Middle, and Top
Articulation
A. Compose Building Façades with a
Base, Middle, and Top on any street
or paseo facing Façade.

B. Buildings shall have a distinct
“base” at the ground level whose
Height is 10 percent to 35 percent
of the building’s total Height, and
may include the ground floor
(or part of the ground floor) and
lower structural components
that connect the building to its
site. This may be accomplished
with distinct materials, or distinct
application of materials, and/or a
horizontal expression line, such as
a Water Table or Cornice, creating a
transition to the upper floors. This
feature shall extend across at least
80 percent of the Façade length.

C. The middle of the building shall
have a Height comprising from
50 percent to 87 percent of the
building’s total Height.

D. The top of buildings include
articulation at the Parapet (for
buildings with flat roofs) and/or the
top floor, or below the Eave (for
buildings with sloped roofs) that
identifies the top of the building
with a Cornice, color change, or
material change. The top of the
building shall have a Height of three
to 10 percent of the building’s total
Height, but shall be less than the
Height of the building base.

Base
10-35%
Top
3-10%
Cornice
Middle
50-87%
Total 100%
Figure 3-9 - Base Middle and Top Articulation Diagram
Water Table

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 46 BUILDING ARTICULATION STANDARDS • TRANSITION TO RESIDENTIAL DISTRICTS & ENTRANCES Figure 3-10 - Illustrative Diagram
A
B
C
A.

3.3 Transition to Single-Family Residential
Districts
Where new mixed-use or multifamily development
is adjacent to property developed with single-family
residences or zoned for single-family residential use,
the following standards shall apply:
a.Height Envelope. No portion of a new structure
shall extend above a plane starting at 30 feet in
Height at the shared property line and projecting
inward at a 45-degree angle from vertical toward
the interior of the site, up to the maximum
permitted building Height (see Figure 3-10).
b.Reference Grade. The 30-foot measurement shall
be taken from the finished grade of the adjacent
single-family residential property (or single-family
residentially zoned parcel), not from the grade of
c.Architectural Style Restriction. The California
Contemporary Style (see Section 6.6) shall not be
permitted adjacent to Single-Family Residential
Districts.

3.4 Entrances

1. Primary Entrance. The Primary Entrance to
buildings shall be in conformance with the
requirements of the Building Type in Chapter 3.

2. Entrance Articulation. Special Paving, lighting,
and landscaping shall be included at Primary
Entrances to clearly identify the entrance and
to enhance the overall building design.

Figure 3-11 - Entrances
A canopy, lighting, and a slight recess accentuate the Primary Entrance.

Property Line

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47 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

3.5 Passageways

1. Pedestrian passageways shall be no less than 15
feet wide.

2. If pedestrian passageways are covered, they
require a floor to ceiling Height of at least two
times their width, but no greater than three
times their width.

3. Passageways shall be lighted.

3.6 Windows

1. Design shall be according to the requirements
of the Architectural Style in Chapter 7.

2. Glazing Transparency and Reflectance. All
ground-floor and street-facing window glazing
must have a Visible Light Transmittance (VLT)
of at least 60%, and an Exterior Reflectance
(ER) of no more than 15%. Highly reflective,
mirrored, or heavily tinted glazing is prohibited.

Opaque glazing may only be used as spandrel
glass or where required for mechanical
screening or privacy.

BUILDING ARTICULATION STANDARDS • PASSAGEWAYS & WINDOWS & ROOD STANDARDS Figure 3-12 - Windows
Windows are recessed from the exterior wall surface.

Figure 3-13 -Variety of Rooflines Illustrative Photo
Apartment complex with a variety of rooflines.

3.7 Roof Standards

1. The roof edge shall be defined with a Parapet,
Cornice, and overhang.

2. Rooftop mechanical equipment shall be
clustered away from the edge of the building
and behind/within an enclosure to be screened
from the street.

3. Unenclosed Shade Structures, and similar
amenities shall not exceed 16 feet in Height
from the roof deck floor level and do not count
as a Story.

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 48

3.8 Encroachments and Projections
The following are the permitted Encroachments and
Projections into the front Setbacks.

A. Awning and Canopy Encroachment and
Projection Standards

1. Projection. May project up to the right-of-way
line or 33 percent of the distance between the
Building Face and the curb, whichever is less.

2. Support. Awnings and canopies shall be
attached to the building. Support structures
that connect to the ground are not permitted.

3. Clearance. Minimum vertical clearance
for awnings and canopies is 10 feet if it is
removable or retractable and 12 feet if it is
fixed or permanent. Awnings shall not obscure
storefront signs.

4. Materials. Awnings and canopies shall be
constructed of canvas, durable woven fabric, or
metal, and shall be consistent with the materials
and detailing associated with the building’s
selected Architectural Style, as specified in
Chapter 6. Vinyl, plastic, and visibly glossy or
reflective materials are prohibited. Colors shall
align with the approved color palette for the
selected style. Translucent or backlit awnings
are prohibited. Awnings and canopies shall be
designed as integral components of the building
and shall not appear as temporary or tacked-on
features.

5. Heights of awnings on a building shall be the
same along the Façade or Frontage line unless
the building steps in relation to grade, in which
case, the Heights of awnings shall be consistent
with the head Heights of the windows and doors
they are shading.

B. Habitable Projecting or Encroaching Interior
Space Standards

1. Allowable Projection. Habitable projecting or
encroaching interior spaces are a portion of
the building enclosed by walls and a roof that
extends beyond the Building Face (i.e. bay
windows and other architectural Projections).

They may project up to three feet from the
Building Face, but shall not extend beyond the
property line.

2. Length Along Building Face. No individual
habitable projecting or encroaching interior
space may exceed 15 feet in horizontal length.

3. Clearance. Minimum vertical clearance of upper
Story projecting spaces shall be 16 feet from
the adjacent Sidewalk Grade on storefront
or storefront Terrace Frontages or 10 feet
above other Frontage Types (see Chapter 4 for
Frontage Types).

C. Habitable Projecting or Encroaching
Exterior Space Standards

1. Balconies. Usable projecting or encroaching
exterior spaces are spaces used by occupants
that are not enclosed by walls and a roof, such
as balconies. They shall not extend more than
eight feet from the Building Face, or beyond
the right-of-way line. Unless permitted by the
Architectural Style, projecting balconies shall be
no less than six feet in depth. Balconies shall be
accessible from inside the building and shall not
be completely enclosed.

2. Clearance. The minimum vertical clearance
of non-habitable projecting or encroaching
exterior spaces is 16 feet from the adjacent
Sidewalk Grade above storefront Frontages
or 10 feet above other Frontage Types (see
Chapter 4 for Frontage Types).

Figure 3-14 - Encroaching Habitable Space
Illustrative image of encroaching bays and Stoops.

BUILDING ARTICULATION STANDARDS • ENCROACHMENTS AND PROJECTIONS

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49 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development F. Stoops

1. Stoops may encroach into the front Setback Area
but shall not extend beyond the property line.

G. Outdoor Furnishing Zones

1. Outdoor display/sales of merchandise may not
encroach into Setback areas per DBCC Section

22.42.080 (2)(b).

2.Outdoor furnishing zones shall comply with DBCC
Section 22.42.080 (3)(d).

3.General. Outdoor furnishings such as seating or
merchandise displays shall comply with Sections

5.3 and 5.4.

H. Subterranean Parking in Front Setbacks

1. Location in Setbacks & Alleys. Subterranean
parking may extend into the front Setback, up to
the property line (See Figure 3-16). Subterranean
parking may also be located under alleys that
are located within a development Block if utilities
servicing the Block are not interrupted.

Figure 3-16 - Encroachment and Projections Diagram
A. Projecting habitable space
B. Projecting canopy
C. Encroaching street furniture
D. Subterranean parking (purple area)
Property Line
A
C
B
D
Encroachment /
Projection Area
Building
Face
BUILDING ARTICULATION STANDARDS • ENCROACHMENTS AND PROJECTIONS CONTINUED D. Interior and Exterior Projecting Habitable
Space Standards

1. Total Horizontal Length of Projecting Spaces.

The total combined length of habitable interior
and exterior projecting spaces along the
Building Face shall not exceed 67 percent of the
total length of the Building Face to which they
are attached.

2. Total Horizontal Length of Encroaching Spaces.

The total combined length of habitable and
Non-Habitable Encroaching Spaces along the
Building Face shall not exceed 50 percent of the
total length of the Building Face to which they
are attached.

E. Rooftop Amenities

1. Rooftop amenities such as swimming pools are
permitted; rooftop amenities do not count as a
Story.

Figure 3-15 - Projecting Canopies
Canopies create a rhythm along the streetfront and
accentuate the building entrances.

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 50 BUILDING ARTICULATION STANDARDS • SHOPFRONTS IN MIXED-USE BUILDINGS Figure 3-17 -Illustrative Photo of Shopfronts in Mixed-Use Buildings
Architecturally-consistent detailing from signage and lighting fixtures, to colors and materials, enhance the character of the streetscape.

3.9 Shopfronts in Mixed-Use Buildings

1. Shopfronts shall have paving that is unique to
the area in front of the shop within the Setback
area, in order to differentiate the building
entrance, but shall be designed with primary
consideration of the public right-of-way.

2. Shopfronts along ground floor commercial
spaces shall provide windows that constitute at
least 60 percent of the Façade area of the shop
itself, measured from the ground to the secondfloor line, and from centerline to centerline of the shop’s demising wall.

3. Where multiple retail tenants occupy one
building, the same Height of awnings across
an entire building shall be maintained. Building
or Shopfront entries along the ground floor
shall be equidistant, if feasible. Shopfronts
shall be designed to be subdivided at 30-foot
intervals for commercial leasing flexibility
and functionality and to create a fine-grained
rhythm along the Street.

4. Blank Walls shall not be permitted along the
Principal Frontage of large tenant spaces on the
ground floor of mixed-use buildings.

5. Multiple entrances shall be incorporated for
large stores along a Street front whose length
spans the width of more than two typical shops
(2 X 30 ft), or which front on more than one
Street.

6. Rather than shadow window box displays,
at least 65 percent of a retail Frontage shall
include transparent glazing and at least 70
percent of the glazing shall allow views into the
store. Mirrored or opaque films on windows that
Block views into the store are not permitted.

7. A base below windows shall be between 18-30
inches in Height to protect glazing from foot
traffic, while maintaining the characteristic of
Height and openness.

8. Commercial grade entry doors with clear
glazing framed in metal or wood shall be used.

9. Shopfronts shall use awnings, canopies,
architectural lighting, and pedestrian signage to
articulate shop entrances.

Figure 3-18 - Minimum Frontage Glazing Diagram
The Frontage glazing area shall be measured from the
finished floor to the bottom of ceiling of the ground floor.

Frontage Width
Bottom
of interior
ceiling
Frontage Height
Glazing Area

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51 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development BUILDING ARTICULATION STANDARDS • COLORS AND MATERIALS

3.10 Colors and Materials

1. Changes of exterior color, texture, or material
shall be accompanied by changes in plane so
that buildings appear substantial and integral.

2. Color and material changes at the outside of
corners of a building or plane change that
give a Thin Veneer, or Faux Stone Appearance,
shall not be used. Where the color or material
extends to an outside corner, it shall continue
around the corner to the next inside corner.

Figure 3-19 - Changes of Colors and Materials Illustrative Photo
Changes of exterior color, texture, or material shall be accompanied by changes in plane so that buildings appear substantial and integral.

Page 422 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 52 Page Left Intentionally Blank

Page 423 of 618 ends

FRONTAGE
TYPES
Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 4

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 54 FRONTAGE TYPES • STANDARDS AND GUIDELINES

FRONTAGE TYPES

4.1 Purpose and Intent
A building’s Frontage is the interface between the Public Realm and private development. These standards recognize that the successful design of this interface significantly contributes to the realization of an active and engaging urban environment.

Multifamily and mixed-use buildings will have ground-floor Frontages that are human-scaled, provide visual interest, and access to ground-floor uses. This section provides a palette of prototypical Frontage Types that are permitted. Standards include dimensional criteria, criteria for openings, as well as criteria for the Ground Plane immediately adjacent to the Frontage, such as minimum required glazing.

Intent:

In order for applications to be approved, each application shall meet the following criteria as applicable:
a.Creates or maintains a pedestrian-oriented streetscape, b.Generates a transition from the public streetscape to each building and its site.

The standards that follow provide objective and measurable standards that, when applied to the design of Frontages, fulfill this intent.

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55 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development FRONTAGE TYPES • EXPLANATION OF STANDARDS

4.2 Explanation of Standards
This chapter provides standards for the following eight Frontage Types.

For each Frontage Type, the standards described
below are provided. See Table 4-1 for a summary of
Frontage Types.

It is possible to utilize more than one Frontage along
the length of a Building Face.

A. Frontage Intent Statement
This statement describes the building-to-street
relationship that each Frontage Type is meant to
achieve.

B. Entries
These standards address entries at the street or paseo
fronts, not those that are internal to the site, or on
alleys.

C. Dimensions
Specific dimensions of features like massing, entry
Height, openings, and Setbacks are delineated here.

D. Paving and Landscaping
This standard addresses the area between the
property line and Building Face. Where paving is
specified, it shall match the paving of the fronting
sidewalk or consist of Special Paving. Where landscape
is required, it shall conform to Section 5.5 of these
standards.

E.Furnishing Zone
This standard addresses furnishing within front
Setbacks.

F. Additional Standards and Guidelines
These standards provide additional direction in
shaping the appropriate building-to-street relationship.

They address glazing at the ground floor, Frontages,
and entries.

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 56 FRONTAGE TYPES • FRONTAGE TYPE MATRIX
Frontage
Type
Typical
Setback
from Curb
Entry
Elevation
Public
Interface Typical Use Street Activation Section
Shopfronts
in Mixed-Use
Buildings
15-25ft At Grade
Direct access to
retail/commercial
space Setback
Area is Paved
Retail,Food and
Beverage mixeduseHigh 4.3
Raised
Commercial
Terrace
20-25ft 1.5-4ft
Paved Terrace.

Direct access from
sidewalk to Ter -
race is optional
Retail,Food and
Beverage Mixeduse, where
grading requires
ground floor
spaces to be
raised
Moderate 4.4
Stoop 12-27ft Raised
1-1/2 - 5ft
Setback Area is
Landscaped
Townhouses,
duplexes, apartmentsModerate 4.5
Dooryard 20-30ft
At Grade
or Slightly
Raised
Small landscaped
or paved Setback
defined by low
wall, hedge, or
fence
Townhouses,
duplexes and
Walkups
Moderate 4.6
Front Porch 18-28ft Raised
1-1/2 - 5ft
Setback area
is Landscaped.

Porch is paved and
covered. Direct
access from sidewalk to Terrace is
optional
Townhouses,
duplexes and
Walkups
Moderate/
High 4.7
Forecourt 12-20ft At Grade2ft
Recessed court,
often shared,
Courtyard may be
paved and/or landscaped. Setback
area may be paved
or landscaped
Apartments High 4.8
Raised
Residential
Terrace
15-25ft 1.5-4ft Hardscape or landscaped platform
Multifamily,
adaptive reuse Moderate 4.9
Urban
Frontage 15-25ft
At Grade
or Slightly
Raised
Paved or Landscape in Setback
area from sidewalk
Non-retail or
residential
ground floor,
(e.g., hotels,
lobbies, office
space, places of
assembly, etc)
Low 4.10
Table 4-1: Frontage Type Matrix

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57 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Figure 4-3 - Shopfronts in Mixed-Use Buildings
Illustrative Section
Ground floor uses open directly to the sidewalk.

Figure 4-1 - Shopfronts in Mixed-Use Buildings
Illustrative Photo

4.3 Shopfronts in Mixed-Use Buildings
A. Intent Statement
Shopfront Frontages provide direct access to groundfloor spaces that are located adjacent to the sidewalk.

Shopfronts are typically associated with retail uses in addition to food and beverage, but may accommodate
other uses as permitted by the Development Code.

Where permitted, Shopfront Frontages may provide
outdoor seating areas or outdoor displays or both.

B. Entries
Entries shall be set at the adjacent sidewalk or within an alcove that is adjacent to a sidewalk.

C. Dimensions

1. Shopfronts shall be between 12 and 22 feet high,
measured from the finished floor to the bottom
of ceiling of the storefront space. Storefront
spaces shall be set no more than 12 inches
above the adjacent sidewalk at the Primary
Entrance.

2. Building Faces shall be set back from the curb a
minimum of 15 feet and a maximum of 25 feet.

If a Shopfront fronts a paseo, no Setback is
required.

D. Paving and Landscaping
The Setback area between the property line and the
Building Face shall be paved with Special Paving.

E. Furnishing Zone
Furnishing Zones shall be in conformance with DBCC
Section 22.42.080 and Sections 5.3 and 5.4 of this
document.

Notwithstanding the statement above, outdoor seating
may be provided in front Setbacks, where permitted.

Product displays (e.g. flowers, food, merchandise
displays) are encouraged near Shopfront entries.

FRONTAGE TYPES • SHOPFRONTS IN MIXED-USE BUILDINGS
Figure 4-2 - Shopfronts in Mixed-Use Buildings
Conceptual Plan
12’-22’
15’-25’
Setback Area shall be
paved
Sidewalk
Property Line
Property Line

Page 428 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 58 FRONTAGE TYPES • RAISED COMMERCIAL TERRACE IN MIXED-USE BUILDINGS Figure 4-6 - Raised Commercial Terrace Illustrative
Section
Figure 4-5 - Raised Commercial Terrace Conceptual Plan
Figure 4-4 - Raised Commercial Terrace Illustrative Photo

4.4 Raised Commercial Terrace in MixedUse Buildings
A. Intent Statement
Raised Terraces provide outdoor dining and seating
for ground floor commercial uses. They are to
accommodate grade changes between the adjacent
sidewalk and the finished floor. Raised commercial
Terraces are appropriate Frontages for mixed-use
buildings on sloping sites. Terraces may be accessed
from the sidewalk, but this is optional.

B. Entries
Terraces may be accessed from the building or directly
from the adjacent sidewalk.

C. Dimensions

1. Terraces may be raised up to four feet above
the adjacent sidewalk.

2. Terraces shall be at least seven feet deep.

3. Terrace fronts shall be Setback from the curb a
minimum of 13 feet.

4. Building Faces shall be set back from the curb a
minimum of 20 feet and a maximum of 25 feet.

D. Paving and Landscaping
Terraces shall be paved.

E. Furnishing Zone
Where permitted, outdoor seating may be provided
in front-Setbacks. Product displays (e.g. flowers, food, merchandise displays) are permitted near storefront
entries.

F. Additional Standards

1. Terraces shall be clearly delineated with
permeable fencing, low walls or landscaping no
higher than 42 inches.

2. The bottom of Awnings, Signs, etc. shall be
located at least 10 feet above the Terrace.

Terrace Front
Property Line
Property Line
4’ Max.
10’ Min.

Sidewalk
13’ Min. 7’ Min.
20’-25’

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59 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Figure 4-9 - Stoop Illustrative Section
The entry to a building is raised above the sidewalk.

