PUBLIC DRAFT
December 05, 2025
R3 Design Handbook
Attachment 4
Introduction 3
Guiding Principles 3
Key Concepts and Terms 3
Expected Outcomes 9
R3-A 10
R3-B 14
R3-C 19
R3-D 23
Table of Contents
Prepared for:
City of Mountain View Planning Division
City Hall, First Floor
500 Castro Street
Mountain View, CA 94041
650.903.6306
Prepared by:
Opticos Design, Inc.
2100 Milvia Street; Suite 125
Berkeley, California 94704
510.558.6957
Introduction
The R3 Design Handbook is a visual
representation of the intented outcomes
generated by the updated R3 Zone
Standards.
This Handbook reflects the R3 zone standards, which are intended to generate pedestrian-oriented buildings, streetscapes, and public spaces that improve the sense of place across the various neighborhoods where the R3 zone occurs. The standards are applied through sub-districts that promote distinct but complementary physical character across the R3- zoned parcels. The sub-districts in the R3 zone include R3-A, R3-B, R3-C, and R3-D.
Key Concepts and Terms
"House-Scale"
House-scale buildings are those that match the size and scale of a typical house, in terms of width, depth, height, and architectural details. Housescale buildings are typically a maximum 2.5 stories tall, such as single-family houses, duplexes, triplexes, fourplexes, small multiplexes, cottage courts, and courtyard buildings. Building widths of these types range from 25 feet to 75 feet overall, including wings. House-scale buildings fit best in low-intensity residential zones.
Walkable Neighborhoods
Walkable neighborhoods are places where a resident can access most daily needs within a ½ mile, or a 5 to 10 minute walk. These environments allow automobiles but, because of the proximity to food, services, and shopping, don't require one for every trip.
"Walkable" does not mean recreational walking on a path or trail, but rather walking to a destination—like work, services, a coffee shop, restaurant, bar, entertainment, or other amenity.
Half-Story
A half-story is an occupiable floor that is contained under the roof volume or a basement that is partially above grade. "Block-Scale"
The footprint of a block-scale building occupies most of, if not all of, a city block; or, when multiple buildings are arranged together along a street, appear as long as most or all of a block. Examples include mixed-use buildings, large multiplexes, and townhouses. Block-scale buildings are most appropriate in downtowns, centers, moderate-to-high-intensity neighborhoods, and along major corridors.
Guiding Principles
Five guiding principles informed the update
to the R3 standards.
1. Housing that provides opportunities for a variety of unit sizes, configurations, amenities and costs, allowing residents to find homes that work best for them.
2. Pedestrian-friendly neighborhoods with comfortable sidewalks, new paths through large blocks (where feasible), easily accessible building entrances, and frontages with appeal and interest.
3. Commercial appropriate to the character of a residential district, that improves access to daily goods and supports neighborhood identity.
4. Context-sensitive buildings address character, shadow, privacy and other impacts to surrounding homes.
5. Public-facing landscaped open areas that support tree canopy, and reduce the visual impact of taller buildings.
Proximity to neighborhood retail, open space, and civic buildings helps to support walkable neighborhoods.
Key
5 min. walk
10 min. walk
Residential
Neighborhood Retail
Civic/Institutional
Park/Open Space
Dormer
Half-Story
6 Units
24 Units
3 GUIDING PRINCIPLE
Housing that provides opportunities for a variety of unit sizes, configurations, amenities and costs, allowing residents to find homes that work best for them.
GUIDING PRINCIPLE
Pedestrian-friendly neighborhoods with comfortable sidewalks, new paths through large blocks (where feasible), easily accessible entrances, and frontages with appeal and interest.
GUIDING PRINCIPLE
Commercial appropriate to the character of a residential district, that improves access to daily goods and supports neighborhood identity.
GUIDING PRINCIPLE
Context sensitive buildings address character, shadow, privacy and other impacts to surrounding homes.
GUIDING PRINCIPLE
Public-facing landscaped open areas that support tree canopy, and reduce the visual impact of taller buildings.
EXPECTED OUTCOMES
R3 Zone Sub-Districts
R3-A
is a walkable
neighborhood
environment of
detached buildings
up to 2.5 stories, small
building footprints,
and low-intensity
housing choices.
10 Building Height.
scale in footprint and height with
pitched or flat roofs contributing to a
Buildings are house- R3-A
low-intensity neighborhood feel.
Open Space. Rear yards
provide outdoor shared space.
Setback. Buildings are
setback at least 20 feet
and include building entry
elements such as this Porch.
Building Entries. Buildings are entered
through a variety of building entry types
such as this shared Stoop, adding identity to
each building and a direct connection to the
public realm.
