MEMORANDUM
DATE January 22, 2026
TO City of San Mateo
FROM PlaceWorks
SUBJECT Key Issues White Paper – Single-Family Residential Regulations Introduction
Single-family, low-density residential districts are evolving to meet the changing needs of Bay Area households. Today, more residents are working from home, families experiencing housing affordability constraints are more likely to include multiple generations living under one roof, and more older adults are choosing to age in place. To address these changes, California has introduced an increasing number of new housing legislation that aims to support the evolving needs of residents and address statewide housing shortages. Some of these laws aim to increase housing opportunities in single-family residential districts, including measures like Senate Bill (SB) 9, SB 1123, and more flexible accessory dwelling units (ADUs) regulation.
The regulations for the Single-Family Residential (R1) District are found in Chapter 27.18 in the City’s Zoning Code in Title 27 of the San Mateo Municipal Code (SMMC). This chapter, which has not been comprehensively updated since 1992, aims to create, preserve, and enhance single-family areas with larger yard areas. To comply with state law (SB 9), the City adopted Chapter 27.21 in 2022, creating a Two-Unit Development Residential Overlay District for R1 zones. This overlay provides specific regulations for two-unit developments and urban lot splits. The upcoming Comprehensive Zoning Code Update (CZCU) will update the R1 District (Chapter 27.18) to reflect recent best practices and state law, while retaining the existing SB 9 overlay district, which is currently consistent with State law.
This white paper includes a review of the existing single-family residential (SFR) regulations in the Zoning Code, directions and policies in the General Plan, recent state bills, best practice options and considerations, and questions to help facilitate public input on this topic.
City and Community Goals
The City has several goals for updating the current SFR regulations, including complying with recent state housing laws, converting subjective design guidelines into transparent and objective standards in the code and accompanying Objective Design Standards, simplifying development standards, and streamlining the approval process. Building a single-family home should be a clear and relatively easy January 22, 2026 | Page 2
process for someone unfamiliar with development who may only ever build or remodel a home once in their life. The City is seeking feedback on ways to simplify this process for property owners and provide flexibility to meet the needs of the City’s diverse housing types and households, while ensuring new homes fit in with their neighbors. As part of this effort, the City is assessing parking regulations to determine the right requirements for single-family properties, studying similar cities to understand how they have made it easier to build and adapt homes, and learning from the public about what they want when it comes to site design, public noticing, special cases and exceptions, and how to treat special uses and neighborhood-serving commercial uses.
Overview of Key Issue Topic
As a result of recent state laws and regulations, jurisdictions must comply with statewide housing legislation which focuses on reducing constraints for housing development across different zoning districts and streamlining review of housing. Jurisdictions are required to comply with state housing law, which is implemented through local Zoning Codes. Single-family residential (SFR) regulations that are clear and well-designed are important for building context-sensitive neighborhoods and providing diverse housing types.
Adopting Zoning Code regulations based on the current environment and future community goals can lead to the development of new housing opportunities while being designed to blend in with the visual and social fabric of existing neighborhoods. Incorporating development standards, such as building height, setbacks, and lot sizes, that are sensitive to the existing community can help ensure new housing is compatible with the surrounding environment. At the same time, adopting development standards that reflect recent state laws provides property owners opportunities to develop a greater variety of housing types on their own lots to increase the housing supply for family, caregivers, and individuals seeking rental opportunities.
In addition to the development standards in SFR neighborhoods, adopting clear and appropriate administration and procedural requirements for the Planning Application review process helps streamline the approval process for owners seeking additions, remodels and/or new construction.
When the process for developing single-family homes is clear and easy-to-use, the cost of projects typically decreases and projects are approved faster, benefiting the property owners, residents, and the City alike as this can support increased homeowner investment in their neighborhoods. Well-written SFR regulations ensure compliance with state law requirements, promote community growth, and help provide a framework to streamline development while aligning with neighborhood priorities.