Figure 4-8 - Stoop Conceptual Plan
Figure 4-7 - Stoop Illustrative Photo

4.5 Stoop
A. Intent Statement
Stoops are small staircases leading to the entrance
of a building. The Stoop elevation provides some
privacy between the sidewalk and ground-floor
uses. Stoops may be covered.

B. Entries
Entries fronting on public streets shall face the
public sidewalk.

C. Dimensions

1. Stoops shall be at least four feet deep and four
feet wide.

2. The top of the Stoop (the landing) shall not be
raised more than five feet above the adjacent
sidewalk.

3. Walls, fences or landscape surrounding yards
adjacent to the Stoop shall be no taller than 42
inches in Height.

4. Building Faces shall be set back from the curb a
minimum of 17 feet and a maximum of 25 feet.

D. Paving and Landscaping

1. Setback Area shall be planted with shrubs, or
other drought tolerant ground cover.

2. Walks shall be paved with concrete or Special
Paving.

3. Low retaining walls, fences, or hedges may
enclose a Dooryard. Walls and hedges shall not
exceed 42 inches in Height measured from the
adjacent sidewalk.

E.Furnishing Zone
Not permitted.

F. Additional Standards

1. Stoops may encroach into any required Front
Yard Setbacks, but not into public right-of-way
or into any public utility easement.

2. Awnings, canopies, and shed roofs may cover
Stoops.

FRONTAGE TYPES • STOOP
5’ Max.
4’
Min.
4’ Min.

Setback Area
shall be landscaped
Low Wall or
Fence
42” Max
Height
Sidewalk
17’-25’
Property Line
Property Line

Page 430 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 60 FRONTAGE TYPES • DOORYARD
Figure 4-12 - Dooryard Illustrative Section
Figure 4-11 - Dooryard Conceptual Plan
Figure 4-10 - Dooryard Illustrative Photo

4.6 Dooryard
A. Intent Statement
Dooryard Frontages provide a green buffer for
residential ground-floor uses at heavily-trafficked
thoroughfares. The Dooryard Frontages provide
privacy.

B. Entries

1. 1. Entries shall be recessed behind optional
fence and/or hedges. There shall be a break for
pedestrian access at least every 200 feet but
can be frequent, if serving Townhouses.

2. Townhouses shall have entries serving the
pedestrian accessible directly from the street.

3. Ground-floor units in multifamily buildings with
corridors may have the primary entry from a
corridor accessible from a common building
lobby, directly from the sidewalk via a Dooryard,
or both.

C. Dimensions

1. Fence, hedges or walls shall be no taller than 42
inches measured from the Sidewalk Grade.

2. Dooryards shall be 10-15 feeet in depth.

3. Building Faces shall be set back from the curb a
minimum of 20 feet and a maximum of 30 feet.

D. Paving and Landscaping
Low Wall, Hedge
or Fence

1. The Setback Area shall be paved or landscaped.

2. Walks shall be paved.

E. Furnishing Zone
Outdoor furniture is permitted in the Dooryard but not
in the Setback Area.

F. Additional Standards

1. If used, hedge shall be thick enough at maturity
to obscure the fence.

2. Fence tops shall not be visible above hedge
upon maturation of landscaping.
42” Max.

Dooryard
10’-15’
0’-4’
Sidewalk
Setback Area
20’-30’
Property Line
Property Line

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61 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Figure 4-13 - Front Porch Illustrative Photo Figure 4-15 - Front Porch Illustrative Section

4.7 Front Porch
A. Intent Statement
A roofed, unenclosed room attached to the exterior
of a building that provides a physical transition
between the sidewalk and the building. Porches may
be provided on buildings that are set back from the
primary and/or side street property lines and may
encroach into the Front Yard and side street yard
pursuant to DBCC Section 22.16.090 (3)(c).

B. Entries
Porches may be accessed directly from the adjacent
sidewalk along the primary and/or side street.

C. Dimensions

1. Porches shall be a minimum of six feet in depth.

2. The face of porch may be set back from the
property line up to 15 feet maximum.

3. Ceiling Height on porches shall be a minimum of
eight feet.

4. Where porches are set back from the Frontage
line by at least 10 feet, the space between the
face of the porch and the Frontage line (yard)
may be enclosed by a fence, hedge or wall of a
Height no greater than 42 inches above finished
grade.

5. Building Faces shall be set back from the curb a
maximum of 28 feet.

D. Paving and Landscaping

1. The Setback Area between the property line
and the building front shall be landscaped.

2. Walks shall be paved.

E. Furnishing Zone
Not applicable.

F. Additional Standards

1. Porch materials and design shall be of the same
Architectural Style as the rest of the building.

2. Porches may be enclosed with insect screens,
provided they are recessed from the exterior
wall plane and if visibility is maintained from the
sidewalk.

FRONTAGE TYPES • FRONT PORCH
Figure 4-14 - Front Porch Conceptual Plan
6’ Min.
8’
Min.
5’ Max.
15’ Max.
15’ Max.
21’ Max.
28’ Max.
6’ Min.

Property Line
Property Line
Sidewalk

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 62 FRONTAGE TYPES • FORECOURT
Figure 4-17 - Forecourt Conceptual Plan
Figure 4-16 - Forecourt Illustrative Photo

4.8 Forecourt
A. Intent Statement
Forecourts are open areas located at primary building
entrances. They may be designed as gardens or as
paved courtyards. Frontages utilizing a Forecourt must
comply with Minimum Frontage Occupancy standards.

B. Entries
Ground-floor units in multifamily buildings with a
Forecourt shall enter from the adjacent sidewalk.

Building entries opening onto the Forecourt shall be at the finished floor of the Forecourt or may be raised up to three feet above the Forecourt.

C. Dimensions

1. Forecourts shall be set at grade or may be
elevated up to two feet above the adjacent
sidewalk.

2. Width of the Forecourt shall be between 30 and
50 feet.

3. Depth of the Forecourt shall be minimum 10
feet.

4. Building Faces shall be set back from the curb a
minimum of 12 feet and a maximum of 20 feet.

D. Paving and Landscaping

1. Forecourts may be planted with grass, shrubs,
or other ground cover or be paved. Special
paving shall be provided for all walks.

2. Setback areas shall be landscaped.

E. Furnishing Zone

1. The courtyard may include benches, chairs,
tables, Planters and pots.

2. Water Features are permitted.

F. Additional Standards

1. Forecourts shall be open to the sky. Porches are
permitted as long as the minimum 30 feet width
is maintained.

2. Forecourts may be gated. If gated, the
standards for gates shall be in conformance
with the Development Code.

Setback Area may be paved or
landscaped
Sidewalk
30’-50’
10’ Min
12’-20’
Figure 4-18 - Forecourt Illustrative Section
The building entry is located off a Forecourt. The entry may or may not be raised above the sidewalk level.

Property Line
Property Line
2’ Max

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63 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development FRONTAGE TYPES • RAISED RESIDENTIAL TERRACE
Figure 4-19 - Raised Residential Terrace Illustrative Photo Figure 4-21 - Raised Residential Terrace Illustrative Section
Figure 4-20 - Raised Residential Terrace Conceptual Plan

4.9 Raised Residential Terrace
A. Intent Statement
An elevated Terrace separates and sets back the
Façade from the sidewalk and street. This type buffers
residential use from urban sidewalks and removes
the private yard from public Encroachment. Terraces
are also useful to accommodate grade changes in the
topography.

B. Entries
Terraces may be accessed from the building or directly
from the adjacent sidewalk.

C. Dimensions

1. The front of Terrace may be at a maximum two
feet behind the property line.

2. Terraces may be elevated up to four feet above
the adjacent sidewalk.

3. Where the Height of Terrace requires a rail or
wall that Height shall not exceed the minimum
Height established by the Building Code.

4. Terraces shall be at least seven feet deep and
Setback 20-25 feet.

D. Paving and Landscaping

1. Setback Area fronting Raised Residential
Terrace shall be landscaped.

2. Raised Terraces may include paving and/or
landscape.

E. Furnishing Zone
The raised Terrace may be furnished.

F. Additional Standards
None.
7’ Min.
4’ Max.

Terrace Front
Terrace Front
Sidewalk
7’ Min.
2’ Max.
2’ Max.

Property Line
Property Line
Setback Area
20’-25’
13’ Min.

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 64 FRONTAGE TYPES • URBAN FRONTAGE
Figure 4-24 - Urban Frontage Illustrative Section
An urban Frontage Type for residential or commercial
ground-floor uses.

Figure 4-23- Urban Frontage Conceptual Plan
Figure 4-22 - Urban Frontage Illustrative Photo

4.10 Urban Frontage
A. Intent Statement
An urban Frontage is suitable for residential lobbies
or commercial/office uses. It may provide access to
ground- floor uses, but is primarily characterized by
windows facing the sidewalk. Unlike storefronts, there
is no minimum ground floor Height. Nor is there a
requirement for individual entries to individual shops, offices or other spaces that constitute the Frontage.

B. Entries

1. Urban Frontages shall provide primary
pedestrian access directly from the sidewalk
to a lobby and need not provide entrances to
individual shops or spaces like a Shopfront.

2. Primary pedestrian access shall be visually
emphasized through the use of canopies,
awnings or fixed overhead architectural
Projections such as porticos.

C. Dimensions

1. Urban Frontages shall be set at grade or may
be elevated up to 12 inches above the adjacent
sidewalk.

2. Building Faces shall be set back from the curb a
minimum of 15 feet and a maximum of 25 feet.

D. Paving and Landscaping

1. Urban Frontages are characterized by
Hardscape and/or landscape within the Setback
area.

E. Furnishing Zone
Where permitted, outdoor seating may be provided
in front Setbacks. Low growing landscape is also
permitted to provide privacy for activities taking place in building’s ground-floor space.

F. Additional Standards
None.

Residential Lobby or
Office/Commercial Uses
Sidewalk
15’-25’
Property Line
Setback Area
Property Line

Page 435 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 5 SITE AND

OPEN SPACE

STANDARDS

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 66 SITE AND OPEN SPACE STANDARDS • STANDARDS AND GUIDELINES

SITE AND OPEN SPACE

STANDARDS

5.1 Purpose and Intent
The architectural standards in this section apply to all multifamily residential and mixed-use developments in Diamond Bar. They address the composition of buildings as well as functional aspects of building, parking, and outdoor space design. The goal of this section is to ensure that development is consistent with the goal of creating a human-scale mixed-use environment in which each individual building furthers the overall vision.

The images in this section are for Illustrative purposes, only provided to illustrate intent.

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67 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development SITE AND OPEN SPACE STANDARDS • GRADING STANDARDS

5.2 Grading Standards

5.2.1 Applicability
The Standards of this section shall apply to mixeduse parcels only. They address the setting of ground floor elevations to ensure accessibility and a seamless Connection between the streets and spaces of the plan
area, and the ground floor of commercial offerings.

5.2.2 Standards
The finished floor elevations of buildings, shall be set in accordance with the following criteria:

1. The finished floor elevation of primary building
entrances and storefront entrances shall be set to
meet existing (as designed) street grade. This may
require the stepping of the building floor plate.

2.Cross and longitudinal slopes of up to five percent
are allowed in any front Setback areas subject to
ADA access requirements, however, areas abutting
storefront Frontages shall not exceed two percent.

3.Notwithstanding 5.2.2.1 and 5.2.2.2 above, the
following grading strategies may also be employed,
where necessary:
• The cross slope of the tree zone may be
increased to a maximum of five percent.
• Sidewalk cross slope may be decreased to a
minimum one percent provided that adequate
drainage is demonstrated.
• The longitudinal slope of the public sidewalk
may be increased to exceed that of the adjacent
public street by a maximum of three percent.
• The Terrace Frontage may be utilized (See
Figure 5-1 and Section 4.9).

4.In order to ensure that transitions between
sidewalks and storefronts are as seamless as
possible, steps, ramps, and retaining walls solely
associated with building ingress and egress are
prohibited in the Front Yard except where it is
required for grading purposes. In such cases a
Terrace Frontage shall be utilized (See Section 4.9).

Figure 5-1 - Illustrative Photo of Terrace Frontage

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 68 SITE AND OPEN SPACE STANDARDS • EXTERIOR LIGHTING & OUTDOOR SEATING AREAS, CAFES, AND RESTAURANTS IN MIXED-USE ZONES

5.3 Outdoor Seating Areas, Cafes, and
Restaurants in Mixed-Use Zones
Outdoor seating areas, cafes and restaurants in mixeduse zones shall be in conformance with DBCC Section

22.42.080(3).

Notwithstanding the statement above, the following
standards are also applicable:

1. Outdoor seating areas, cafes, and restaurants
on private property, as part of mixed-use
development shall not interfere with pedestrian
flow and circulation along adjacent sidewalks,
from public ways to building entries, or with
amenities, such as bicycle racks and benches.

5.4 Outdoor Furnishings Visible from
ROWs Applicable to Mixed-Use Zones

1. The following materials shall be used for
furnishings in private spaces that are visible
from public ROWs.
a. Benches, chairs and tables shall be made
of be made of wood, metal, stone, concrete,
recycled High-Density Polyethylene (HDPE),
or a composite of wood and plastic (recycled
HDPE) composite.
b. Trash cans and bike racks shall be made of
metal.
c. Planters and pots shall be made of metal,
stone, terra cotta, cast stone, cast concrete,
hand-sculpted concrete, or composite
material that resemble wood.
d. Moveable furnishings such as tables and
chairs shall not be stored in a location that
is visible from the street.

Figure 5-2 - Illustrative Photo showing outdoor seating areas, cafes and restaurants in mixed use conditions
Figure 5-3 - Illustrative Photo showing street furnishings in mixed-use conditions

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69 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Figure 5-4A - Two Tiers of Planting Figure 5-4B - Three Tiers of Planting

5.5 Landscape Standards
Landscape design standards, including standards for
street trees and parkways, shall be in conformance
with DBCC Chapters 22.24, 22.26 and Section

21.30.070.

Notwithstanding the statement above, the following
standards are also applicable in all areas covered by
these Objective Design Standards.

1. Street tree spacing shall be between twenty-five
and forty-five feet (30’-0” and 50’-0”) on center
with adjustments in spacing pursuant to Public
Works Department standards.

2. Plants shall be arranged with the tallest shrubs
located at base of buildings and structures,
transitioning to lower shrubs adjacent to
sidewalks and curbs. A minimum of two Heights
or tiers shall be provided (e.g., low planting and
taller planting adjacent to the wall). (See Figure
5-4A for dimensions of each tier)

3. For landscape areas greater than ten feet wide,
provide a minimum of three tier levels (e.g.,
groundcover or annuals, low planting and tall
planting adjacent to the wall). (See Figure 5-4B
for dimensions of each tier)
Tall Tier: 3’-0” to 4’-0” High
Foundation and Flowering Shrubs
Tall Tier: 3’-0” to 4’-0” High
Foundation and Flowering Shrubs
Low Tier: 1’-6” to 2’-6” High
Perennials and Groundcover
Mid-Level Tier: 2’-0” to 2’-8” High
Flowering and Annual Shrubs
Low Tier: 1’-6” to 2’-6” High
Perennials and Groundcover
Parkway: Less than 24” High
Foot traffic tolerant
Low Perennials and Groundcover
Parkway: Less than 24” High
Foot traffic tolerant
Low Perennials and Groundcover
SITE AND OPEN SPACE STANDARDS • LANDSCAPE STANDARDS

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 70 SITE AND OPEN SPACE STANDARDS • COMMON OPEN SPACE & INTERIOR COURTYARDS

5.6 Common Open Space
Common Open Space standards shall be in
conformance with DBCC Sections 21.30.070, 22.26.040
and 22.26.050.

Notwithstanding the statement above, the following
standards is also applicable in all areas covered by
these Objective Design Standards.

1. Artificial trees, shrubs, turf and plants shall not
be used as landscape within the public right of
way, any parking area, or within an open space
area directly visible to from the public right of
way.

2. Outdoor dining areas shall have concrete
to match the adjacent sidewalk, or special
pavers, and/or a row of Planters or bollards, or
permeable fence to delineate the dining space.

3. Benches, chairs and tables shall be made
of be made of wood, metal, stone, concrete,
recycled High-Density Polyethylene (HDPE), or a
composite of wood and plastic (recycled HDPE)
composite.

4. Planters and pots shall be made of metal, stone,
terra cotta, cast stone, cast concrete, handsculpted concrete, or composite material that resemble wood.

Figure 5-5 - Common Open Space Illustrative Photo
Outdoor dining area divided from public walking space with railings.

5.7 Interior Courtyards
Required outdoor space may be accommodated in
interior courtyards located on the ground plain or on a Podium, as allowed by the relevant Building Type (see
Chapter 2).

When provided, interior courtyards shall adhere to the
following standards:

1. Shade Trees. Interior courtyard landscaping
shall include shade trees or shading devices.

At least one 3-inch caliper specimen tree is
required per 1,000 square feet of courtyard
area.

2. Dimensions. Minimum courtyard dimension
on any side shall be 30 feet (exclusive of
Encroachments) unless indicated otherwise in
the Building Types.

3. Blank Walls. Where courtyards are visible from
the Principal Frontage, Blank Walls shall not be
permitted inside the perimeter of the courtyard.

Alternatively, courtyards shall include windows,
doors, balconies and/or shall be screened with
landscape, such that the landscape covers at
least 2/3 of the Blank Wall.

Figure 5-6 - Interior Courtyard Illustrative Photo
Landscape and Hardscape create intimate spaces in this
courtyard.

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71 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development SITE AND OPEN SPACE STANDARDS • FENCES, HEDGES AND WALLS & RETAINING WALLS Figure 5-7 - Hedge Screening Service Area
A hedge and other plantings effectively screens a service area from view.

5.9 Retaining Walls
Retaining wall standards shall be in conformance with
DBCC Chapter 22.20, except that unfinished concrete
block and interlocking concrete pavers (such as
keystone) shall not be used as retaining walls when
visible from the street.

5.8 Fences, Hedges and Walls
Garden walls, retaining walls, hedges and fences may
be used to define the edge between adjoining private
properties. Fences, hedges and walls facing the public
street shall also comply with the Frontage Type
standards (see Chapter 4).

Fences, hedges and walls standards shall be in
conformance with DBCC Chapter 22.20.

Notwithstanding the statement above, the following
standards are also applicable in all areas covered by
these Objective Design Standards.

1. Location. Garden walls, retaining walls, hedges
and fences shall be built at least 18 inches from
the property line, to allow room for footings and
planting.

2. At Storefronts. Walls and fences shall not
be used at storefronts or storefront cafés,
except that retaining walls shall be permitted
in situations where they are necessary to
accommodate grade changes.

3. Plastic and Vinyl. No plastic or vinyl fencing
shall be permitted forward of the Build-to Line,
unless the material is a recycled plastic lumber
(RPL).

4. Vegetation utilized as hedges adjacent to public
sidewalks or paseos shall not be of the type that
produces thorns or spines (e.g., blackberries,
rose bushes, or cacti, among others).