Parking Location.
Parking is located away
from the front of the lots
to emphasize pedestrianoriented buildings.
11 Building Width. Building widths
are up to 60 feet, emphasizing the
house-scale character of R3-A.
Building Entries. This Stoop
building entry is one of
several allowed types in R3-
A: Stoop, Dooryard, Terrace,
Porch, Common Entry.
Setback. Buildings are setback at least 20
feet and include building entry elements to
connect the building and residents with the
public realm.
R3-A
12 Building Height. A third story is
allowed when completely under a
pitched roof up to 35 feet.
Building Entries. Porches are one of 5 allowed
buidling entry types in R3-A, providing a variety of
entry elements along the streetscape.
Parking Setback. Parking is located away
from the front of buildings to reinforce a
more pedestrian-oriented streetscape.
R3-A
13 R3-B
is a walkable
neighborhood
environment of
detached buildings up
to 3 stories, medium
building footprints,
and low-to-moderateintensity housing
choices.
14 Building Height.
are up to 3 stories with a flat
or pitched roof.
Buildings R3-B
Buildings. Buildings are
setback at least 15 feet,
detached from other
buildings, and up to 100 feet
wide, reflecting the low-tomedium intensity of R3-B.
Building Entries. New
buildings include at least
one building entry type
such as the Dooryard
shown here or a Terrace,
Porch, or Stoop. Some
buildings include more
than one building entry
type. Each building entry
type directly connects
the residents with
the streetscape while
providing visual interest
and activity.
15 Buildings. Buildings are
up to 100 feet wide and
detached reflecting a
low-to-medium intensity
and scale.
Building Design. At certain horizontal lengths and
heights, facades must include massing features to
visually break down the building's overall massing. This example does not require massing features due to its
shorter length and number of allowed stories.
Setback. Buildings are
setback at least 15 feet
making room for a variety of
building entry types along
the streetscape (dooryard
shown).
R3-B
16 Building Height.
Buildings are up to
3 stories and have
a flat or pitched
roof.
Projecting Elements. Elements such as
bay windows and balconies are allowed to
encroach into required setbacks to maximize
the interior floor space while creating a
visually interesting streetscape consistent
with the R3-B character.
Building Entries.
Building entry elements
connect the residents
and the building to the
streetscape providing
walkability and visual
variety.
R3-B
17 R3-B Parking Location. Parking is accommodated
in ways that do not detract from the
streetscape. Allowed parking locations are a
certain distance from the front of the lot and
building. This example shows parking in the
rear of a lot.
Open Space. Shared on-site
open space is at the rear of
buildings with access on corner
lots to the adjacent streetscape.
Setback. Buildings are
setback at least 10 feet along
side streets making room for
a variety of building entry
types along the streetscape
(covered stoops shown).
Building Entries. New
buildings include a
variety of building entries
such as the Dooryard
shown here or a Porch,
a Terrace, or a Stoop.
These elements enhance
the building entry by
providing some space
in front and alongside
the entry for visitors or
residents to use. These
spaces also provide
for interaction with
pedestrians and cyclists
along the streetscape.
18 R3-C
is a walkable
neighborhood
environment of
detached buildings up
to 3.5 stories, mediumto-large building
footprints, and
moderate-intensity
housing choices.
19 Parking Location
(Subterranean).
Depending on the
number of spaces to
be provided, some
buildings locate
the parking in a
subterranean garage.
Building Height. Buildings
are up to 3.5 stories when
including a pitched roof
that encloses habitable
space.
Common Open Space.
Shared, on-site open space
ranges from courtyards
(shown) to passages along
the side property line
and areas at the rear of a
lot. These spaces work in
combination with ground
floor building entry elements
(porches, dooryards,
terraces) and balconies to
provide residents with open
space.
Building Entries. A variety of building entry
types enliven the streetscape and provide
shared areas for residents and visitors (porch
shown).
R3-C
20 Building Width.
120 feet wide and detached to reflect
a moderate intensity and physical
Buildings are up to R3-C
character.
Building Height. When buildings
include a pitched roof, the space
beneath can be habitable space,
adding more housing to the area.
Shared On-Site Open
Space. Courtyard buildings
provide a shared central
space for residents and
visitors while contributing
to the pattern of moderate
building widths along the
streetscape.
Setbacks. Although buildings are larger
in R3-C than in R3-B and R3-A, buildings
are setback at least 15 feet to reflect a
moderate intensity. Buildings connect to
the streetscape through a variety of building
entry elements (dooryards, terraces, stoops,
and porches).
21 Building Height.
are up to 3.5 stories when
including a pitched roof that
Buildings R3-C
encloses habitable space.