Brief Summary of Current Title 27 (Zoning) Regulations
In the current Zoning Code, Chapter 27.18 (R1 Districts – One Family Dwellings) establishes regulations for SFR development within the R1 District. Chapter 27.18 outlines the purpose of this District, permitted and special uses, and development standard regulations. The Chapter provides standards for January 22, 2026 | Page 3
SFR development including, but not limited to, building height and daylight plane, parcel size standards, floor area ratio, and setbacks and exceptions to setbacks (i.e., encroachments).
This Chapter also contains the following development regulations unique to the City’s Zoning Code for SFR projects, organized under the following sections:
• Section 27.18.035 (Substantial Removal of Existing Residence): This Section states that a Special Use Permit is required for the substantial removal of an existing residence without a change in use. This Section also outlines related requirements and exemptions. • Section 27.18.115 (San Mateo Park Planning Area): This Section provides setback regulations for the San Mateo Park Planning Area, which requires new residential products to be built at a deeper setback than allowed in other areas of San Mateo.
The City also adopted the “Single-Family Dwelling Design Guidelines” in 2001, which were most recently revised in 2006. While these guidelines are required to apply to SFR projects through the Single-Family Dwelling Design Review (SFDDR) process per Section 27.08.032(b)(1), they exist as a standalone document that has not been codified in the SMMC. Because the guidelines are not written as objective design standards, often as considerations or suggestions rather than firm requirements, they can be difficult to interpret and enforce objectively, which may lead to inconsistencies in how requirements are applied to different projects.
General Plan’s Direction and Policies
This section provides the General Plan 2040 policies and action that will be considered and taken into account when drafting the updated SFR regulations in the SMMC.
Policy LU 3.1 - Housing Diversity
Policy LU 3.1, Housing Diversity, directs the City to “promote safe, attractive, and walkable residential neighborhoods with diverse types and sizes of homes for individuals, families, and households of all income levels.”
To address this policy, the CZCU will establish clear and objective development and design standards for housing projects for a variety of types and sizes, to meet the needs of households of all income levels in San Mateo. Additionally, the City will review and revise the permitted housing types to encourage innovative and flexible housing opportunities.
Policy CD 7.1 - Low-Density Residential Development
Policy CD 7.1, Low Density Residential Development, directs the City to require new homes in the Lowand Very Low-Density residential zoning district (i.e., single-family dwellings, duplexes, triplexes, fourplexes, and ADUs) to be consistent with the objective design standards outlined in the City’s Residential Design Standards.
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To address this policy, since these design guidelines are overall subjective in nature, the City will need to adopt new objective design standards for single-family development in San Mateo. However, the adoption of these new standards will occur after the completion of the CZCU. Until the new regulations are adopted, the City will maintain the current practice of referencing and applying the existing design guidelines document.
Policy CD 7.2 - Single-Family Design
Policy CD 7.2, Single Family Design, directs the City to “encourage single-family additions and new dwellings that address the preservation and enhancement of neighborhood visual and architectural character through context-sensitive building scale, materials, architectural style and details, and privacy.”
To address this policy, the CZCU will include clear and balanced development and design standards for SFR projects that consider the various neighborhood contexts of San Mateo. While these standards will consider the City’s existing architectural design, they will also recognize that high-quality, contextsensitive design does not always equate to maintaining the existing architectural style of a neighborhood. In some San Mateo neighborhoods, such as those with primarily post-war ranch homes, a variety of architectural styles may result in a better neighborhood design. In others, deviation from more traditional architectural styles could be accomplished by using modern materials and incorporating similar proportions and roof forms. Together, the CZCU will support both cohesive and diverse architectural design styles to ensure flexibility for innovative design styles when determining the development and design regulations for SFR districts. As discussed above in Policy CD 7.1, while there will be some design standards in the Zoning Code, single-family design will primarily be addressed through the development of objective design standards, which is planned to happen after the adoption of the CZCU.