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 72 SITE AND OPEN SPACE STANDARDS • VEHICULAR PARKING, LOADING AREAS & BICYCLE PARKING STANDARDS

5.11 Loading Areas
Loading areas shall be in conformance with DBCC
Section 22.30.100.

Notwithstanding the statement above, the following
standards are also applicable in mixed-use projects.

1. Service and loading areas shall be located
away from public streets whenever possible.

Entrances to loading areas shall be no more
than 18 feet wide.

2. Entrances to loading areas fronting public
streets shall be enclosed by an opaque gate
covering the entire entrance. Chain link fencing
is not permitted for use as a gate.

3. Loading areas must accommodate both trash
and recycling.

4. Multifamily residential projects over 100 units
shall designate space for moving truck loading
and unloading.

5.12 Bicycle Parking Standards
Bicycle parking standards shall be in conformance with
DBCC Section 22.30.90.

Notwithstanding the statement above, the following
standards for short-term bicycle parking are applicable in mixed-use projects.

Short-term bicycle parking is intended to offer a
convenient and accessible area to park bicycles for
customers and other visitors.

1. 10% of the multifamily bicycle parking shall be
short-term that is, for building visitors who will
use the space for two hours or less.

2. 90% of hotel bicycle parking shall be shortterm.

3. 90% of eating and drinking establishments
bicycle parking shall be short-term.

4. 80% of office and retail business bicycle
parking shall be short-term.

5.10 Vehicular Parking
Vehicular parking standards shall be in conformance
with DBCC Chapter 22.30.

5.10.1 Parking Location

1. Parking location shall be in conformance with
the requirements of the particular Building Type
to which is associated. (See Chapter 2)

2. At Block Fronts facing public streets, at-grade
or above-ground parking that may be provided
shall be screened by a habitable space no less
than 20 feet deep. Subterranean parking may
extend to the property line.

5.10.2 Parking Access

1. To the extent parking is provided, it shall be
accessed from a public or private alley when
present. If no alley is present, parking access
shall be from the street consistent with DBCC
Section 22.30.080.

2. Pedestrian entrances to all parking shall
be directly from the street, except that
underground parking garages may be entered
directly from a building.

5.10.3 Parking Structures

1. All parking structure exits shall maintain a
Clear Sight Triangle pursuant to Public Works
Department standards to protect pedestrians
from exiting vehicles. The triangle is placed with
one point aligned with the driver’s position. The
opposite far edge of the triangle is then placed
flush with the edge of the pedestrian pathway.

2. Pedestrian crossing signage shall be placed
at all garage structure exits along with a stop
bar set back from the edge of the pedestrian
pathway.

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73 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Figure 5-8 - Service and Auxiliary Equipment Illustrative Photo
Trash enclosures and utilities shall be screened from view.

5.13 Service and Auxiliary Equipment
Service and auxiliary equipment standards shall be
in conformance with DBCC Sections 22.16.080 and

22.16.100.

1. Service, utility, and mechanical functions,
including retail loading, shall be located in alleys
whenever present. When alleys are not present,
service, utility and mechanical functions shall
be placed behind buildings and provisions for
access shall be made.

2. Service, utility, and mechanical equipment that
is visible from the street shall be screened from
view with landscaping or enclosures. Backflow
preventers and fire standpipes, along with utility
box transformers shall be screened.

3. All screening devices shall be of the same
materials and colors of the building to
which they are attached. Operable gates
and decorative trim may differ in color and
materiality.

4. Trash areas that are visible from public streets
or adjacent properties shall be enclosed by
walls. Trash area entrances shall be enclosed by
a door.

5. Roof vent penetrations and mechanical
equipment shall be located at least ten feet (10’-
0”) from any exterior Building Face.

5.14 Exterior Lighting
Exterior Lighting shall be in conformance with DBCC
Section 22.16.050 or the applicable Specific Plan.

SITE AND OPEN SPACE STANDARDS • SERVICE AND AUXILIARY EQUIPMENT & EXTERIOR LIGHTING

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 74 Page Left Intentionally Blank

Page 445 of 618 ends

ARCHITECTURAL
STYLES
Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 6

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 76 ARCHITECTURAL STYLES • INTENT

ARCHITECTURAL STYLES

6.1 Intent
An architectural stylistic framework shall be the basis for establishing Objective Design Standards for all multifamily and mixed-use development. This framework honors the San Gabriel Valley’s existing Architectural Styles by providing a regulatory framework to continue its eclectic architectural tradition.

The following standards enable the significant characteristics of the following five Architectural Styles that have been identified as relevant. The five styles are identified below:
• Main Street Commercial
• Spanish Revival
• Craftsman
• Art Deco
• California Contemporary
The above styles are described in terms that assist the user of these standards to understand their historic precedence and prepare contemporary designs in these historic styles. Each style is described and differentiated from the others through nine criteria. These describe their prevalent language of composition, technique, materiality, and detail for the user to apply to new designs: massing, base, primary walls of upper floors, roof- wall transitions, roof, drainage, door and window openings, attached elements.

Applicants for multifamily residential and mixed-use development (that includes housing) shall select and conform to one Architectural Style and one corresponding Building Type for each proposed building pursuant to the standards. If a development is proposing several buildings and/or Building Types, the applicant may provide different Architectural Style and Building Type combinations in the same development. Each style is described and differentiated from the others through nine building criteria as follows:

1. Applicability

2. Massing

3. Base and Ground Floor

4. Primary Walls of Upper Floors

5. Roof Wall Transitions

6. Roof

7. Drainage

8. Door and Window Opening

9. Attached Elements

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77 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development ARCHITECTURAL STYLES • MAIN STREET COMMERCIAL

6.2 Main Street Commercial
The Main Street Commercial style is derived from the late nineteenth and early twentieth century mixed-use architecture that characterized the downtowns of small cities and towns throughout California. Buildings of this style are decorated rectangular masonry (or stucco) boxes in form and are typically mixed-use with commercial ground floors in terms of function.

However, this style may also be used for buildings that are exclusively residential.

Multi-Story Façades are typically divided into base, middle and top, or “tri-partite”, with the ground floor taller than the shorter upper floor which is finished by a significant Parapet. The ground floor has expansive glass interrupted by structural columns with transoms to allow light to penetrate deep into the interior.

Upper-level windows are typically punched openings, often grouped in twos or threes by piers, pilasters, or other Façade elements, creating a repetitive bay structure directly relating to the ground floor openings.

A. Applicability

1. This style is applicable to mixed-use zones only.

Figure 6-1 - Main Street Commercial Illustrative Photo
Figure 6-2 - Main Street Commercial Illustrative Photo

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 78 Figure 6-3 - Rectangular Form
Percentage Diagram
Figure 6-4 - Large Windows
Ground Floor
Figure 6-5 - Decorative Brick
Figure 6-7 - Cornice
Figure 6-6 - Single Plane
Figure 6-8 - Parapet and Cornice
ARCHITECTURAL STYLES • MAIN STREET COMMERCIAL
B. Massing

1. Main Street Commercial buldings shall
present Frontages that are square or simple
rectangles and as a single Volume.

2. Notwithstanding this requirement, no
greater than 10 percent of the total Frontage
may include deviations to the rectangular
forms, through changes in Height, Setback
or Encroachment, or corner articulation. See
Figure 6-3.

C. Base and Ground Floor

1. An explicit base level element shall ground the
building up to two feet six inches maximum
Height, such as a bulkhead, footer, or sill.

2.The ground floor base shall provide a
minimum of one-foot-wide horizontal band of
a different plane on the Façade at the top of
the first Story, such as a Cornice or lintel.

3. Exterior wall materials shall be applied as a
horizontal band of brick, stone, cast concrete,
stucco, terra cotta, or cementitious fiberboard.

D. Primary Walls of Upper Floors

1. Upper floor walls shall be expressed as
single-plane expanse of cast concrete
brick, stucco and plaster materials, terra
cotta or cementitious fiberboard siding.

Notwithstanding that, nothing in this
statement shall be interpreted as prohibiting
the inclusion of Decorative Detail on the
surface or that is additive in nature.

2.Where present, attached building wall
elements, such as awnings and balconies, shall
encroach into the building’s Setbacks.

3. Window shutters shall not be allowed.

E. Roof-Wall Transitions

1. Exterior walls shall transition directly into roof
Parapets or into plaster molding or Cornice
line forms.

2.For buildings with flat roofs, exterior Parapets
shall be articulated as a continuation of the
exterior wall and shall include a Cornice
or Decorative Detail on the surface of the
Parapet.

A
A
B ≤ 10%(A+A)
B

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79 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development ARCHITECTURAL STYLES • MAIN STREET COMMERCIAL
F. Roof

1. For buildings with pitched roofs greater than 6:12,
roofs shall overhang the wall surfaces by a minimum
of two feet.

G. Drainage

1. Where a rain drainage catchment is visible, (i.e.,
not embedded within the building’s walls) it shall
be conducted with a combination of gutters and
downspouts fabricated either from untreated copper
or painted metal to contrast with the Building Face.

H. Door and Window Openings

1. Ground floor Fenestration shall conform with the
requirements for the appropriate Frontage (see
Chapter 4).

2.Transoms above doorways are required on the
ground floor.

3.Upper floor windows and doors shall have a square
or vertically oriented rectangular shape. This
requirement does not preclude the use of arches or
articulated lintels atop the openings.

4.Door and window openings shall be centered on the
spaces between the pattern of ground floor columns
and piers.

5.Windows on upper floors shall appear to be
“punched” by recessing them from the surface
by a minimum of two inches. Where windows are
arranged in groups of two or three, the entire group
shall be recessed from the outer surface.

6.Door and window openings on the Upper Floors of
Primary Frontages shall constitute a minimum of
33 percent of the Façade. This requirement may be
reduced to 20 percent if windows and doors are
recessed at least four inches from the surface of the
Façade.

7. Windows on the upper floors shall be double-hung or
awning type.

I. Attached Elements

1. Awnings, canopies, and upper floor balconies or bay
windows are subject to Encroachment requirements,
See DBCC Section 22.16.090 (3) and Section 3.8 of
this document.

Figure 6-9 - Awnings at Commercial Frontage
Figure 6-10 - Canopy Frontage
Figure 6-11 - Roof with Detailed Parapet

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 80 ARCHITECTURAL STYLES • MAIN STREET COMMERCIAL
Roof and Eaves
Flat roof with Parapet or projecting
molding and Cornice lines.

Awnings
Extend into the public right-of-way.

If Setback, shall refer to Section

22.16.090(3) of DBCC.

Windows
Upper floor windows align with
ground floor windows, doors, and
piers or column patterns.

Shopfront
Transoms and piers articulate
doors and windows.

Base
Shopfront base grounded with a sill or a footer.

Cornice or Lintel
The ground floor base shall provide a horizontal
band of a different plane on the Façade at the
top of the first Story.

Walls
Flat planes of brick, stone, cast
concrete, stucco, and plaster
materials.

Figure 6-12 - Main Street Commercial Elements Diagram (Ground Floor Commercial)

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81 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Roof and Eaves
Flat roof with Parapet or projecting
molding and Cornice lines.

Awnings
Extend into the public right-of-way.

If Setback, shall refer to Section

22.16.090(3) of DBCC.

Windows
Upper floor windows align with
ground floor windows, doors, and
piers or column patterns.

Base
Residential entrance with a Stoop
Cornice or Lintel
The ground floor base shall provide a horizontal
band of a different plane on the Façade at the
top of the first Story.

Walls
Flat planes of brick, stone, cast
concrete, stucco, and plaster
materials.

ARCHITECTURAL STYLES • MAIN STREET COMMERCIAL
Figure 6-13 - Main Street Commercial Elements Diagram (Ground Floor Residential)

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 82 Page Left Intentionally Blank

Page 453 of 618 ends

83 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development ARCHITECTURAL STYLES • SPANISH REVIVAL

6.3 Spanish Revival
Spanish Revival architecture draws from the adobe structures of the California Missions, which were prominently showcased in the California Pavilion at the 1893 World’s Columbian Exposition. The style was subsequently adopted by several railroad companies for train stations and hotels, and it soon became a defining architectural language across California, used extensively in both institutional and residential settings.

The style is characterized by thick-walled massing, often expressed through deeply recessed openings and arcades.

Emulating this depth—particularly in features such as arcades— is essential to achieving an authentic expression of the style.

Spanish Revival, including the Mission subtype, represents a mature and complex architectural tradition that evokes a strong sense of urban character and an intimate relationship with the natural environment.

Key features include white or light-colored stucco walls, sloped red clay tile roofs with exposed rafter tails, shaped Parapets, and generous balconies—often detailed with ornamental metal railings. Façade Compositions may be either symmetrical or asymmetrical, but window sizes, locations, and alignments are typically varied. Arched openings are common, appearing unframed in upper-Story windows or as part of ground-floor arcades at entries or along Frontages facing Public Spaces.

Figure 6-14 - Spanish Revival Illustrative Photo
Figure 6-15 - Spanish Revival Illustrative Photo

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 84 A. Applicability

1. This style is applicable to all mixed-use and
multifamily zones.

B. Massing

1. Volumetric composition shall be with a
primary Volume accounting for at least 60
percent of the Frontage, but no more than 90
percent offset by a variety of lesser Volumes
See Figure 6-16.

C. Base and Ground Floor

1. While not required, if an articulated base
element is applied on the Ground Plane, such
as a footer, it shall be no taller than three feet
maximum Height from grade.

2.Where utilized, the base element shall be one
of the following:
a.A horizontal band painted with the darkest
accent color applied to the building Façade.
b.A horizontal band painted the exact same
color as the entire building Façade.
c. A horizontal band of ceramic tile, plaster,
stone or cast concrete materials
D. Primary Walls of Upper Floors

1. Primary Upper floor walls of the primary
Volume shall be expressed as a single-plane
expanse of stucco or plaster surface, smooth
or hand-troweled textures. Primary Walls of
secondary Volumes shall be surfaced in stucco
or plaster.

2.Notwithstanding the requirement above,
materials such as decorative tile, ornamental
metal, stone, or terra cotta may recess within
the wall, set flush with the surface of the
wall or in the case of traditional moldings,
be applied atop the surface. Stone or cast
concrete materials shall not be allowed above
the ground floor base element, except for
attached chimneys, unless the material is a
continuation of the identical material used
below.

E. Roof-Wall Transitions

1. Where a Parapet is used at the roofline, it
shall include at least one of the following
elements to establish a visible termination of
the wall plane:

ARCHITECTURAL STYLES • SPANISH REVIVAL
Figure 6-16 - Volumetric
Composition Diagram
Figure 6-18 - Single Plane
Composition
Figure 6-20 - Parapet with Flat
Roof
Figure 6-17 - Painted Base with
Recess
Figure 6-19 - Balcony
Overextending Sidewalk
Figure 6-21 - Clay Tile with No
Eave
A
A≥ 60%(A+B) ≤ 90%(A+B)
B

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85 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development a. A shaped or stepped Parapet profile (e.g.,
curvilinear, sloped, or crenellated).
b.A coping element with a contrasting material,
texture, or Projection of at least two inches from
the wall surface.
c. A plaster molding, Cornice band, or cap that
projects a minimum of two inches and extends
continuously along the Parapet edge.

Flat, unadorned Parapets without variation in form
or detailing are prohibited. All Parapet profiles
shall be consistent with historical Spanish revival
precedents, such as Mission-shaped curves.

2.Exterior walls shall transition into roof form by one of three devices:
a. A projected wooden Eave with exposed wooden
rafters;
b. Plaster molding; or
c. A tile cap.

3.Foam moldings are permitted only on the second
(2nd) floor or above and shall not be used in
occupied or high-use areas such as doorway trim or
facing balconies.

F. Roof

1. Gabled or hipped roofs shall be low-pitched at a 3:12 minimum to 5:12 maximum ratio and finished in clay
or concrete barrel or S-tile.

2.Flat roofs are allowed and shall be articulated as
an explicit exterior surface (tile may be multi-color
randomly placed) visual transition to the sky. May be
accessible and used as balconies or Terraces.

3.Overhanging downslope Eaves shall be a minimum
of 16 inches wide supported by wooden rafter tails
and exposed Eaves or metal brackets.

G. Drainage

1. Rain drainage catchment shall be conducted with
a combination of half-round gutters and round
downspouts entirely in dark painted metal or
untreated copper and shall be located within six
inches of building corners.

H. Door and Window Openings

1. Window on Primary Façades shall be punched
openings with no surround and deep-set with a
minimum two-inch plaster return.

2.Window and opening compositions shall only utilize
the following shapes:
• Square;
• Vertically proportioned rectangles (Height greater
than width);
• Arched top forms, including full, segmental, or
eyebrow arches;
• Circular or oval;
• Quatrefoil, trefoil, or other symmetrical
ornamental forms, each not exceeding 36 inches
in width, and used only as accent openings.

Horizontally proportioned openings (width greater
than Height) are prohibited, except when used as
small vents or decorative accents not exceeding 24
inches in width.

3.Shutters shall be the aggregate size of the
associated opening.

4.Operable windows on upper floor shall be casement
or single hung.

5.Sliding doors are not permitted unless they have a
minimum stile width of four inches.

6.Ground floor Fenestration shall conform with the
requirements for Shopfronts. (See Section 4.3).

7. Upper floor windows and doors shall be
geometrically square or rectilinear oriented
with the longer dimension running vertically.

Notwithstanding this, nothing in this requirement
shall preclude the use of arches or articulated lintels atop the openings.

8.Door and window openings shall be centered on the
spaces between the pattern of ground floor columns
and piers.

9.Doors and Windows openings on upper floors shall
appear to be “punched” by recessing them from the
surface by a minimum of two inches. Where windows
are arranged in groups of two or three, the entire
group shall be recessed from the outer surface.

10.Door and window openings in the Upper Floors of
Primary Frontages shall constitute a minimun of
33 percent of the Façade. This requirement may be
reduced to 20 percent if the windows and doors are
recessed a minimum of four inches.

I. Attached Elements

1. Awnings, canopies, and upper floor balconies or bay
windows are subject to Encroachment requirements.
(See DBCC Section 22.16.090(3) and Section 3.8 of
this document.)

2.Balconies shall be supported by bracketing entirely
in metal or exposed wood.

3.Bay windows shall be supported in wooden brackets
or exposed joist extensions.

ARCHITECTURAL STYLES • SPANISH REVIVAL

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 86 ARCHITECTURAL STYLES • SPANISH REVIVAL
Shallow Eaves
Overhanging downslope
Eaves supported by
wooden rafter tails and
exposed Eaves or metal
brackets.

Base
Articulated footer is
optional.

Flat or Low Pitch Roofs
If a pitched roof, gables with barrel tile and exposed Eaves and hipped with exposed Eaves. If a flat Parapet, the exterior wall transitions to the sky.

Vertical Architectural Elements
Include chimney, belvedere, covered patio and Terrace.

Balconies
Supported by metal brackets.

Windows
Recessed square or
rectangle shape.

Walls
A single-plane of stucco
or plaster.