Setbacks. Although buildings are larger
in R3-C than in R3-B and R3-A, buildings
are setback at least 15 feet to reflect a
moderate intensity. Buildings connect to
the streetscape through a variety of building
entry elements (dooryards, terraces, stoops,
and porches).
Building Entries. New
buildings include a
variety of building entries
such as the Porch shown
here. These elements
enhance the building
entry by providing
some space in front and
alongside the entry for
visitors or residents to
use. These spaces also
provide for interaction
with pedestrians and
cyclists along the
streetscape.
22 R3-D
is a walkable
neighborhood
environment of
attached and
detached buildings
up to 6 stories, large
building footprints,
and high-intensity
housing choices.
23 Massing Features.
lengths, facades must include massing features
to visually break down the building's overall
massing. This example recesses a portion of the
At certain horizontal Building Height.
are up to 6 stories, depending
on the actual location (see
General Plan Land Use Map).
Buildings R3-D
wall for visual interest and variety.
Publicly Accessible Open
Space. Pedestrians can
enjoy a plaza at the street
corner and a green space
with a fountain and benches,
adding amenities and
interest to the streetscape.
Building Design. Buildings are designed to
visually organize facades into three parts:
base, middle, and top. The ground floor is
designed with lots of windows for visibility
out to the streetscape and interaction with
pedestrians.
Building Entries.
New buildings include
a variety of building
entries such as the
Dooryard shown here
or a Terrace or a Stoop.
These elements enhance
the building entry by
providing some space
in front and alongside
the entry for visitors or
residents to use. These
spaces also provide
for interaction with
pedestrians and cyclists
along the streetscape.
24 R3-D Massing Features. At certain horizontal
lengths, facades must include massing
features to visually break down the building's
overall massing. This example recesses a
portion of the wall for visual interest and
variety.
Parking Location. Buildings are
designed to locate parking at least
30 feet behind ground floor units or
behind the building to emphasize a
pedestrian-oriented streetscape.
Open Space. Open
space is provided
through a combination
of shared courtyards,
passages, balconies, and
building entry elements.
Building Entries. New
buildings include a
variety of building entries
such as the Dooryard
shown here. These
elements enhance
the building entry by
providing some space
in front and alongside
the entry for visitors or
residents to use. These
elements also provide
a pedestrian-oriented
and scaled ground floor
along the streetscape.
25 Building Design. Building facades are designed
to express three distinct but complementary
parts: a base, middle, and top. The base can
consist of one or more stories. The middle
consists of the most stories. The top can consist
of a prominent feature such as a cornice, part
of a story, or multiple stories. This approach
provides for creativity and visual interest.
Building Entries. Buildings are designed to activate the streetscape. Depending on the location, ground floor nonresidential space is allowed along with the corresponding building entry type such as the shopfronts shown here. The ground floor is designed with lots of windows for visibility out to the streetscape and interaction with pedestrians.
Pedestrian Connection.
Some blocks include
pedestrian passages
to a public open space
or through the block to
another street, increasing
the circulation network
for pedestrians and
cyclists.
Massing Features. Buildings over 3
stories and over 80 feet long must
include massing features. One of the
allowed features is a projection of at
least 3 feet for at least 10 horizontal feet
as shown here.
R3-D
26 Parking Location. The
pedestrian-oriented
streetscape is emphasized
by locating parking away
from the streetscape, behind
the building or at least
behind the ground floor
space.
Setbacks. Buildings are setback
from the sidewalk by at least 15
feet to establish a residential
character in the neighborhood.
Building Entries. New
buildings include a
variety of building entries
such as the Stoop and
Dooryard shown here
or a Porch or a Terrace.
These elements enhance
the building entry by
providing some space
in front and alongside
the entry for visitors or
residents to use. These
spaces also provide
for interaction with
pedestrians and cyclists
along the streetscape.
R3-D
27 Large-Canopy Trees. Trees along
all streetscapes provide shade, visual
interest and a transition in scale
between pedestrians and 4 to 6 story
buildings.
Building Entries. Pedestrian
Passages, like other
streetscapes, are lined with
ground floor building or unit
entries, enlivening the space.
Public Access
Easement. Depending
on the size or location of
a project, a Pedestrian
Passage is required
to provide access to
a public open space
and/or access through
the block to another
street. This increases the
circulation network for
pedestrians and cyclists.
R3-D
28 Open Space. Fifteen (15)
percent of the project site
must be provided as open
space. Open space may
be located for use by the
general public as the plaza
shown here.
Building Entries. The
ground floor along the
publicly accessible
open space must
have building and/or
unit entries to ensure
pedestrian activity. The
ground floor is allowed
to be residential or
non-residential.
R3-D
29