State Law Compliance
SB 9 (Chapter 162, Statutes of 2021) requires jurisdictions to ministerially approve either up to two primary dwelling units on a parcel in a single-family zone (i.e., two-unit housing developments), the subdivision of a single parcel into two parcels (i.e., urban lot splits), or both. In 2022, the City adopted a new Two-Unit Development Residential Overlay District (Chapter 27.21). Since this Chapter has been recently updated, the CZCU process will not be updating the City’s SB 9 regulations.
SB 1123 (Chapter 294, Statutes of 2024) expands upon SB 684 (2023) to further streamline the development of small-scale infill housing projects in SFR zones. SB 684 streamlined approvals for infill developments of up to 10 homes on vacant lots in multi-family residential districts. SB 1123 extends the provisions of SB 684 to allow construction of up to 10 homes on qualifying single-family parcels near commercial zones, schools, transit, and other amenities. The CZCU will assess how other jurisdictions have incorporated regulations to address SB 1123 and determine how to best apply these new regulations in the CZCU.
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Additionally, the City’s current parking requirements for SFR uses need to be further reviewed and updated in accordance with recent state legislation. This includes Assembly Bill (AB) 2097 (2022), which generally restricts jurisdictions from imposing minimum parking requirements for residential, commercial, and certain other development types within one-half mile of a major transit stop.
Best Practice Options and Considerations
This section outlines best practices and key considerations drawn from City staff input, state guidance, and comparable jurisdictions. The Project Team reviewed best practices from comparable jurisdictions to ensure the updated regulations reflect current planning standards successfully applied in comparable communities. These references help identify approaches that are clear, consistent, and adaptable to San Mateo’s goals and current built environment. The comparable jurisdictions referenced in this white paper include the cities of Milpitas, Sacramento, and Stockton. • Milpitas was chosen because it was just comprehensively updated in 2025, the city has a similar built environment to San Mateo and is located nearby, and the code includes clear writing and consistent organization.
• Sacramento was chosen because it was seen as a good example by city staff and contains a detailed list of administrative and permit processes and procedures. • Stockton was chosen because it was just comprehensively updated in 2025, the use regulations and development standards are clear and well-written, and there are detailed and easy-to-use site development and specific to use regulations.
The following considerations will help inform how to update the City’s SFR regulations:
• As discussed in the “Brief Summary of Current Title 27 (Zoning) Regulations” above, Section
27.18.035 (Substantial Removal of Existing Residence) states that a Special Use Permit is required for the substantial removal of a residence that does not change the use of the structure. However, if the City decides to retain the Single Family Dwelling Design Review (SFDDR) process, substantial removals and remodel should be identified as a rebuild or a new single-family residence to establish a clear expectation for which project is subject to the process. The CZCU will also evaluate whether to remove planning application level review for substantial removal of walls or roofs if no second-story addition is proposed because singlestory detached residences on stand-alone lots typically generate little, if any, controversy, particularly when designed in compliance with the current design guidelines and forthcoming objective design standards. Additionally, if an existing residence does not currently comply with all development standards, the CZCU process will clarify if substantial removal of a residence requires the proposed building to fully conform to all current development standards (i.e., if the existing building is non-conforming to any development standards) or if a substantial removal shall require an applicant to rebuild the subject development. • The current Zoning Code outlines identical requirements of limits on front paving setback areas in Sections 27.18.070(d) (Front Yard) and 27.18.080(b)(4) (Side Yards). The CZCU process will determine how to combine these regulations under one section to be written more January 22, 2026 | Page 6
clearly and reflect how comparable jurisdictions organize similar regulations. Additionally, these sections do not provide specific landscaping and vegetation requirements within heavily paved areas. The CZCU will establish requirements that set a maximum amount of impervious surface allowed in front yards that applies equally to walkways and driveways. It will also consider setting a minimum amount of impervious surface needed to access garages and building entrances, particularly on narrow lots where access is challenging. This approach would give residents flexibility in how they allocate their allowed impervious surface allotment. Furthermore, it would specifically support senior residents by providing additional paved area to address walking and accessibility concerns, such as connecting ramps into existing homes. In addition, the CZCU will evaluate options for accommodating additional offstreet parking on paved areas in situations where AB 2097 limits parking requirements and when garages are converted to ADUs or JADUs.