Figure 6-22 - Spanish Revival Elements Diagram

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87 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development ARCHITECTURAL STYLES • CRAFTSMAN

6.4 Craftsman
The English Arts and Crafts movement of the mid- to late-19th century inspired the Craftsman architecture of California. It was invented as a style of the handmade and earthy, a reaction to the repetitiveness and homogenization of the industrial culture emerging at the time. The Arts and Crafts movement became the expression of choice for an unadorned, popular, and natural architecture. Good examples of Craftsman buildings for larger scaled three to five Story buildings can be found in historical hotels, California courtyard multifamily housing and mountain / national park resorts.

In its most simple form, it is a wood box surrounded by various attached elements, such as roof dormers or expressive
downspouts. Walls are typically horizontally placed wood siding, shingles, or board-and-batten (often in a combination of two or three) with a foundation base and piers in stone, brick or stucco.

A large gable shallow sloped roof with dormers to break up massing is typical. Dormers may feature shed or flat roofs and can have gable ends. Rafter tails, decorative brackets, and porch columns are exposed, smooth, woodwork. Windows and doors are vertical in proportion, trimmed in wood. Roofs are clad in wood or shingles with broad overhangs and Eaves.

A. Applicability

1. This style is applicable to all mixed-use and multifamily zones.

Figure 6-23 - Craftsman Illustrative Photo
Figure 6-24 - Craftsman Illustrative Photo

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 88 B. Massing

1. Volumetric composition shall be with a
primary Volume accounting for at least 60%
of the Frontage, but no more than 90% offset
by a variety of lesser Volumes.

2.At least 70 percent of the top floor shall
be subsumed in the roof with dormers.

In buildings with varying Heights, this
requirement shall apply to the top floor in
each section of the building.

3.Dormers may have shed or flat roofs, or gable
ends.

C. Base and Ground Floor

1. An explicit base element shall be applied at
the Ground Plane, and it shall be measured up
to one to three feet in Height and expressed
as horizontal band/Layer pattern and made of
brick, stone, stucco, or shingle materials.

2.Ground floor shall be differentiated in terms of
materials and/or color from upper floors.

3.Piers shall be a minimum of 6”x6” if wood
posts, and 18”x18” if stone or stucco.

D. Primary Walls of Upper Floors

1. Masonry materials, such as brick, stone or
stucco shall not be allowed above the ground
floor base element, except for attached
chimneys.

2.Upper floor exterior walls shall be clad
primarily (up to 90 percent of a vertical
Façade section) as single-plane expanse of
wood, shingle, shake, or clapboard siding up
to the roof line. with a secondary material
utilized from 10-30 percent of any vertical
section). Secondary materials can be defined
by a change in color, a change in size or
pattern of the shingles or shakes, or a
completely different material.

3.The space between columns and piers shall
be either square or vertically rectangle shape
with a Height to width proportion ratio of no
more than 3:1. See Figure 6-29.

4.Door and window openings shall be centered
on the spaces between columns/piers below.

5.Piers shall be a minimum of 6”x6” if wood
posts.

ARCHITECTURAL STYLES • CRAFTSMAN

ADD NEW PHOTO

ADD NEW PHOTO
Figure 6-25 - Masonry and Stone
Base
Figure 6-27 - Paired Openings
Composed Horizontally
Figure 6-30 - Craftsman
Illustrative Photo
Figure 6-26 - Gutter and
Downspout
Figure 6-28 - Painted Shingles
Over Siding
Figure 6-29 - Space Between
Columns and Piers

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89 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development E. Roof-Wall Transitions

1. Exterior walls shall transition into roof form by
projected wooden Eaves with exposed rafters.

2.Eaves shall have an overhang of at least three feet.

F. Roof

1. Roofs shall be designed with a pitched gable or
hipped roof. Principal gables are between 3:12 and
6:12, and shed slopes shall be less than the principal
slope (between 2:12 and 4:12).

2.Eaves shall be supported by wood bracket details
and exposed wood rafters to support gable end
roofs.

3.Dormers, if used, shall have shed or gable ends.

G. Drainage

1. Rain drainage catchment shall be conducted with a
combination of gutters and downspouts in entirely
painted metal or untreated copper finishes.

H. Door and Window Openings

1. Window lites may be divided into equal increments
or be divided on a portion of a window (such as
the upper portion of a double-hung or casement
window).

2.Primary entry doors on the ground floor shall
be made of wood or fiberglass that are made to
resemble wood.

3.Window and opening compositions shall be either
square and/or vertically rectangle shaped. However
up to three windows may be grouped to form a
horizontal opening.

4.One Specialty Window (neither square nor
rectilinear) per vertical section, may be utilized.

5.Window shutters, if used, shall match the aggregate
size and shape of the associated opening.

6.Door and window openings on the Upper Floors of
Primary Frontages shall constitute a minimum of 25
percent of the Façade.

I. Attached Elements

1. Porches, chimneys, and trellises can encroach
beyond the primary exterior surface of buildings and
into their Setbacks. See DBCC Section 22.16.090(3).

2.Balconies and bay windows shall be supported by
wood brackets, or tapered or square posts.

ARCHITECTURAL STYLES • CRAFTSMAN
Figure 6-31 - Craftsman Illustrative Photo
Figure 6-32 - Bracketing of a Roof Gable

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 90 ARCHITECTURAL STYLES • CRAFTSMAN
Eaves
Overhangs with rafter tails,
exposed Eaves, and metal brackets.

Base of the Building
Footer element and ground floor
shall be brick, stone, stucco or
shingle materials.

Piers
Piers are a minimum of 6”x6” if
wood posts.

Roof and Eaves
Low pitched roof, 3:12 min - 5:12 max
ratio, with gables facing primary street
or side street.

Dormers
Proportioned and detailed as scaled
down versions of the building.

Change in Materials
Ground floor brick, stone, or
stucco materials change to
shingle or clapboard siding on
upper floors.

Windows
Vertical or square shapes.

Balcony
Wooden upper floor
balconies provide usable
outdoor space.

Figure 6-33 - Craftsman Elements Diagram

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91 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development ARCHITECTURAL STYLES • ART DECO

6.5 Art Deco
Art Deco emerged in the US in the 1920s and 30s, and was the first widely popular modern style, spreading through large cities and small towns alike. The style made a major impact on commercial, institutional, and large-scale residential buildings throughout California. The Art Deco style is characterized by Volumes that step back at upper floors, long pilasters that run the entire Height of the building, flat roofs, smooth lines, geometric shapes, and streamlined forms. Windows typically are located between the pilasters and, between floors, are often separated by decorated transom panels. Although towers may have roofs clad in metal, the overall emphasis remains on verticality and geometric ornamentation.

Decorative features, such as infill panels, entry doors or canopies, incorporate strong geometric motifs, sometimes inspired by pre-Columbian architecture, and are often made of contrasting materials, such as metal or ceramic tile. The more exuberant versions of the style incorporate aggressive geometries of chevrons or ziggurats in Façade design, while a more streamlined version, sometimes referred to as Arte Moderne, utilizes more sedate compositions with a horizontal emphasis.

A. Applicability

1. This style is applicable to all mixed-use and multifamily zones.

Figure 6-34 - Art Deco Illustrative Photo
Figure 6-35 - Art Deco Illustrative Photo

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 92 B. Massing

1. Building Façade sections shall have either
dominant vertical decorative or functional
elements such as grouping of windows, piers
or decorative band or horizontal decorative or
functional elements, but not both within the
section of the Façade.

2.Where tower elements are utilized, they shall
rise above the roof Cornice.

C. Base and Ground Floor

1. Ground floor exterior walls shall be supported
on a base composed of stone, cast concrete,
brick, glazed terra cotta tile, stucco, or glazed
ceramic tile (bathroom tile is not permitted).

2.The entire ground floor Height may be
articulated as the base of the building.

D. Primary Walls of Upper Floors

1. A Primary Façade Plane shall account for
50-80 percent of the Upper Floor Façade.

For the purposes of this calculation, windows
and doors, which sit within two inches from
the surface of the Façade is calculated as
part of the Primary Façade Plane. At least 10
percent of the Façade shall sit on at least one
additional Façade Plane (a secondary plane)
projected out from or recessed in from the
Primary Façade Plane by a minimum of one
foot. Balcony rails may be included as part of
the secondary Façade Plane. There is no limit
to the number of Façade Planes provided that
the Primary Façade Plane occupies at least 60
percent of the total Façade.

2.Where pilasters running the entire Height
of the building are utilized, the combined
surface of the outer edge of the pilasters may
be included as part of the secondary Façade
Plane.

3.Façades shall be composed of stucco,
fiberboard, brick, or tile, however, included
in those materials shall be both polished and
matte finishes on separate elements, ensuring
that each finish covers at least 15 percent of
the design’s total surface area.

4.Materials shall be used to create vertical or
horizontal elements (but not both) through
exaggerated piers or horizontal bands.

5.At least one geometric inlay using contrasting
materials shall be utilized in each Façade
section.

ARCHITECTURAL STYLES • ART DECO
Figure 6-36 - Art Deco Illustrative
Photo
Figure 6-38 - Art Deco
Illustrative Photo
Figure 6-40 - Extensions with
Metal Panels
Figure 6-37- Ground Floor as Base
Figure 6-39 - Art Deco Illustrative
Photo
Figure 6-41 - Undulating Parapet

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93 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development E. Roof-Wall Transitions

1. Exterior walls shall extend beyond the roof level and form a Parapet that is configured in one of three
ways:
a.Pilasters that continue beyond Height of
interstitial walls,
b.Walls that continue beyond Height of the pilasters,
c. Wall and pilaster that reach to same Height.

2.Nothing in the requirement above shall preclude the
use of Cornice lines, or the use of contrasting metal
tile, or other inlaid materials as part of Parapet.

F. Roof

1. Roofs shall be flat with the exterior walls extending beyond the roofline to form Parapet walls.

G. Drainage

1. Roof drainage shall be located within walls of
the building itself and therefore not visible on
the Façade except that external scuppers and
downspouts may be utilized on rear Façades.

H. Door and Window Openings

1. Individual windows shall be multi-paned, with
a transom window above the main window.

Alternatively, Glass Block is permitted as a window
type.

2. Under each window, either as a sill or spandrel shall be a decorative area of at least one-foot in Height.

This can be made of a contrasting material to the
Façades primary surface, or the primary surface but
installed in a contrasting pattern.

3. Windows shall have vertical dimensions that are at
least 1.5 times the width. Notwithstanding the above
requirement, up to three windows may be grouped
together within a larger frame.

4. Windows shall not cut into the pilasters.

5. Door and window openings on the Upper Floors of
Primary Frontages shall constitue a minimum of 25
percent of the Façade.

6. Windows on upper floors shall appear to be
“punched” by recessing them from the surface
by a minimum of two inches. Where windows are
arranged in groups of two or three, the entire group
shall be recessed from the outer surface.

I. Attached Elements

1. For the ground floor of mixed-use buildings, a
projecting canopy constructed of metal, fiberglass
and/or glass of at least three feet in depth shall be
provided over retail storefronts.

2.Awnings, canopies, and upper floor balconies or bay
windows are subject to Encroachment requirements.

See DBCC Section 22.16.090(3) and Section 3.8 of
this document.

3.Projecting balconies must project at least three feet beyond the primary Building Face.

4.Balcony railings shall be constructed of metal, and
must include a geometric pattern, covering no less
than 50 percent of the total railing area. These could
include geometric shapes, chevrons, zigzags or
repeating linear elements.

ARCHITECTURAL STYLES • ART DECO
Figure 6-42 - Stepped-Back Volumes
Figure 6-43 - Art Deco Illustrative Photo

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 94 ARCHITECTURAL STYLES • ART DECO
Windows
Under each window,
either as a sill or spandrel
shall be a decorative area
of at least one-foot in
Height.

Base
The entire ground floor
Height may be articulated as
the base of the building.

Roofs
Roofs shall be flat with the
exterior walls extending
beyond the roofline to form
Parapet walls.

Windows
Individual windows shall be
multi-paned, with a transom
window above the main
window.

Walls
Materials shall be used to
give vertical or horizontal
emphasis (but not both)
through exaggerated piers or
horizontal bands.

Figure 6-44 - Art Deco Elements Diagram (Ground Floor Commercial)

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95 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Windows
Under each window,
either as a sill or spandrel
shall be a decorative area
of at least one-foot in
Height.

Base
The entire ground floor
Height may be articulated as
the base of the building.

Roofs
Roofs shall be flat with the
exterior walls extending
beyond the roofline to form
Parapet walls.

Windows
Individual windows shall be
multi-paned, with a transom
window above the main
window.

Walls
Materials shall be used to
give vertical or horizontal
emphasis (but not both)
through exaggerated piers or
horizontal bands.

ARCHITECTURAL STYLES • ART DECO
Figure 6-45 - Art Deco Elements Diagram (Ground Floor Residential)

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 96 Page Left Intentionally Blank

Page 467 of 618 ends

97 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development ARCHITECTURAL STYLES • CALIFORNIA CONTEMPORARY

6.6 California Contemporary
The California Contemporary style refers to the streamlined Modernism that flourished in the middle of the last century in Southern California and throughout the country. Influenced by the climate and products of industrial design, the style featured flat roofs, asymmetrical and streamlined building composition, repetitive building elements articulated as abstract planes or forms, and expanses of glass that allow integration between interior and exterior spaces. The use of industrial materials such as glass, concrete and fiberglass in combination with natural materials is common.

Given its abstract nature, the California Contemporary style relies heavily on the use of a “parti” or a set of major decisions about the overall organization of the building mass as a formative element. The process for buildings in this style shall begin with the parti, which shall include the following specific formal elements: an asymmetric composition with a horizontal emphasis balanced with vertical feature(s); a subdivision of the overall building form into discrete and distinguishable masses; the articulation of the exterior surface into planes with a visible Layering of elements, and expanses of glass. Unique Façade features may be highlighted with a bright or contrasting color.

Despite its use of an abstract vocabulary, buildings shall be articulated with a human scale. A base and middle shall be established; a cap or attic Story may be clearly articulated or implied through modest upper level adjustments such as a taller Parapet.

Figure 6-46 - California Contemporary Illustrative Photo Figure 6-47 - California Contemporary Illustrative
Photo

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 98 A. Applicability

1. This style is only applicable to mixed-use
zones only.

B. Massing

1. Buildings of this style shall be composed to
create depth within the Façade itself referred
to as “Layered Massing”.
a.Layered Volumes: Buildings must include
a minimum of two Volumes with differing
Heights , materials, colors and/or widths.

These Volumes may abut one another or
appear to be “Layered” with one appearing
to overlap the other in whole or in part.

There is no maximum number of Volumes.
b.Bay System Alignment: These Volumes or
Layers shall align with a regular bay system,
which may be structural or non-structural.
c. Layered Projection: Each Volume or Layer
shall project or recess a minimum of four
inches from the adjacent plane. Maximum
depth of these Projections or recessions is
not regulated.
d.Overlapping Masses: There are two methods
for combining Volumes and Layers:
• Volumes must be physically adjacent to
other Volumes along the Façade.
• Alternatively, Layers must physically
overlap adjacent Volumes or other Layers.
e.Material Coordination: Materials and their
color and application shall follow the bay
divisions. Each bay shall use consistent
material placement, finishes, or patterns to
visually reinforce the bay system.
f. Prohibited Conditions: Façade Compositions
with non-repetitive Layering, random
massing, or components that do not meet
the above Projection, overlap, or bay
alignment requirements are not permitted.
g.The quantity of Volumes or Layers is
unregulated.

C. Base and Ground Floor

1. A base is not required for this style.

ARCHITECTURAL STYLES • CALIFORNIA CONTEMPORARY
Figure 6-48 - Example of a Base
Articulated as Glass Panels
Figure 6-50 - California
Contemporary Illustrative Photo
Figure 6-52 - Roof Articulated
with Projected Metal Overhang
Serving as a Cornice
Figure 6-49 - Example of California
Contemporary Townhouse
Figure 6-51 - Different Materials
Identify Different Façade Planes
Figure 6-53 - California
Contemporary Illustrative Photo

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99 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development D. Primary Walls of Upper Floors

1. A Primary Façade Plane shall account for 40-70
percent of the Upper Floor Façade. For the purposes
of this calculation, windows and doors, which sit
within two inches from the surface of the Façade are
calculated as part of the Primary Façade Plane. At
least 30 percent of the Façade shall sit on at least
one additional Façade Plane (a secondary plane)
projected out from or recessed in from the Primary
Façade Plane by a minimum of two feet. Balcony
rails may be included as part of the secondary
Façade Plane. There is no limit to the number of
Façade Planes provided that the Primary Façade
Plane occupies at least 40 percent of the total
Façade.

2.Façade Planes are expressed as expanses of wood,
cementitious, or metal siding, plaster or stucco,
metal panels, or cast concrete. These various
materials may be used in conjunction with one
another, for example to identify different Façade
Planes.

3.For buildings or portions of buildings which are four or more Stories in Height, it is necessary to provide
articulation for the top Story of the building. This
may be accomplished by a color change, material
change, the extension of a Primary Façade Plane
from behind a secondary plane, and/or a Cornice/
Belt Course at the bottom of the uppermost Story.

Other techniques may be approved by the Director
on an individual basis.

E. Roof-Wall Transitions

1. The building cap is where the side of the building
meets the top. It shall incorporate the roof Parapet
or roofline.

2.Parapet of flat-roofed Volumes may be articulated
as an extension of the wall below or as a distinct
railing.

F. Roof

1. Roofs may be sloped, barrel shaped, flat, or a
combination thereof. Sloped roofs shall be clad in
metal or tile.

G. Drainage

1. Gutters visible to the primary Façade are prohibited.

2.Where downspouts and scuppers are visible on the
primary Façade, they shall be made of painted metal
or copper in rectangular or circular form.

H. Door and Window Openings

1. Primary doorways shall be located asymmetrically
from the center of the building.

2.Windows and Doors on flat surfaces shall be
recessed at least two inches to create a shadow line
or have a projecting surround or a projecting rain
screen assembly of at least four inches beyond the
window to create a shadow. The exception to this
is where Glass Block is used as a window type. As
such cases, the Glass Block may be flushed with the
surrounding exterior surface.

3.Door and window openings on the Upper Floors of
Primary Frontages shall constitute a minimum of 33
percent of the Façade.

I. Attached Elements

1. A minimum of 10 percent of all windows and doors
facing a Primary Façade shall have horizontally
oriented, metal sun shades supported by metal
brackets extending at least 18 inches from the outer
face of the window or door. This requirement is
waived where the windows are recessed at least four
inches from the outer wall (or rain screen). Attached
Balconies may substitute for the attached sun
shades.

2.Awnings, canopies, and upper floor balconies or bay
windows are subject to Encroachment requirements.

See DBCC Section 22.16.090(3) and Section 3.8 of
this document.

3.Projecting balconies shall project at least three feet beyond the primary Building Face.

4.Balcony railings shall be constructed of perforated
metal or laminated glass. If the ground floor of
mixed-use buildings is projecting forward from
the floors above, a projecting canopy of at least
three feet in depth shall be provided over retail
storefronts. Projecting canopies are not required,
where the ground floor is recessed from the floors
above.