• Section 27.18.080 (Side Yards) and Section 27.18.070(b) (Garage Setback) require a minimum of a 20-foot setback for garages on street side yards and front yards. The CZCU process will evaluate if this requirement should be retained. Some other jurisdictions, such as the City of Milpitas and the City of Sacramento, do not provide additional requirements for setbacks or garages on street side yards and front yards, while the City of Stockton does also require a minimum of 20-foot setback.
• The City will consider if projects proposing extensions of walls within nonconforming side yards should still follow the Site Plan and Architectural Review (SPAR) process as required in Section 27.18.080(c)(4). Although comparable jurisdictions also require a site plan and architectural review process for the extensions or expansions of nonconforming features in SFR zoning districts, the SMMC also includes the SFDDR process. The SFDDR should be evaluated to determine if this process is a better option for SFR projects with proposed extensions of nonconforming walls within side yards.
• The CZCU will determine how to update the parking requirements in Section 27.18.110 (OffStreet Parking) related to single-family development. For example, allowing tandem parking for SFR developments, making covered parking requirements more flexible, assessing the number of parking stalls required for larger homes, and looking at ways to incentivize offstreet parking in areas where parking requirements cannot be enforced. • The CZCU will review all single-family setback requirements (front, side and rear) to assess how San Mateo’s requirements compare with other similar jurisdictions and if any changes or updates are warranted.
• To support General Plan Policy CD 7.2, Single-Family Design, the City will be looking at a future effort to convert the single-family design guidelines into objective design standards (ODS). For the most part, the Zoning Code will not include architectural design standards; however, the Code does have the ability to support design objectives, and to that extent, the CZCU will be assessing opportunities for appropriate inclusion of requirements to support single-family design goals.
• The SMMC does not currently have provisions that address requirements for double frontage or through lots. Comparable jurisdictions such as the City of Milpitas and the City of Stockton January 22, 2026 | Page 7
include a description of front lot lines for through lots in the definitions section. The CZCU will adopt a similar approach to incorporate the definition for double frontage or through lots. • The SMMC currently provides very limited regulations that address irregularly shaped lots.
Chapter 27.21 (Two-Unit Development Residential Overlay District – R1 Districts), which provides the City’s regulations to comply with SB 9 requiring jurisdictions to allow two-unit developments and urban lot splits in low-density residential districts, includes a definition for flag or panhandle lots (Section 27.21.020(f)) and incorporates minimum width requirements for access strips or easements for flag lots and landlocked parcels created through urban lot splits. Except for these regulations, the SMMC does not include standards that address irregularly shaped lots for the purposes of ensuring consistent and compatible development patterns, preserving the existing building configurations, and avoiding access issues as a result of atypical lot shapes. Comparable jurisdictions such as the City of Milpitas and the City of Stockton allow the Director to determine lot depth, width, and setbacks for irregularly shaped lots in the definitions or Rules of Measurement sections. The CZCU will take a similar approach to incorporate regulations for irregularly shaped lots. • Small lots that do not meet current minimum lot requirements in the SMMC can pose challenges for development potential, nonconforming status, and consistency with existing neighborhood context. To address this issue, the CZCU will further research pathways to accommodate those parcels.
• The permitted and special uses in the R1 District contain outdated use names (e.g., sanitariums) and regulations that apply to specific types of uses, such as the regulations for cemeteries, mausoleums, and columbaria (Section 27.18.120). The CZCU will add categories of uses (e.g., residential, commercial, industrial) to organize permitted and special uses to be easier to apply, reflect current practices, comply with state law, and provide regulations for specific uses allowed in that may benefit from additional development and operational standards.