ARCHITECTURAL STYLES • CALIFORNIA CONTEMPORARY
Figure 6-54 - California Contemporary Illustrative Photo

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 100 ARCHITECTURAL STYLES • CALIFORNIA CONTEMPORARY
Attached Elements
Awnings, canopies, and
upper floor balconies
or bay windows are
subject to Encroachment
requirements.

Base
Shall be articulated as
distinct from Upper
Floors, for commercial
uses.

Windows
Windows and Doors on
flat surfaces must be
recessed at least two
inches to create a shadow
line or have a projecting
surround or a projecting
rain screen assembly
of at least four inches
beyond the window to
create a shadow.

Roof Wall Connections
Building caps shall
facilitate roof forms
that are integral to the
building’s design on all
sides of the structure.

Walls
Façade Planes are
expressed as expanses
of wood, cementitious, or
metal siding, plaster or
stucco, metal panels, or
cast concrete.

Figure 6-55 - California Contemporary Elements Diagram (Ground Floor Commercial)

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101 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Attached Elements
Awnings, canopies, and
upper floor balconies
or bay windows are
subject to Encroachment
requirements.

Roof Wall Connections
Building caps shall
facilitate roof forms
that are integral to the
building’s design on all
sides of the structure.

Walls
Façade Planes are
expressed as expanses
of wood, cementitious, or
metal siding, plaster or
stucco, metal panels, or
cast concrete.

Figure 6-56 - California Contemporary Elements Diagram (Ground Floor Residential) ARCHITECTURAL STYLES • CALIFORNIA CONTEMPORARY

Page 472 of 618 ends

Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 102 Page Left Intentionally Blank

Page 473 of 618 ends

GLOSSARY OF
TERMS
Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 7

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 104

GLOSSARY OF TERMS
This chapter provides definitions of terms and phrases used in this Objective Design Standards that are technical or that may not reflect common usage, and is intended to supplement the Development Code Definitions found in Chapter 22.80 of the Diamond Bar City Code (Development Code). If a definition in this section conflicts with a definition found in the Development Code, these definitions shall control for the purposes of new developments. If a word or phrase used in this Objective Design Standards is not defined in this section, or in the Development Code, the Director shall make a determination, giving deference to common usage and the context in which the term or phrase is used.

GLOSSARY OF TERMS

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105 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development

GLOSSARY OF TERMS
A
Access Point
A point of entry on a Block Front providing access to
parking or service facility areas.

Apparent Building
A portion of a building designed to appear as distinct
from the rest of the building, and with its own
entrance.

Architectural Features
Building elements that are not strictly integral to the building’s massing, Fenestration or Frontage condition, but are added to serve a decorative or functional
purpose. They include elevator overruns, stair towers,
Shade Structures like pergolas or awnings, Cornices,
cupolas, projecting friezes or grills, photovoltaic
panels, attached sculpture or other artwork, clock
towers, turrets and the like. Occupiable spaces other
than elevator overruns, stair towers or mechanical
equipment spaces are not considered Architectural
Features.

Architectural Style
The characteristic form and detail of buildings from a
particular historical period or school of architecture.

B
Belt Course
A horizontal band or row of masonry, tile, or other
decorative material, including paint set into or
attached to a wall, and forming part of an exterior
architectural composition. Set in line with window sills it helps to make the horizontal line of the sills visually more prominent. Set between the floors of a house, it
helps to make the separate floors distinguishable from
the exterior of the building.

Block
An area bounded by streets on all sides used
to regulate the land uses, Heights, and design
requirements in the Objective Design Standards.

Block Front
The plane of the edge of each side of a Block or
section of a Block facing a public or private right-ofway or Public Space.

Block Length
The length of a parcel or series of parcels measuring
from the edge of one public right-of-way to another
or from the edge of one public right-of-way to the
opposite end of the parcel should it adjoin a private
parcel edge.

Build-to Line
A line, parallel to the property line, that must be
occupied by a specified percentage of the building
Façade. The Build-to Line is measured as a distance
from the property line. For example, a five-foot Buildto Line would be located five feet from the property line within the parcel.

Building Face
The exterior wall of a building.

Building Frontage
See DBCC Section 22.80.020.

Building Type
A structure category defined by its massing, entry
location, disposition on the lot, and configuration,
including Frontage and Height. It is occasionally
defined by its function as well. There are eleven
Building Types permitted: Townhouse, Flex/Loft,
Small Multi-Family, Six/Eight Packs, Walk-Up, Carriage
House, Courtyard, Small Mixed-Use, Urban Block, Wrap
Building and Mixed-Use Big Box.

C
Clear Sight Triangle
An area near the exit of a driveway or parking
structure that must remain free of visual
obstructions—such as walls, landscaping, or signage—
to ensure that drivers can clearly see approaching
pedestrians and vehicles before entering a public
walkway or street.

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 106

GLOSSARY OF TERMS
Dooryard
Dooryard fronts are located in front Setbacks and
provide small landscaped and paved yards at building
entrances. They are often enclosed by low walls,
fences, or hedges.

Driveway
A paved vehicular access way that provides a direct
Connection between a public or private street and onsite parking areas, garages, or carports. A Driveway shall be located on private property and shall not be
used for parking unless otherwise specified. Driveways
may be shared by multiple units or buildings where
permitted.

E
Eave
The edge of the roof which overhangs the face of a
wall and, normally projects beyond the building. The
Eave forms an overhang to divert water clear of the
walls and, in some cases, provides shade.

Encroachment
Any structural element (including Architectural
Features) that extends from the Building Face
into the public right-of-way or Setback. Permitted
Encroachments are provided in Section 3.8.

F
Façade
A Building Face that is along a Frontage.

Façade Composition
The expression of a Façade through a variety of
techniques such as patterns, fenestration, materials,
texture, or finishes. Façade Composition is used to
create the architectural character and design theme of
a building.

Façade Plane
Any stretch of a building Façade existing along the
same axis line, regardless of pattern differentiation or change in rhythm.

Common Open Space
Outdoor open spaces that are shared and accessible
only to building residents and their visitors which
may include courtyards, gardens, play areas, outdoor
dining areas, recreational amenities, and rooftop open
spaces.

Conceptual
Examples depict one possible design that would
substantially conform to the Standards, but are not
determinative.

Connection
A space that links one physical space to another.

It may be traversable by pedestrian, bicycle or
automobile traffic.

Cornice
Any horizontal molded decorative Projection that
crowns a building, i.e. at the meeting of the roof and
wall. A Projecting Cornice on a building may have the
function of diverting rainwater free of its walls, but it purpose is primarily decorative.

Courtyard Building
A Building Type defined in Section 3.10.

D
Decorative Detail
An intricate design or embellishment that enhances
the aesthetic appeal of a structure. Decorative Details can encompass ornamentation, moldings, and patterns
that enrich the style of a building.

Density
See DBCC Section 22.80.020
Development Code
Title 22 of the Diamond Bar City Code (DBCC), the
municipal code of the City of Diamond Bar, California.

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107 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development It measures the intensity of light hitting a surface,
not the light emitted by a source (that’s measured in
lumens).
• Example: If a lamp provides 100 lumens of light
evenly distributed over an area of 100 square feet,
the illumination on that surface is one footcandle.

Footprint
Footprint or building Footprint provides the outline
of a building drawn along the exterior walls, with a
description of the exact size, shape, and location of its foundation.

Forecourt
A Frontage Type as defined in Section 4.8.

Frontage
See Building Frontage, DBCC Section 22.80.020.

Frontage Occupancy
The minimum percentage of the Block Front that must
contain a building. Frontage Occupancy requirements
shall apply to the first three floors of a building.

Frontage Type
As defined in Chapter 4.

Front Yard
See DBCC Section 22.80.020.

Furnishing Zone
A multi-purpose area that serves as a buffer between
the pedestrian travel way and the vehicular travel
way and parking on the street. It provides space for
sidewalk appurtenances such as street trees, planting
strips, street furniture, public art, sidewalk café
seating, sign poles, temporary signage, signal and
electrical cabinets, fire hydrants, bicycle racks and bus shelters.

Façade String
A series of Townhouses or Flex/Loft units attached
together in a single building.

Façade Width
The horizontal distance along a street or public way of a single building Façade.

Faux Stone Appearance
A simulated stone veneer that appears artificial
either because of visible seams in the veneer panels,
uniformity in shape, size, and coloration, repetitive
patterns, and/or a uniform edge.

Fenestration
The arrangement and design of windows and other
openings on a building’s Façade.

Flex/Loft Building
A Building Type defined in Section 2.5.

Floor Area Ratio (FAR)
See DBCC Section 22.80.020. For projects subject to
these Objective Design Standards, the following shall
be excluded from the total Floor Area:
• Garages: provided they are screened by habitable
space of at least 20-feet in depth along all Public or
Private Streets;
• Loading areas, and Trash enclosures;
• Elevator shafts, except that one floor shall be
included as part of the floor area; and
• Transformer enclosures.

Footcandle
A footcandle is a unit of measurement for illumination, or how much light falls on a surface. One footcandle
equals one lumen per square foot. In other words:
• 1 footcandle = 1 lumen / 1 square foot

GLOSSARY OF TERMS

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 108 G
Glass Block
A hollow translucent Block usually with ribbed exterior made by fusing two sections of clear pressed glass
at high temperature and used as a building material
chiefly for wall panels.

Gross Lot Area
See Lot Area, DBCC Section 22.80.020.

Ground Plane
A horizontal plane of reference from which vertical
measurements can be taken. Unless otherwise
specified, the ground plan refers to the adjacent grade at the sidewalk.

H
Habitable Encroaching Space
The portion of the building enclosed by walls and a
roof that projects beyond the Building Face along the
ground floor.

Habitable Projecting Space
The portion of the building enclosed by walls and a
roof that projects beyond the Building Face and is
raised a minimum of nine feet from the sidewalk, such
as bay windows.

Habitable Space
Space in a structure that is occupiable and is used
primarily for living, sleeping, eating, selling of goods, or cooking. Bathrooms, closets, halls, storage areas
and utility spaces are not considered habitable spaces.

Hardscape
Non-living elements of landscaping that primarily
consist of paving materials such as brick, stone, wood, and concrete.

Height
See DBCC Section 22.16.060 (Height measurement
and Height limit exceptions).

Horizontal Plane Break
See Figure 2-1.

I
Illustrative
Examples that illustrate one possible design that
would substantially conform to the Standards but are
not determinative.

L
Landscaped Area
See DBCC Section 22.80.020.

Layer
As part of a Façade Composition, a Layer is a Volume
that appears to overlap a recessed portion of the
Façade.

Layered Massing
See Section 6.6.B.

Layered Volumes
Where multiple Volumes appear to abut or overlap one
another.

Living Areas
Rooms designated as living room, family room, den,
study, library and/or kitchen, rather than sleeping and service rooms.

Lot Area, Gross
See Lot Area, DBCC Section 22.80.020

GLOSSARY OF TERMS

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109 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Parapet
A barrier that is an upward extension of a wall at the
edge of a roof, Terrace, balcony or walkway. Where
extending above a roof, a Parapet may simply be the
portion of an exterior wall that continues above the
edge line of the roof surface, or may be a continuation of a vertical feature beneath the roof. They are
primarily used as guard rails or to conceal rooftop
equipment.

Paseo
A public place or path designed for walking;
promenade that connects into or through a
development.

Plane Break
The area of the building where the plane of the Façade
varies in depth. Plane Breaks can be horizontal or
vertical.

Planter
An above grade container for planting.

Plaza
A type of Public Space that is enclosed by Building
Frontages on all sides, and will reclaim Public Space
for pedestrian use from otherwise predominantly
vehicular intersections.

Podium
The lower floors of a building that form the “base”
of a building typically including a courtyard level
above. Podiums typically include structured parking, a
courtyard level above, a different and larger floorplate than floors above, and may be a different construction
type than the rest of the building.

M
Minimum Frontage Occupancy
(Also, Minimum Building Frontage Occupancy) is
the minimum percentage of a Block Front at which
a Building Frontage is set either at or within twelve
inches of the Build-to Line or within the minimum
and maximum Setback lines, as required by the Block
development standards.

Mixed-Use Big Box
A higher Density Building Type defined in Section 2.13.

N
Non-Habitable Encroaching Space
The portion of the building that extends beyond the
Building Face along the ground floor, which is not
enclosed by walls and a roof, such as a Stoop.

Non-Habitable Projecting Space
The portion of the building that extends beyond the
Building Face, which is not enclosed by walls and a roof and raised a minimum of nine feet from the ground
floor, such as a balcony.

Non-Habitable Space
The portion of a building which is not enclosed by
walls and a roof, such as a Stoop, balcony, or roof deck.

O
Objective Design Standards
Objective Design Standards are defined in California
Government Code sections 65913.4 and 66300(a)(7)
as standards that involve no personal or subjective
judgment by a public official and are uniformly
verifiable by reference to an external and uniform
benchmark or criterion available and knowable by
both the development applicant or proponent and the
public official before submittal.

GLOSSARY OF TERMS
Figure 7-1 - Isometric View of a Podium

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Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development 110 Public Space
Public outdoor space reserved for active and passive
recreation.

R
Roadway
The area in the right-of-way as measured from
curbface to curbface intended for vehicular travel, as
well as bicycle travel, in designated areas.

S
Setback
See DBCC Section 22.80.020
Shade Structure
A roofed or partially roofed structure that provides
shade. It can be freestanding or fixed to a building.

The roof material may be composed of fabric and be
removable, or temporary and made of plants or vines.

Alternatively, the roof may be fixed or permanent.

Sidewalk Grade
A level plane along the top of the sidewalk pavement.

Sign
See DBCC Section 22.80.020.

Six/Eight Pack
A Building Type defined in Section 2.6.

Special Paving
Includes any hard surface flooring material except
non-tinted poured-in-place concrete and asphalt that
can be used in outdoor flooring applications, Special
Paving can include, saw-cut concrete, concrete pavers,
tinted and/or stamped concrete, brick, stone, porcelain and/or ceramic, provided such materials are approved
by the Diamond Bar Public Works Department.

Podium Level
The level directly above the Podium. The Podium Level
typically includes a courtyard, a smaller building area than the levels below, and a change in construction
type.

Predominant Building Height
The Height at which at least 50% of a building is
measured.

Primary Entrance
The main point of access for pedestrians into a
building.

Primary Façade Plane
Majority area of the Façade that is in the same plane.

Principal Frontage
The Frontage designated to bear the addresses of
and Primary Entrances to the individual units of a
Townhouse or Flex/Loft Building, or other building.

Private Open Space
Outdoor open space areas that are intended for
private use for each dwelling unit and may include
balconies (covered or uncovered), private gardens,
private yards, Terraces, decks and porches, etc.

Projecting Cornice
A horizontal decorative molding that crowns a
building, and extends beyond the Building Face.

Projection
An architectural element or portion of the building
that extends beyond the Building Face into the public
right-of-way or Setback that is raised a minimum of
nine feet from the sidewalk or open space.

Public Realm
Composed of public rights of way and private Front
Yards, the Public Realm is the communal social setting
of urban life. The term Public Realm is not intended to provide general public with any legal access rights to
private property.

GLOSSARY OF TERMS

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111 Diamond Bar Objective Design Standards for Multifamily & Mixed-Use Development Urban Block
A medium Density Building Type defined in Section

2.12. Urban Frontage
A Frontage Type as defined in Section 4.10.

V
Vertical Plane Break
See Figure 2-1.

Volume
As part of a Façade Composition, a Volume is a
Projection or recession of building mass, as part of
Layered Massing technique.

W
Walk-Up Building
A Building Type defined in Section 2.7.

Water Feature
A design element where open water performs an
aesthetic or recreational function such as a fountain.

Water Table
A projecting course or molding on the lower exterior
wall of a building designed to deflect rainwater away
from the foundation.

Wrap Building
A medium Density Building Type defined in Section

2.11. Z
Zoning District
See DBCC Section 22.80.020.

Zoning Ordinance
See DBCC.

Specialty Window
Any window that comes in a non-traditional shape or
configuration, such as a circle, oval, arch, or triangle, i.e., not typically found in standard rectangular
windows. Specialty Windows can be fixed or operable.

Stoop
A Frontage Type as defined in Section 4.5.

Shopfront
A Frontage Type as defined in Section 4.3.

Story
Any level part of a building with a floor that could be used by people (for living, work, storage, recreation,
etc.), excluding levels of the building that are not
covered by a roof such as the Terrace on the rooftops
of many buildings.

Street, Public or Private
See Street, DBCC Section 22.80.020.

Subdivision
See DBCC Section 22.80.020.

Swale
A low or slightly depressed natural area for drainage.

T
Terrace, Commercial and Residential
A Frontage Type as defined in Sections 4.4 and 4.9.

Thin Veneer
A lightweight Layer of stone or brick veneer that
appears to be less than 1.5 inches thick.

Townhouse
A Building Type defined in Section 2.3
U

GLOSSARY OF TERMS

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GLOSSARY OF TERMS
DIAMOND BAR California

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Addendum No. 2 to the
Diamond Bar Comprehensive General Plan Update
and Climate Action Plan
Environmental Impact Report
State Clearinghouse No. 2018051066
Prepared for:

City of Diamond Bar
21810 Copley Drive
Diamond Bar, CA 91765
Prepared by:

Sapphos Environmental, Inc.
430 North Halstead Street
Pasadena, California 91107
February 2026

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TABLE OF CONTENTS

SECTION PAGE

1.0. INTRODUCTION AND OVERVIEW ............................................................................... 1

1.1 PURPOSE ........................................................................................................... 1

1.2 ADDENDUM ORGANIZATION ............................................................................ 3

1.3 ADDENDUM SCOPE OF ENVIRONMENTAL REVIEW ....................................... 4

1.4 ADOPTION AND AVAILABILITY OF ADDENDUM .............................................. 5

2.0. PROJECT DESCRIPTION ............................................................................................. 6

2.1 BACKGROUND ................................................................................................... 6

2.2 PROJECT LOCATION ......................................................................................... 6

2.4 PROPOSED PROJECT ..................................................................................... 12

2.5 APPLICABILITY OF ODS .................................................................................. 13

2.6 GOALS AND OBJECTIVES ............................................................................... 13

2.7 DISCRETIONARY APPROVALS ....................................................................... 15

2.8 CONSTRUCTION .............................................................................................. 15

3.0. ENVIRONMENTAL ANALYSIS .....................................................................................16

3.1 AESTHETICS .................................................................................................... 17

3.2 AIR QUALITY .................................................................................................... 20

3.3 BIOLOGICAL RESOURCES .............................................................................. 25

3.4 CULTURAL RESOURCES ................................................................................ 30

3.5 ENERGY ........................................................................................................... 33

3.6 GEOLOGY, SOILS, AND SEISMICITY .............................................................. 36

3.7 GREENHOUSE GAS EMISSIONS .................................................................... 41

3.8 HAZARDS AND HAZARDOUS MATERIALS ..................................................... 44

3.9 HYDROLOGY AND WATER QUALITY .............................................................. 50

3.10 LAND USE AND HOUSING ............................................................................... 56

3.11 NOISE ............................................................................................................... 60

3.12 PUBLIC FACILITIES AND RECREATION ......................................................... 63

3.13 TRANSPORTATION .......................................................................................... 68

3.14 TRIBAL CULTURAL RESOURCES ................................................................... 72

3.15 UTILITIES AND SERVICE SYSTEMS ............................................................... 74

3.16 WILDFIRE.......................................................................................................... 77

4.0. LIST OF PREPARERS ..................................................................................................81

4.1 LEAD AGENCY ................................................................................................. 81

4.2 CONSULTANT .................................................................................................. 81

5.0. REFERENCES ..............................................................................................................82

TABLE PAGE
1 Step-by-Step Application of ODS ................................................................................... 14 2 2021-2029 Regional Housing Needs Assessment ......................................................... 56

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FIGURE PAGE
1 Project Location ............................................................................................................... 8 2 Regional Vicinity .............................................................................................................. 9 3 Topographic Quadrangle ............................................................................................... 10 4 City Land Use Distribution ............................................................................................. 11

APPENDICES
A Diamond Bar Objective Design Standards for Multifamily and Mixed-Use Development B Mitigation Monitoring and Reporting Program

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1.0. INTRODUCTION AND OVERVIEW
This Addendum No. 2 to the Diamond Bar General Plan 2040 and Climate Action Plan Environmental Impact Report (State Clearinghouse No. 2018051066) (hereafter, Certified EIR)1 is prepared pursuant to and in compliance with Section 15164 of the California Environmental Quality Act (CEQA) Guidelines for minor refinements to the Diamond Bar General Plan 2040 (General Plan 2040)2 being undertaken by the City of Diamond Bar (City). The City adopted the General Plan Update and Climate Action Plan in 2019. The potential environmental impacts of the General Plan 2040 and Climate Action Plan were analyzed in the Certified EIR.