• The City has extensive noticing requirements which exceed state requirements and those of other comparable jurisdictions around the Bay Area. Redwood City follows state requirements (see the “State Law Compliance” section of the Public Noticing white paper for details on recent legislative changes) with the exception of additional requirements for the Downtown Specific Plan. Sunnyvale sends out notices to property owners with 300 feet. By comparison the City of San Mateo requires notice to property owners and tenants within a radius of up to 500 feet from the project site. There is a significant cost to the distribution of these notices, which limits residents’ ability to invest in their homes and neighborhoods. The CZCU will assess and recommend updates to the City’s notification requirements, in particular for single-family projects, to reduce cost burdens and better align with best practices while being mindful of community outreach expectations.
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Potential Questions for Public Input
• How should the City manage garage setbacks (the required distance between a garage and the property line) for front and exterior side yards in single-family residential areas? (Select all that apply.):
o Maintain the current setback requirements
o Decrease the required setbacks for garages
o Allow reductions for specific cases (e.g., narrow lots, alley access, design compatibility)
o Not sure/ No opinion
o Other (Please specify.):
• How should the fence height requirements for single-family properties be updated? (Select all that apply.)
o Maintain existing fence height limits
o Allow taller fences in side or rear yards
o Allow greater fence height along street frontages with design standards o Require setbacks or landscaping for taller fences
o Allow reductions for specific cases (e.g., narrow lots, alley access, design compatibility)
o Other (Please specify.):
• What types of single-family projects should the City continue to require public noticing for? (Select all that apply.):
o New one-story single-family residence
o Existing residence alteration with a Special Use Permit o Second story addition of 200 square feet floor area or greater to a single-family residence, if it is not a substantial removal of existing residence o New two-story single-family residence or existing residence alteration with a Special Use Permit
o Alteration, addition, or demolition of a single-family residence designated as historic resource, eligible for historic designation, or located in historic districts o All of the above
o None of the above
• When a single-family home project requires a public notice, how far from the property line should the City and applicants be required to notify neighbors?:
o Adjacent properties only
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o Properties within 100 feet
o Properties within 200 feet
o Properties within 300 feet
o Not sure/ No opinion
o Other (Please specify.):
• Which of the following design features or architectural elements best reflect the character of San Mateo’s single-family neighborhoods?:
o Varied rooflines and building heights
o Front porches or covered entryways
o Use of natural materials (e.g., wood, stone, stucco)
o Well-landscaped front yards
o Detached garages or driveways with landscaped setbacks o Large front or bay windows
o Other (Please specify.)
• Which of the following design standards should the City adopt, if any, to regulate the visibility of garage doors along the street frontage? (Select all that apply.):
o Require the garage door to be setback a minimum distance from the front of the house
o Limit the percent of the front facade that a garage door can occupy o Limit the width and height of the garage door
o Require the use of similar materials and architectural detail of the primary dwelling o Require the garage to be accessed from a side street or alley when possible o Other (Please specify.):
• Would you like to see neighborhood-oriented, small-scale commercial uses (such as cafés or small markets) allowed in single-family residential areas? o Yes, they would make neighborhoods more walkable and convenient o Maybe, but it depends on the type of commercial use and/or only if carefully designed and limited in size and hours
o No, single-family areas should remain strictly residential o Not sure / No opinion
• Should tandem parking (where one car parks directly behind another in a driveway or garage) be allowed in single-family residential developments?
o Yes, tandem parking provides flexibility and helps reduce driveway widths o Maybe, but only for certain lot sizes or situations
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o No, it’s inconvenient and can block access for residents of the property o Not sure / No opinion
• What types of exceptions to the required setbacks are acceptable? For instance, do you think a neighbor should be allowed to build a deck, balcony, trellis/arbor, or outdoor kitchen in a required side yard? Should a neighbor be able to install a greenhouse window or bay window projecting into the yard and by how much?
• What SFR requirements do you think are most important to maintain? Are there any requirements that you think should be changed or removed?