In 2022, the City adopted the 2021-2029 Housing Element Update.3 The City concurrently amended the General Plan 2040 Land Use and Economic Development Element. The potential impacts of the 2021-2029 Housing Element Update and concurrent Land Use and Economic Development Element amendment were determined to be within the scope of the Certified EIR.

The City concluded that neither a subsequent nor a supplemental EIR was required. Accordingly, the City adopted Addendum No. 1 to the Certified EIR on August 11, 2022.

Addendum No. 2 describes the proposed Diamond Bar Objective Design Standards for Multifamily and Mixed-Use Development (hereafter, proposed project). The proposed project sets minimum design standards for multifamily and mixed-use development throughout the City to be used during the development review process, with the intent that all new multifamily and mixeduse developments be required to adhere to the proposed project (Appendix A, Diamond Bar Objective Design Standards for Multifamily and Mixed-Use Development). The General Plan 2040 established standards related to development density for all land uses with the City, including multifamily residential and mixed-use development. As described in the Diamond Bar Objective Design Standards for Multifamily and Mixed-Use Development, the proposed project would further establish objective design standards that would dictate the bulk, mass, and design of multifamily residential and mixed-use development, further refining the General Plan 2040 standards. The Diamond Bar Objective Design Standards for Multifamily and Mixed-Use Development have been developed consistent with the General Plan 2040 and 2021-2029 Housing Element Update, and, as such, remains within the scope of the Certified EIR.

1.1 PURPOSE
The purpose of Addendum No. 2 to the Certified EIR is to document technical changes and additions to the project description. The analysis evaluates whether in-depth, further environmental review is required such as a subsequent or supplemental EIR (Public Resources Code § 21166; CEQA Guidelines § 15162). The State CEQA Guidelines Appendix G checklist for Initial Study was modified for use in the addendum analysis. Instead of asking whether the project would have “potentially significant” impacts, the checklist questions were modified consistent with the State CEQA Guidelines on subsequent environmental review to ask whether the proposed project would result in a substantial change in the project requiring major revisions to the prior EIR, or a substantial change in circumstances requiring major revisions to the EIR, or new 1 City of Diamond Bar. 2019. Diamond Bar Comprehensive General Plan Update and Climate Action Plan Draft Environmental Impact Report. https://ceqanet.opr.ca.gov/2018051066/2 2 City of Diamond Bar. 2019. Diamond Bar General Plan 2040. https://www.diamondbarca.gov/961/General-Plan2040 3 City of Diamond Bar. 2022. Diamond Bar General Plan 2040 Housing Element Update 2021-2029.

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information showing new significant impacts or a substantial increase in the severity of previously identified significant impacts (Public Resources Code § 21166; CEQA Guidelines § 15162).

An addendum to the EIR is appropriate when changes to a project would require minor modifications to the previous EIR and would not entail new significant environmental effects or a substantial increase in the severity of previously identified significant effects. In accordance with State CEQA Guidelines Section 15164, this addendum to the Certified EIR incorporates, by reference, the analysis contained Certified EIR and addresses only the new issues specific to the proposed project as described in this document.

Section 15164 of the State CEQA Guidelines provides the following guidance regarding the preparation of an addendum to an EIR:
(a) The lead agency or responsible agency shall prepare an addendum to a previously certified EIR if some changes or additions are necessary but none of the conditions described in Section 15162 calling for preparation of a subsequent EIR have occurred. (b) An addendum to an adopted negative declaration may be prepared if only minor technical changes or additions are necessary or none of the conditions described in Section 15162 calling for the preparation of a subsequent EIR or negative declaration have occurred.
(c) An addendum need not be circulated for public review but can be included in or attached to the final EIR or adopted negative declaration. (d) The decision making body shall consider the addendum with the final EIR or adopted negative declaration prior to making a decision on the project. (e) A brief explanation of the decision not to prepare a subsequent EIR pursuant to Section 15162 should be included in an addendum to an EIR, the lead agency’s findings on the project, or elsewhere in the record. The explanation must be supported by substantial evidence.

Regarding Section 15164(e) of the State CEQA Guidelines, a subsequent EIR is not required pursuant to Section 15162 of the State CEQA Guidelines because none of the following circumstances have occurred with respect to the proposed project:
(1) Substantial changes are proposed in the project which will require major revisions of the previous EIR or negative declaration due to the involvement of new significant environmental effects or a substantial increase in the severity of previously identified significant effects;
(2) Substantial changes occur with respect to the circumstances under which the project is undertaken which will require major revisions of the previous EIR or Negative Declaration due to the involvement of new significant environmental effects or a substantial increase in the severity of previously identified significant effects; or (3) New information of substantial importance, which was not known and could not have been known with the exercise of reasonable diligence at the time the previous EIR was certified as complete or the Negative Declaration was adopted, shows any of the following:

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(A) The project will have one or more significant effects not discussed in the previous EIR or negative declaration;
(B) Significant effects previously examined will be substantially more severe than shown in the previous EIR;
(C) Mitigation measures or alternatives previously found not to be feasible would in fact be feasible, and would substantially reduce one or more significant effects of the project, but the project proponents decline to adopt the mitigation measure or alternative; or
(D) Mitigation measures or alternatives which are considerably different from those analyzed in the previous EIR would substantially reduce one or more significant effects on the environment, but the project proponents decline to adopt the mitigation measure or alternative.

1.1.1 Summary of Findings
As demonstrated in the initial study below, implementation of the proposed project would not require major revisions to the Certified EIR because the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts analyzed in the Certified EIR. In addition, the information throughout this addendum affirms that there is no new information of substantial importance that was previously unknown and is now available. Therefore, a subsequent EIR would not be required pursuant to Section 15162 of the State CEQA Guidelines. The City has thus determined an addendum to the previously Certified EIR to be the appropriate environmental compliance document for the proposed project. Addendum No. 2 to the Certified EIR has been prepared for the Lead Agency as defined in Section 15367 of the CEQA Guidelines.

Lead Agency Contact Information
City of Diamond Bar
Greg Gubman
Planning Division
21810 Copley Drive
Diamond Bar, CA 91765

1.2 ADDENDUM ORGANIZATION
This document is organized as follows pursuant to the requirements of the State CEQA Guidelines:
 Section 1.0, Introduction, describes the background of the proposed project; explains the rationale for preparing an addendum to the EIR as the appropriate form of environmental review pursuant to CEQA; and explains the purpose, scope, and content of the addendum to the EIR.
 Section 2.0, Project Description, describes the location, details, and objectives of the proposed project.
 Section 3.0, Environmental Analysis, evaluates whether the proposed refinements to the proposed project would result in new or substantially more adverse significant environmental impacts than those disclosed in the Certified EIR.

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 Section 4.0, List of Preparers, lists the individuals involved in preparing the document.  Section 5.0, References, lists the documents and individuals consulted during preparation of this document.

1.3 ADDENDUM SCOPE OF ENVIRONMENTAL REVIEW
This document incorporates the Certified EIR by reference and evaluates whether the proposed project would result in a new significant impact or a substantial increase in the severity of previously identified significant impacts. The Certified EIR analyzed the following environmental issue areas based on the City’s initial analysis of environmental setting and baseline conditions and comments received during the Certified EIR Scoping Period:

1. Aesthetics

2. Air Quality

3. Biological Resources

4. Cultural, Historic, and Tribal Cultural Resources

5. Energy, Climate Change, and Greenhouse Gases

6. Geology, Soils, Seismicity, and Paleontology

7. Hazards, Hazardous Materials, and Wildfire

8. Hydrology and Water Quality

9. Land Use, Population, and Housing

10. Noise

11. Public Facilities and Recreation

12. Utilities and Service Systems

13. Transportation
The Notice of Preparation (NOP) for the Certified EIR was published on May 31, 2018. In 2018, Appendix G of the State CEQA Guidelines was updated to establish the issue area of Tribal Cultural Resources. In 2019, Appendix G of the State CEQA Guidelines was updated to establish the issue areas of Energy and Wildfire. This document addresses each of the environmental resource areas previously analyzed in the Certified EIR, with updates that better reflect the changes to the State CEQA Guidelines that occurred in 2018 and 2019. Specifically, the Cultural Resources, Tribal Cultural Resources, Energy, Greenhouse Gas Emissions, Hazards and Hazardous Materials, and Wildfire sections are evaluated as separate environmental topics in Section 3.0, Environmental Analysis, of this addendum. This document analyzes the following environmental issue areas using the questions established in Appendix G of the 2025 State CEQA Guidelines.

1. Aesthetics

2. Air Quality

3. Biological Resources

4. Cultural Resources

5. Energy

6. Geology, Soils, and Seismicity

7. Greenhouse Gas Emissions

8. Hazards and Hazardous Materials

9. Hydrology and Water Quality

10. Land Use and Housing

11. Noise

12. Public Facilities and Recreation

13. Transportation

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14. Tribal Cultural Resources

15. Utilities and Service Systems

16. Wildfire

1.4 ADOPTION AND AVAILABILITY OF ADDENDUM
In accordance with State CEQA Guidelines Section 15164(c), an addendum to the EIR does not need to be circulated for public review but can be included in or attached to the Certified EIR. This addendum is publicly available as part of the Certified EIR at the City of Diamond Bar Planning Division, 21810 Copley Drive, Diamond Bar, CA 91765.

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2.0. PROJECT DESCRIPTION

2.1 BACKGROUND
Under the General Plan 2040, current regulations governing development standards and guidelines by the City include the Diamond Bar City Code and Citywide Design Guidelines.

City of Diamond Bar Zoning Ordinance
The Diamond Bar Zoning Ordinance is applied to regulate the type, location, density, and scale of residential development through Title 22 (Development Code) and the Zoning Map citywide.

The Development Code aims to preserve the character and integrity of existing neighborhoods.

The Development Code and Zoning Map set forth residential development standards for each zoning district.

City of Diamond Bar Citywide Design Guidelines
The Citywide Design Guidelines was created following adoption of the 1995 General Plan and was adopted in 1998. The Design Guidelines were intended to provide design professionals, property owners, residents, staff, and decision makers with a clear and common understanding of the City’s expectations for the planning, design, and review of development proposals. The guidelines contain provisions that address citywide elements, including building siting, building design, bulk and massing, and design guidelines that provide detailed design information of, among other things, the circulation system of new developments, including parking facilities, driveways, sidewalks, and pedestrian facilities.

2.2 PROJECT LOCATION
The proposed project would apply to all new multifamily development and some new mixed-use development throughout the City, as well as to some existing multifamily and mixed-use development undergoing substantial improvements. The following General Plan 2040 land use designations allow for multifamily residential and mixed-use development: Medium Density Residential, Medium High Residential, High Density Residential, High Density Residential-30, Town Center Mixed Use, Neighborhood Mixed Use, and Transit-Oriented Mixed Use. Both existing and future development on parcels with these land use designations have the potential to be subject to the proposed project. As such, the study area for the proposed project is established as areas where the General Plan 2040 land use designations allow for multifamily residential and mixed-use development (Figure 1, Project Location).

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The City is an approximately 9,526-acre incorporated area located on the eastern edge of Los Angeles County, California, at the far eastern edge of the San Gabriel Valley, within 30 miles of the cities of Los Angeles, Riverside, and Irvine (Figure 2, Regional Vicinity). It is bound by the cities of Industry and Walnut to the north, the cities of Pomona and Chino Hills to the east, unincorporated area of Los Angeles County within Diamond Bar’s Sphere of Influence and the City of Brea to the south, and unincorporated area of Los Angeles County to the west. The western edge of the City lies at the intersection of State Route 57 (SR-57) and SR-60, with SR-57 connecting the City to Interstate 10 (I-10) 1.5 miles north and SR-60 connecting to SR-71 roughly 2 miles east. The Industry Metrolink Station is located along Diamond Bar’s northern border within the City of Industry, providing east-west transit connections to Los Angeles and Riverside. The City is on the U.S. Geological Survey (USGS) 7.5-minute series San Dimas, California, and Yorba Linda, California, topographic quadrangles (Figure 3, Topographic Quadrangle).

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FIGURE 1
Project Location

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FIGURE 2
Regional Vicinity

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FIGURE 3
Topographic Quadrangle

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2.3 EXISTING CONDITIONS
As discussed in the General Plan 2040, the City’s overall land use pattern is characterized by large swaths of single-family residential development throughout the City along with clusters of multifamily residential and non-residential land uses. Multifamily residential development tends to be located along the major thoroughfares of Diamond Bar Boulevard, Golden Springs Drive, and Brea Canyon Road, and is often collocated with non-residential uses. Residential land makes up roughly half of all land in the city limits and is the dominant land use in the City (Figure 4, City Land Use Distribution).4
4 City of Diamond Bar. 2019. Diamond Bar General Plan 2040: Chapter 2. Land Use and Economic Development. https://www.diamondbarca.gov/DocumentCenter/View/7089/2-Land-Use-Econ-Devr?bidId= (accessed September 29, 2025).

FIGURE 4
City Land Use Distribution

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2.4 PROPOSED PROJECT
The proposed project would set minimum design standards for multifamily and mixed-use development throughout the City (Appendix A) in compliance with State mandates that seek to streamline and increase housing, as well as implement Program H-8 of the City’s certified 6th Cycle (2021-2029) Housing Element. The proposed project would be used during the development review process, and all new multifamily and mixed-use developments in the City would be required to adhere to these design standards, as well as some existing multifamily and mixed-use development undergoing substantial improvements.

The proposed project would ensure consistent, transparent, and measurable review of multifamily and mixed-use development projects in accordance with California law. The proposed project is intended to streamline project approvals by providing clear verifiable objective criteria for design that do not require subjective interpretation.

In response to the housing crisis, legislation has been passed in the State of California to bolster the State’s Housing Accountability Act, including Senate Bill (SB) 35, SB 330, SB 9, SB 6, and Assembly Bill (AB) 2011. The intent of this legislation has been to stimulate and streamline housing production housing projects that meet objective design standards (ODS). Per SB 330, SB 9, and AB 2011, an “objective design standard” means a design standard that involves no personal or subjective judgment by a public official and is uniformly verifiable by reference to an external and uniform benchmark or criterion available and knowable by both the development applicant or proponent and the public official before submittal of an application.

SB 330 and SB 9 regulate a local agency’s ability to establish design standards:
 SB 330: This bill, the Housing Crisis Act of 2019, prohibits a county or city from enacting a development policy, standard, or condition that would have the effect of imposing or enforcing new design standards that are not objective. In essence, the State has limited a local jurisdiction’s ability to apply subjective design standards, whereby the City can now only rely on the application of ODS for qualifying housing projects.  SB 9: The bill authorizes a local agency to impose objective zoning standards, objective subdivision standards, and ODS, unless those standards would have the effect of physically precluding the construction of up to two units or physically precluding either of the two units from being at least 800 square feet in floor area, prohibiting the imposition of setback requirements under certain circumstances, and setting maximum setback requirements under all other circumstances.

SB 35, SB 6, and AB 2011 establish opportunities to streamline housing projects; however, the streamlining can only be used if a housing project meets the criteria of meeting ODS. These streamlining opportunities cannot be used if a local agency does not have an established set of ODS. By adopting the proposed project, the City would encourage streamlined housing production through SB 35, SB 6, and AB 2011:
 SB 35: Under existing law, every locality has a housing production goal by income level in the Regional Housing Needs Assessment (RHNA). SB 35 requires localities to report their housing production by income level in their annual housing element progress reports (APRs). The units produced are compared to the RHNA targets at the halfway point and end of each cycle. If the locality does not meet its prorated RHNA goals, then certain projects can use a streamlined approval process over the next half-cycle. In order to use

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the streamlined approval process, one of the criteria is that the development must follow all local objective zoning and design standards.
 SB 6: This bill, the Middle Class Housing Act of 2022, deems a housing development project an allowable use on a parcel that is within a zone where office, retail, or parking are a principally permitted use, if specified conditions are met, including meeting ODS.  AB 2011: This bill, the Affordable Housing and High Road Jobs Act of 2022, authorizes a development proponent to submit an application for a housing development that meets specified objective standards and affordability and site criteria, and makes the development a use by right and subject to one of two streamlined, ministerial review processes. In order to use the streamlined, ministerial review process, the development proposal must meet objective development standards.

2.5 APPLICABILITY OF ODS
The proposed project would apply to construction projects located anywhere in the City involving the development or substantial improvement of any of the following:

1. Multifamily residential projects, including duplexes, townhouses, or multifamily dwellings.

2. Mixed-use projects featuring a combination of multifamily residential and other uses.

The proposed project would apply to any substantial improvement of existing multifamily or mixeduse development where any extension, repair, reconstruction, or other improvement of a property, the cost of which equals or exceeds 50 percent of the fair market value or assessed value of a property either before the improvement started or, if the property has been damaged, before the damage occurred. Any and all additions to buildings for which these standards are applicable shall match the style and details of the main structure. Single-family homes and development with no residential component are not subject to the ODS.

The ODS are to be used during the City’s development review process. The City will review all future projects to assure adherence to the ODS.

2.6 GOALS AND OBJECTIVES
The ODS include the following six goals:
 Goal 1: Comply with state mandates to implement new ODS for eligible multifamily housing and mixed-use development projects.
 Goal 2: Ensure that appropriate ODS are in place for housing development projects eligible for streamlined ministerial review pursuant to California Government Code Section 65913.4 and other State laws.
 Goal 3: Ensure building placement and frontage along existing or proposed streets reflects the intended character.
 Goal 4: Establish architectural standards for larger buildings to mitigate overall mass and ensure visual interest from all public vantage points.
 Goal 5: Create human-scaled development that contributes to pedestrian-oriented streets and boulevards in mixed-use zoning districts.
 Goal 6: Provide design details and illustrations that are prescriptive and objective.

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The ODS include the following eight design principles:
 Principle 1: Maintain—and in some cases, elevate—architectural variety, integrity, and quality.
 Principle 2: Ensure that streets and spaces with high volumes of pedestrian traffic are comfortable, protected from the sun, and visually and physically engaging at the ground level.
 Principle 3: Create architectural variation along a block front through diversity of massing, articulation, and architectural detailing.
 Principle 4: Animate building edges on the ground floor to create an inviting public realm and pedestrian friendly environment and to support multi-modal development and mobility.  Principle 5: Orient building façades to frame the streets and other public spaces and to take advantage of natural features, such as sunset, sunrise, mountain views and the like.  Principle 6: Provide graceful transitions between larger-scale format of multifamily structures and adjacent smaller scale single-family housing.  Principle 7: Provide standards such that new buildings can sit comfortably adjacent to existing buildings of varied styles.
 Principle 8: Provide off-street parking in surface lots or garages at the rear of buildings so that parking does not dominate the built environment.

The proposed project would work in tandem with the General Plan 2040, the City Development Code (Title 22 of the Diamond Bar City Code), and other City standards related to new construction such as stormwater drainage, traffic, hillside development, and so on.

The ODS provide a step-by-step process to incorporate its standards into future multifamily and mixed-use developments in the City. Table 1, Step-by-Step Application of ODS, is a generalization of this step-by-step application process (see Appendix A for a detailed description of the application process).

TABLE 1
Step-by-Step Application of ODS
Step/Standard Summary of Standard
Chapter in ODS
(Appendix A)

1. Determine applicable building type Structure general massing and configuration 2

2. Determine applicable building
articulation standards
Building articulation and massing 3

3. Determine applicable frontage type
standards
Frontage and relationship to public realm or
street 4

4. Check compliance with site and open
space standards
Regulates functional aspects of building form
to create human-scale environment 5

5. Determine applicable architectural style
standards
Architectural style and standards 6
The proposed project has been developed to be consistent with the General Plan 2040, as amended. The General Plan 2040 contains objective standards related to development density for all land uses in the City. The standards set forth in the proposed project dictate the bulk, mass, and design of buildings in a more detailed way than the General Plan 2040. All feasible mitigation measures in the Certified EIR apply to the proposed project.

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2.7 DISCRETIONARY APPROVALS
The proposed project would require amendments to the City Development Code (Title 22 of the Diamond Bar City Code) to incorporate the ODS.

2.8 CONSTRUCTION
Any construction phases, activities, and anticipated construction equipment associated with future buildout would be the same as those described in the Certified EIR as applicable. As with the Certified EIR, any site preparation and construction would be completed in accordance with all federal, State, and City zoning codes and requirements. Future multifamily and mixed-use development or improvements would be subject to project-specific review requirements and compliance with existing regulations.

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3.0. ENVIRONMENTAL ANALYSIS
The analyses contained herein consider whether the Certified EIR analyses remain sufficient or whether the proposed project would result in a new significant impact or a substantial increase in the severity of previously identified significant impacts.

This section presents the environmental analysis for each topic addressed in the Certified EIR.

Each of the environmental resource areas previously analyzed in the Certified EIR is addressed with updates that reflect changes to the State CEQA Guidelines since the time of analysis in the Certified EIR. Specifically, the Cultural Resources, Tribal Cultural Resources, Energy, Greenhouse Gas Emissions, Hazards and Hazardous Materials, and Wildfire sections are evaluated as separate environmental topics.

The proposed project shall incorporate and implement all feasible and applicable mitigation measures contained in the Certified EIR. Specific mitigation measures relevant to a particular impact of the proposed project are cited in the same manner as in the Certified EIR and the associated Mitigation Monitoring and Reporting Program (MMRP; Appendix B).5 5 City of Diamond Bar. November 2019. Mitigation Monitoring & Reporting Program for the City Of Diamond Bar General Plan 2040 And Climate Action Plan 2040 Environmental Impact Report. SCH No. 2018051066.

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3.1 AESTHETICS
This section evaluates the effects on aesthetics from the proposed project. This Addendum relies on and incorporates by reference the project setting and regulatory setting as described in Section

3.1, Aesthetics, of the Certified EIR. Potential impacts to aesthetics from the proposed project are discussed relative to the conclusions in the Certified EIR. The Certified EIR determined that the implementation of the General Plan 2040 would result in less than significant impacts with regard to the following: the existing visual character (including the visual quality of the project site and surroundings), scenic vistas, and new source of substantial light or glare which would adversely affect day or nighttime views in the area. The Certified EIR stated that General Plan 2040 would have no impact on state scenic highways. Pursuant to State CEQA Guidelines Section 15164, this analysis determines whether the proposed project would result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to aesthetics compared to the Certified EIR.

3.1.1 Setting
The physical and regulatory environmental setting for aesthetics is the same as described in the Certified EIR. The proposed project would not alter the physical or regulatory conditions described in the Certified EIR.

3.1.2 Impact Analysis
Project Impact Analysis
The potential for the proposed project to result in a new significant impact or a substantial increase in the severity of previously identified significant impacts to aesthetics was evaluated in relation to the following questions as stated in Appendix G of the State CEQA Guidelines.

Would the project:
(a) Except as provided in Public Resources Code Section 21099, would the proposed project have a substantial adverse effect on a scenic vista?
The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to scenic vistas. The proposed project would set new minimum design standards for future multifamily and mixed-use development throughout the City (see Section 2.2). The Certified EIR determined that the General Plan 2040 would continue to regulate development in open spaces, local hillsides and ridges, and distant views of the San Gabriel Mountain Range and enforce policies to ensure that opportunities to enjoy scenic views are either preserved or enhanced. The proposed project primarily focuses on improving the quality of the visual experience for future development (e.g., through high-quality materials and architectural articulation) but would not increase building height or intensity beyond the limits set by the underlying zoning and land use designations. Furthermore, the proposed project would not introduce any new mechanism for obstructing scenic vistas or viewsheds beyond what was already considered in the Certified EIR. Therefore, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts on scenic vistas.

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(b) Except as provided in Public Resources Code Section 21099, would the proposed project substantially damage scenic resources, including, but not limited to, trees, rock outcroppings, and historic buildings within a state scenic highway? The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to scenic resources, including those within a state scenic highway.

The proposed project is an implementing regulatory tool that applies to future construction and does not change the physical location of designated state scenic highways or the protection status of adjacent scenic resources, such as protected trees (as discussed in Section 3.3, Biological Resources) or historic buildings (see Section 3.4, Cultural Resources). The Certified EIR states there are no adopted State scenic highways located in the City. However, the portion of SR-57 adjacent to the western boundary of the City’s Sphere of Influence and from the City limits to SR57’s confluence with SR-60 is eligible for official scenic highway status. As discussed in the Certified EIR, the General Plan 2040’s land use changes along this portion of SR-57 are minimal, given that these portions of the highway are adjacent to developed areas and views would not be obstructed. Furthermore, the proposed project promotes a more visually appealing built environment that minimizes the visual distraction of substandard development near scenic areas.

Therefore, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts on scenic resources within a state scenic highway.
(c) Except as provided in Public Resources Code Section 21099, would the proposed project, in nonurbanized areas, substantially degrade the existing visual character or quality of public views of the site and its surroundings? (Public views are those that are experienced from publicly accessible vantage point). If the proposed project is in an urbanized area, would the project conflict with applicable zoning and other regulations governing scenic quality?
The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to potential conflicts with applicable zoning and other regulations governing scenic quality in an urban area. The ODS is intended to achieve the design goals set forth in the General Plan 2040. The ODS is intended to ensure visual quality enhancement by setting specific, objective standards for architectural management. For instance, the Building Articulation Standards (Section 3 of the ODS) include measures such as the “Vertical Plane Break” to reduce building bulk and monotony, while the definition of Frontage Types (Section 4 of the ODS) ensures that buildings are constructed with a positive, human-scale relationship to the public streetscape (Appendix A). These standards support high quality street-facing facades and material durability. Therefore, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts on scenic quality in an urban area.

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(d) Except as provided in Public Resources Code Section 21099, would the proposed project create new sources of substantial light or glare which would adversely affect day or nighttime views in the area?
The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to light and glare. The Certified EIR analyzed the potential increase in light and glare associated with the overall planned development and concluded that future development resulting from the General Plan 2040 would necessitate the use of additional light fixtures, such as residential and non-residential interior and exterior lighting, parking lot lighting, commercial signage lighting, lamps for streetscape and public recreation areas. The proposed project would reduce potential future light and glare by providing specific standards, such as prohibiting highly reflective window glazing and requiring compliance with Section 22.16.050 (Exterior Lighting) of the Diamond Bar City Code. Future development guided by the proposed project would be subject to standards that include the placement, shielding, and intensity of outdoor lighting (e.g., mandatory use of downward-facing, fully shielded light fixtures to prevent light spillover onto adjacent properties) and material selection (e.g., limitations on the use of highly reflective materials, such as mirrored glass, to control solar glare). Also, the Diamond Bar City Code contains provisions that would limit the light and glare for future residential and nonresidential development.

Therefore, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts from new sources of light or glare.

Mitigation Measures
As with the Certified EIR, no mitigation measures have been identified related to aesthetics. No further mitigation measures are required.

Cumulative Impact Analysis
There are no new circumstances involving new cumulatively considerable aesthetics impacts for the proposed project that were not previously analyzed in the Certified EIR. As evaluated in the Certified EIR, impacts on aesthetics would not be cumulatively considerable. Consistent with the findings of the Certified EIR, impacts in relation to aesthetics would not be cumulatively considerable with implementation of the proposed project, when compared to the General Plan 2040. Therefore, the proposed project would not result in any new significant environmental cumulative impacts or a substantial increase in the severity of previously identified significant cumulative impacts related to aesthetics.

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3.2 AIR QUALITY
This section evaluates the effects on air quality from the proposed project. This Addendum relies on and incorporates by reference the project setting and regulatory setting as described in Section

3.2, Air Quality, of the Certified EIR. Potential impacts to air quality from the proposed project are discussed relative to conclusions in the Certified EIR. The Certified EIR determined that the implementation of the General Plan 2040 would result in significant and unavoidable air quality impacts. In addition, mitigation measures for construction and future development would be required, in conjunction with future project approvals, to reduce cumulative impacts of a considerable net increase of criteria pollutants (for which the region is in non-attainment under an applicable federal or state ambient air quality standards), and exposure of sensitive receptors to substantial pollutant concentrations. Consistent with the Certified EIR, air quality for the proposed project was evaluated with regard to the General Plan 2040, the South Coast Air Quality Control District (SCAQMD) significance thresholds, the California Ambient Air Quality Standards (CAAQS), and the National Ambient Air Quality Standards (NAAQS). A review of available records and literature determined that no new air quality information has become available since the certification of the EIR.

3.2.1 Setting
The environmental setting for air quality is functionally the same as described in the Certified EIR.

Data on existing air quality in the South Coast Air Basin (SCAB), where the proposed project is located, are collected by a network of air monitoring stations operated by the California Air Resources Board (CARB).

The regulatory framework plans pertaining to air quality have been updated at the regional level since the preparation of the Certified EIR, including updates to the SCAQMD Air Quality Management Plan (AQMP) and the Southern California Association of Governments (SCAG) Regional Transportation Plan/Sustainable Communities Strategy (Connect SoCal). The 2022 AQMP is the most recent version of the AQMP. When compared to the 2012 and 2016 AQMPs discussed in the Certified EIR, the 2022 AQMP focuses on updates related to the attainment of the 2015 8-hour ozone standard, introduces new control measures that primarily emphasize stationary sources, and newer modeling techniques. In addition, the 2024 Connect SoCal is the most recent Regional Transportation Plan/Sustainable Communities Strategy prepared by SCAG.6 When compared to the 2016 Regional Transportation Plan/Sustainable Communities Strategy discussed in the Certified EIR, the 2024 Connect SoCal provides new focus areas for equity, resilience, and housing; addresses new challenges; and details strategies for mobility, communities, the environment, and the economy. While these regional plan updates are reviewed for consistency, they would not result in substantial changes to the regional framework analyzed under air quality and would not result in changes to the findings in the Certified EIR.

Federal, state, and local regulations remain unchanged when compared to the Certified EIR. The Environmental Protection Agency (EPA), CARB, and the local air districts classify an area as attainment, unclassified, or nonattainment depending on whether or not the monitored ambient air quality data shows compliance, insufficient data available, or noncompliance with the ambient air quality standards, respectively. The NAAQS and CAAQS relevant to the proposed project include the following criteria pollutants: ozone, fine particulate matter with an aerodynamic 6 Southern California Association of Governments. 2024. Connect SoCal: A Plan for Navigating to a Brighter Future. https://scag.ca.gov/sites/default/files/2024-05/23-2987-connect-socal-2024-final-complete-040424.pdf (accessed October 30, 2025).

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diameter of 10 microns in size or less (PM10), fine particulate matter with an aerodynamic diameter of 2.5 microns in size or less (PM2.5), carbon monoxide (CO), nitrogen dioxide (NO2), and sulfur dioxide (SO2). These standards, along with regional thresholds of significance, are regulated and enforced by SCAQMD in the City. Compared to the NAAQS, the Los Angeles County portion of the SCAB is a nonattainment area for 1-hour ozone, 8-hour ozone, PM2.5, and lead for nearsource monitors.7 Designations for attainment are determined from the ambient air quality.

Compared to the CAAQS, the Los Angeles County portion of the SCAB is a nonattainment area for 1-hour ozone, 8-hour ozone, PM2.5, and PM10.
8 3.2.2 Impact Analysis
Project Impact Analysis
The potential for the proposed project to result in a new significant impact or a substantial increase in the severity of previously identified significant impacts to air quality was evaluated in relation to the following questions as stated in Appendix G of the 2025 State CEQA Guidelines:
(a) Would the proposed project conflict with or obstruct implementation of the applicable air quality plan?
The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to conflicts with or the obstruction of implementation of the applicable air quality plan. The proposed project would set new minimum design standards for future multifamily and mixed-use development throughout the City (please see Section 2, Project Description). In addition, the use of the proposed project on future multifamily and mixed-use development would be subject to project-specific development review requirements and compliance with existing regulations that focus on improving air quality, including the SCAQMD rules and regulations, the General Plan 2040 goals and policies for air quality, and SCAG’s Connect SoCal. New development would be subject to compliance with the most recent AQMP and Connect SoCal. The proposed project does not conflict with the most recent updates to these air quality plans. With respect to the 2022 AQMP, implementation of objective design standards for multifamily and mixed-use development would not conflict with attainment of the 2015 8-hour ozone standard, control measures for stationary sources, or newer modeling techniques. With respect to the 2024 Connect SoCal, implementation of objective design standards for multifamily and mixed-use development would not conflict with new focus areas for equity, resilience, and housing; nor would it conflict with strategies for mobility, communities, the environment, and the economy. The proposed project would not result in an increase in population, growth, or additional development beyond the Certified EIR buildout; nor would it result in an increase in vehicle miles traveled (VMT). Therefore, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to any conflicts with or obstruction of implementation of the applicable air quality plan. 7 U.S. Environmental Protection Agency. 2023. Nonattainment Areas for Criteria Pollutants. https://www.epa.gov/green-book (accessed October 24, 2025). 8 California Air Resources Board. 2022. Area Designations Maps / State Ambient Air Quality Standards. http://www.arb.ca.gov/desig/adm/adm.htm (accessed October 24, 2025).

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(b) Would the proposed project result in a cumulatively considerable net increase of any criteria pollutant for which the project region is non-attainment under an applicable federal or state ambient air quality standard?
The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to the cumulatively considerable net increase of any criteria pollutant for which the project region is non-attainment under an applicable federal or state ambient air quality standard. The Certified EIR found that the General Plan 2040 would exceed SCAQMD significance thresholds for volatile organic compounds (VOCs) and nitrogen oxides (NOx), and that construction and operational impacts would be significant and unavoidable based on the potential for the General Plan 2040 to result in a cumulatively considerable net increase of a criteria pollutant for which the City is in nonattainment under the NAAQS and CAAQS. Compared to the NAAQS, the Los Angeles County portion of the SCAB is a nonattainment area for 1-hour ozone, 8-hour ozone, PM2.5, and lead for near-source monitors.9 Designations for attainment are determined from the ambient air quality. Compared to the CAAQS, the Los Angeles County portion of the SCAB is a nonattainment area for 1-hour ozone, 8-hour ozone, PM2.5, and PM10. 10 The application of the proposed project to future multifamily and mixed-use development within the City would be consistent with the construction phases, activities, and anticipated construction equipment outlined in the Certified EIR (please see Section 2). The application of the proposed project to future multifamily housing and mixed-use development would be subject to projectspecific development review requirements and compliance with existing regulations that focus on improving air quality. Similar to the Certified EIR, mitigation measures MM-AQ-1 and MM-AQ-2 would apply to any future developments subject to the proposed project and require such future development projects implemented under the General Plan 2040 to demonstrate consistency with SCAQMD construction and operation emissions thresholds.

Criteria pollutant construction and operation emissions from the application of the proposed project to future multifamily and mixed-use development would not change the significant and unavoidable impact conclusion from the Certified EIR. Construction and operation emissions would be reduced to the maximum extent practicable with incorporation of mitigation measures, as specified in the Certified EIR. Because the proposed project would not result in additional development beyond the remaining Certified EIR buildout and be subject to mitigation measures MM-AQ-1 and MM-AQ-2, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to a cumulatively considerable net increase of any criteria pollutant for which the project region is nonattainment under an applicable federal or state ambient air quality standard. (c) Would the project expose sensitive receptors to substantial pollutant concentrations? The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to exposing sensitive receptors to substantial pollutant concentrations. The Certified EIR found that the General Plan 2040 would expose sensitive receptors to substantial pollutant concentrations and that construction and operational impacts would be significant and unavoidable. According to the General Plan 2040, sensitive receptors 9 U.S. Environmental Protection Agency. 2023. Nonattainment Areas for Criteria Pollutants. https://www.epa.gov/green-book (accessed October 24, 2025). 10 California Air Resources Board. 2022. Area Designations Maps / State Ambient Air Quality Standards. http://www.arb.ca.gov/desig/adm/adm.htm (accessed October 24, 2025).

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include residences, hospitals, schools, daycare facilities, playgrounds, parks and other recreational facilities, elderly housing, and other medical care facilities.11 Construction and operation emissions associated with the application of the proposed project to future multifamily housing and mixed-use development could impact sensitive receptors in the City. While future individual development projects would require separate environmental assessments, the proposed project would be consistent with the construction phases, activities, and anticipated construction equipment outlined in the Certified EIR (see Section 2.5). As with the Certified EIR, development projects subject to the proposed project would also be subject to mitigation measure MM-AQ-1 to reduce impacts on sensitive receptors to substantial pollutant concentrations, which includes reducing toxic air contaminants and health impacts through a reduction of criteria pollutant emissions from the use of more efficient construction equipment.

Because the proposed project would not result in any additional development beyond the remaining Certified EIR buildout and any development subject to the proposed project would be also be subject to mitigation measure MM-AQ-1, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to the exposure of sensitive receptors to substantial pollutant concentrations. (d) Would the proposed project result in other emissions (such as those leading to odors) adversely affecting a substantial number of people?
The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to other emissions (such as those leading to odors) adversely affecting a substantial number of people. The Certified EIR found that the General Plan 2040 would result in significant and unavoidable impacts on air quality in relation to other emissions adversely affecting a substantial number of people, including regional emissions for CO. No mitigation measures were identified in the Certified EIR. With respect to odors during construction and operation, the Certified EIR determined that impacts would be less than significant. The SCAQMD CEQA Air Quality Handbook defines potential odor issues that generally occur from the following land uses: wastewater treatment plants, food processing plants, agricultural uses, chemical plants, composting, refineries, landfills, dairies, and fiberglass moldings. The proposed project merely regulates visual design and would set new minimum design standards for future multifamily and mixed-use development throughout the City (see Section 2.2). None of the land uses stated in the SCAQMD CEQA Air Quality Handbook would apply to future multifamily and mixed-use development. Compared to the General Plan 2040, the proposed project’s land uses are consistent with the proposed land uses previously evaluated. As discussed, future multifamily and mixed-use development subject to the proposed project would also be subject to projectspecific development review requirements and compliance with existing regulations that focus on improving air quality, including the SCAQMD rules and regulations. Examples of applicable SCAQMD rules and regulations include Rule 402, Nuisance, to avoid causing injury to adjacent sensitive receptors; and Rule 1113 for controlling VOC emissions from the application of architectural coatings.

Because the proposed project would not result in additional development beyond what was analyzed in the Certified EIR, the proposed project would not result in a new significant impact or 11 City of Diamond Bar. 2019. Diamond Bar General Plan 2040. https://www.diamondbarca.gov/DocumentCenter/View/7072/Diamond-Bar-General-Plan-2040?bidId= (accessed October 23, 2025).

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a substantial increase in the severity of previously identified significant impacts related to other emissions (such as those leading to odors) adversely affecting a substantial number of people.

Mitigation Measures
As with the Certified EIR, mitigation measures MM-AQ-1 and MM-AQ-2 are required for implementation in order to lessen and/or alleviate the impacts related to air quality expected to result from implementation of the proposed project (Appendix B).

No further mitigation measures are required.

Cumulative Impact Analysis
The Certified EIR found that impacts to air quality in relation to long-term regional emissions would be cumulatively considerable. The proposed project is a design overlay that works within the regulatory framework and cumulative growth assumptions of the Certified EIR and is consistent with the analysis of cumulative impacts under the development evaluated in the General Plan 2040.

Consistent with the findings of the Certified EIR and analysis above, impacts to air quality from the proposed project in relation to long-term regional emissions would remain cumulatively considerable. The proposed project would not result in a new significant cumulative impact or a substantial increase in the severity of previously identified significant cumulative impacts in relation to air quality.

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3.3 BIOLOGICAL RESOURCES
This section evaluates the potential environmental effects of the proposed project on biological resources. This analysis determines if the proposed project would result in a new significant impact or a substantial increase in the severity of previously identified significant impacts as compared to Section 3.3, Biological Resources, of the Certified EIR. Potential impacts to biological resources from the proposed project are discussed relative to the conclusions in the Certified EIR. The Certified EIR determined that the implementation of the General Plan 2040 would result in less than significant impacts to biological resources with mitigation incorporated.

Mitigation measures for construction and future development would be required in conjunction with future project approvals. Consistent with the Certified EIR, biological resources for the proposed project were evaluated with regard to the State of California Fish and Game Code; the California Native Plant Society (CNPS) online inventory; and the Diamond Bar City Code, Chapter

22.38, Tree Preservation and Protection.

3.3.1 Setting
The project setting for biological resources is the same as that considered in the Certified EIR. A review of available records and literature determined that no new biological resources, conservation policies, or ordinances have become available since certification of the EIR.

3.3.2 Impact Analysis
Project Impact Analysis
The potential for the proposed project to result in a new significant impact or a substantial increase in the severity of previously identified significant impacts to biological resources was evaluated in relation to the following questions as stated in Appendix G of the 2025 CEQA Guidelines. (a) Would the proposed project have a substantial adverse effect, either directly or through habitat modifications, on any species identified as a candidate, sensitive, or special status species in local or regional plans, policies, or regulations, or by the California Department of Fish and Wildlife or U.S. Fish and Wildlife Service? The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to a substantial adverse effect on candidate, sensitive, or special status species. The proposed project would be subject to the existing General Plan policies and the required mitigation measures. The Certified EIR concluded that with the implementation of mitigation measures MM-BIO-1A through MM-BIO-1K, the potentially significant impacts on candidate, sensitive, or special status species would be minimized to a less than significant level.

The proposed project does not propose new development and would not alter the land use designations and growth projections analyzed in the Certified EIR. The proposed project does not increase the overall development capacity, modify the General Plan land use boundaries, or change the level of intensity that was the basis for the Certified EIR’s analysis. The proposed project does not authorize any new ground disturbance or habitat loss beyond the scope of the Certified EIR, which requires project-specific implementation of mitigation measures (MM-BIO-1A through MM-BIO-1K) to avoid or minimize impacts to sensitive species. With adoption of the proposed project, all development that would be subject to the ODS would also be subject to MMBIO-1A through MM-BIO-1K. As the proposed project would not result in additional development

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or induce growth greater than what was considered in Certified EIR and be subject to mitigation measures MM-BIO-1A through MM-BIO-1K, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to candidate, sensitive, or special status species. (b) Would the proposed project have a substantial adverse effect on any riparian habitat or other sensitive natural community identified in local or regional plans, policies, regulations or by the California Department of Fish and Wildlife or U.S. Fish and Wildlife Service? The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to a substantial adverse effect on any riparian habitat or other sensitive natural community. The proposed project is limited in its application to existing urban corridors within the City. The proposed project is not applicable to the City’s open space, canyon, or hillside areas where sensitive natural communities, such as riparian habitats or coastal sage scrub, are typically located. The Certified EIR identified significant impacts to these sensitive communities and adopted comprehensive General Plan policies and mitigation measures MMBIO-2 through MM-BIO-5 that prohibit or heavily restrict development within these areas. The Certified EIR concluded that with the implementation of these measures, the potentially significant impacts on sensitive natural communities, including oak woodlands, walnut woodlands, riparian, and sage scrub habitats, would be minimized to a less than significant level. With the adoption of the proposed project, all development that would be subject to the ODS would also be subject to MM-BIO-2 through MM-BIO-5. Given that the proposed project is a set of design standards and does not facilitate or authorize new development in biologically sensitive locations, the proposed project would not introduce a new or increased level of impact to these protected communities.

The proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to potential impacts on riparian habitat or other sensitive natural communities.
(c) Would the proposed project have a substantial adverse effect on state or federally protected wetlands (including, but not limited to, marsh, vernal pool, coastal, etc.) through direct removal, filling, hydrological interruption, or other means? The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to a substantial adverse effect on state or federally protected wetlands. The proposed project would be subject to the full regulatory framework and the required site-specific mitigation process applicable to state or federally protected wetlands. The Certified EIR identifies the potential for extensive wetland areas, such as those extending upstream from Arnold Reservoir north of Grand Avenue in the Tres Hermanos portion of the City, to be impacted by the General Plan 2040. The Certified EIR also identified potential impacts to the bed and banks of creeks and their tributaries. However, the Certified EIR explicitly concluded that the implementation of General Plan policies (e.g., LU-P-2, LU-P-56, RC-P-25, RC-P-26) and the application of mitigation measures MM-BIO-2 and MM-BIO-3 would ensure that impacts on federally and state protected wetlands are reduced to a less than significant level. These mitigation measures ensure that any unavoidable loss of jurisdictional features is fully compensated for and approved under the purview of state and federal resource agencies. With the adoption of the proposed project, all development that would be subject to the ODS would also be subject to MM-BIO-2 and MM-BIO-3. The proposed project does not change the physical environment, the regulatory requirements, or the mandatory mitigation measures imposed on future development. Therefore, the proposed project would not result in a new significant impact

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or a substantial increase in the severity of previously identified significant impacts related to state or federally protected wetlands.
(d) Would the proposed project interfere substantially with the movement of any native resident or migratory fish or wildlife species or with established native resident or migratory wildlife corridors, or impede the use of native wildlife nursery sites? The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to interfering with the movement of any native resident or migratory fish or wildlife species; interfering with established native resident or migratory wildlife corridors; or impeding the use of native wildlife nursery sites. The proposed project, developed under the provisions of the General Plan 2040, is consistent with the impacts and mitigation identified in the Certified EIR. The Certified EIR found impacts to wildlife movement to be potentially significant before mitigation. The Certified EIR determined that impacts to wildlife movement would be reduced through consistency with General Plan policies for Open Space and Resource Conservation (specifically referencing RC-P-1, RC-P-9, RC-P-12, and RC-P-24), which address maintenance of the Chino Hills (east) and the Puente Hills (west) wildlife movement corridors and local corridors. The Certified EIR determined that compliance with mitigation measure MM-BIO-6 for the Tonner Canyon wildlife corridor and adherence to General Plan 2040 policies would reduce impacts on wildlife movement to a less than significant level. The proposed project would not change the land use, density, or physical boundaries near these critical corridors; therefore, it would not introduce new barriers or increase fragmentation, and it would not introduce new incompatible land uses next to wildlife movement corridors. Furthermore, the proposed project would not apply to development in open space areas or other areas anticipated to contain wildlife corridors, as the development subject to the proposed project is located on parcels designated for multifamily residential housing and mixed-use. With the adoption of the proposed project, all development that would be subject to the ODS would also be subject to MM-BIO-6. Therefore, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to wildlife movement. (e) Would the proposed project conflict with any local policies or ordinances protecting biological resources, such as a tree preservation policy or ordinance? The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to local biological resource protection policies, such as tree preservation policies or ordinances. The Certified EIR determined that due to regulatory compliance with existing policies, the City Tree Preservation Ordinance and the Los Angeles County Oak Tree Protection Ordinance, no significant impacts would occur, and no mitigation measures were required. Similar to the Certified EIR, the proposed project would be required to comply with the City of Diamond Bar Tree Preservation Ordinance and the Los Angeles County Oak Tree Protection Ordinance. Furthermore, the proposed project includes a provision that actively supports the goals of local greening policies by requiring that “at least 25 percent of the required on-site outdoor space shall be planted with ground cover, shrubs, trees, or a combination thereof.” This mandatory landscaping requirement reinforces the City’s commitment to enhancing the urban canopy and ensuring biological compatibility within development standards. All future projects subject to the proposed project would be required to obtain necessary permits and comply with all applicable sections of the Diamond Bar Development Code, which includes the City Tree Preservation Ordinance. Therefore, the proposed project would not result in a new

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significant impact or a substantial increase in the severity of previously identified significant impacts related to local policies or ordinances protecting biological resources. (f) Would the proposed project conflict with the provisions of an adopted Habitat Conservation Plan, Natural Community Conservation Plan, or other approved local, regional, or state habitat conservation plan?
The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to a conflict with an adopted conservation plan. The Certified EIR found that the General Plan 2040 would result in potential conflicts with the Puente-Chino Hills Wildlife Corridor Conservation Program led by the Wildlife Corridor Conservation Authority (WCCA). The EIR concluded that compliance with the adopted General Plan policies and mitigation measure MM-BIO-6 would reduce impacts below the level of significance. The proposed project specifies the aesthetic and functional design of buildings and sites within areas already designated for development. The proposed project does not alter the underlying commitment to comply with the terms of any adopted or future Habitat Conservation Plan (HCP) or Natural Community Conservation Plan (NCCP). The adoption of the proposed project would not create a conflict with the provisions of any adopted habitat conservation plan and would be consistent with the scope of impact analyzed in the Certified EIR. Furthermore, the proposed project would not apply to development in open space areas or other areas anticipated to be subject to the Puente-Chino Hills Wildlife Corridor Conservation Program, as the development subject to the proposed project is located on parcels designated for multifamily residential housing and mixed-use. However, if any future projects subject to the proposed project are located within the Puente-Chino Hills Wildlife Corridor Conservation Program area, they would be required to implement the General Plan 2040 policies and MM-BIO-6. Therefore, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to local, regional, or state habitat conservation plans.

Mitigation Measures
As with the Certified EIR, mitigation measures MM-BIO-1 through MM-BIO-6 are required for implementation in order to lessen and/or alleviate the impacts related to biological resources expected to result from implementation of the proposed project (Appendix B).

No further mitigation measures are required.

Cumulative Impact Analysis
There are no new circumstances involving new impacts to biological resources for the proposed project that were not previously analyzed in the Certified EIR. As evaluated in the Certified EIR, the General Plan 2040 would contribute incrementally to the continuing reduction in relatively natural, undisturbed open space areas and contribute to the progressive fragmentation of habitat areas and decline in species diversity throughout the region; however, overall cumulative impacts were determined to be less than significant with incorporation of mitigation measures MM-BIO-1 through MM-BIO-6. Consistent with the findings of the Certified EIR, cumulative impacts to biological resources would remain less than significant with implementation of the proposed project, when compared to the General Plan 2040. The proposed project is constrained by the land use and environmental parameters already established and analyzed in the Certified EIR.

The proposed project would not propose new development, increase development intensity, or alter the location of planned development. The contribution of development subject to the

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proposed project to the regional cumulative effect is consistent with the scope previously evaluated and mitigated in the Certified EIR. Therefore, the proposed project would not contribute to incremental cumulative biological resource impacts greater than the contribution analyzed in the Certified EIR with the application of standard regulatory compliance and existing mitigation measures. The proposed project would not result in a new significant cumulative impact or a substantial increase in the severity of previously identified significant cumulative impacts related to biological resources.

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3.4 CULTURAL RESOURCES
This section evaluates the potential environmental effects of the proposed project on cultural resources. This Addendum relies on and incorporates by reference the project and regulatory setting as described in Section 3.4, Cultural, Historic, and Tribal Cultural Resources, of the Certified EIR. Potential impacts to cultural resources from the proposed project are discussed relative to conclusions in the Certified EIR. The Certified EIR determined that the implementation of the General Plan 2040 would result in significant and unavoidable impacts to historical resources, less than significant impacts with mitigation to archaeological resources, and less than significant impacts to human remains. Mitigation measures for construction and future development would be required in conjunction with future project approvals.

3.4.1 Setting
The environmental setting for cultural resources is consistent with what was described in the Certified EIR. The historic setting, historical resources, archaeological resources, and data available for the presence of human remains are the same for the proposed project as those described in the Certified EIR. The regulatory setting applicable to cultural resources presented in the Certified EIR, including the National Historic Preservation Act, National Register of Historic Places, California Register of Historic Resources, and all applicable federal, state, and local regulations are the same and apply to the proposed project.

3.4.2 Impact Analysis
Project Impact Analysis
The potential for the proposed project to result in a new significant impact or a substantial increase in the severity of previously identified significant impacts on historical resources was evaluated in relation to the following questions as stated in Appendix G of the 2025 CEQA Guidelines. (a) Would the proposed project cause a substantial adverse change in the significance of a historical resource pursuant to §15064.5?
The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to historical resources. The Certified EIR determined that impacts would be significant and unavoidable, as anticipated development in the City could result in a substantial change in the significance of a historical resource through physical demolition, destruction, relocation, or alteration of the resource.

Consistent with the Certified EIR, future development subject to the proposed project would continue to be subject to mitigation measure MM-CULT-1. With the implementation of MM-CULT1, impacts to historical resources would be reduced; however, the impact would remain significant because historical resources could be demolished or altered in a manner such that they are no longer able to convey their historical significance.

All future development subject to the proposed project was considered in the Certified EIR. As the proposed project would not result in additional development beyond what was considered in the Certified EIR, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to historical resources as defined in State CEQA Guidelines Section 15064.5.

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(b) Would the proposed project cause a substantial adverse change in the significance of an archaeological resource pursuant to § 15064.5?
The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to archaeological resources. The Certified EIR determined that impacts would be less than significant with mitigation measure MM-CULT-2 incorporated, as future development anticipated by the General Plan 2040 would include construction-related ground disturbance that could disturb previously unknown prehistoric or historic era archaeological resources. Consistent with the Certified EIR, future development subject to the proposed project would continue to be subject to MM-CULT-2.

The proposed project would not result in additional development beyond what was considered in the Certified EIR; therefore, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to archaeological resources as defined in State CEQA Guidelines Section 15064.5. (c) Would the proposed project disturb any human remains, including those interred outside of dedicated cemeteries?
The proposed project would not exceed General Plan 2040 assumptions, and it would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts in relation to disturbing human remains. The Certified EIR determined that it is possible that unknown prehistoric or historic era human remains could be encountered during construction-related ground disturbance, but impacts would be less than significant through regulatory compliance.

Consistent with the Certified EIR, any human remains encountered would be handled in accordance with California Health and Safety Code Section 7050.5. If the human remains are Native American, they would be handled in accordance with Public Resources Code Section 5097.98.

Therefore, the proposed project would not result in a new significant impact or a substantial increase in the severity of previously identified significant impacts related to human remains.

Mitigation Measures
As with the Certified EIR, mitigation measures MM-CULT-1 and MM-CULT-2 are required for implementation in order to reduce the impacts related to cultural resources expected to result from implementation of the proposed project (Appendix B).

No further mitigation measures are required.

Cumulative Impact Analysis
There are no new circumstances involving new impacts to cultural resources for the proposed project that were not previously analyzed in the Certified EIR. As discussed in the Certified EIR, cumulative impacts to historical resources would be significant and the contribution of General Plan 2040 would be cumulatively considerable despite the implementation of mitigation measure MM-CULT-1. With respect to archaeological resources, the Certified EIR determined that the

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cumulative impact would be significant and the contribution of General Plan 2040 would be cumulatively considerable. With respect to human remains, the Certified EIR determined that the cumulative impact would be less than significant. The contribution of the proposed project to the regional cumulative effect is consistent with the scope previously evaluated and mitigated in the Certified EIR. Therefore, the proposed project would not contribute to incremental cumulative cultural resource impacts greater than the contribution analyzed in the Certified EIR for human remains, and the cumulative impact remains less than significant with the application of standard regulatory compliance. The proposed project would not result in additional development beyond what was considered in the Certified EIR; therefore, the proposed project would not result in a new significant cumulative impact or a substantial increase in the severity of previously identified cumulative significant impacts related to cultural resources.

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Diamond Bar City CouncilMarch 17, 2026

Diamond Bar City Council
March 17, 2026