Local zoning · San Mateo

San Mateo — Development Standards

Q: What are San Mateo setback requirements for single‑family homes?

Base single‑family setbacks are: front yard 15 ft , street‑side setbacks are a percentage of lot width with minimums (for corner lots), typical rear yard 15 ft (or 25 ft when above one story). See § 27.22.070 , § 27.18. * and § 27.18.090 for full rules.

Q: How do ADUs affect FAR calculations?

San Mateo allows up to 800 sf of ADU living area to be exempt from the lot's maximum FAR in many single‑family situations (state‑exempt ADUs), but ADUs over 800 sf are subject to the underlying district’s FAR. Conversion ADUs have different rules. See § 27.19.060 for the ADU size, FAR, and utility fee rules.

Development Standards under the San Mateo local zoning and planning code, with the controlling citations.

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Last reviewed: July 2, 2026

Overview

This page summarizes the San Mateo Municipal Code (Title 27) rules that control development setbacks, height, lot coverage, density, and FAR across the City's zoning districts and overlays. It synthesizes the code's objective dimensional standards and where they live in the ordinance so designers and applicants can quickly find the controlling sections and next steps. Where the code delegates to another plan (for example, the Building Height Plan or Downtown Specific Plan) that is noted and cited; parcel‑level confirmation is required for site-specific projects.

Key first links: the City’s Zoning overview, and standards or processes that commonly apply to development projects such as parking, design review, overlay districts, and ADUs. State technical compliance remains with the California Building Standards Code.

Quick reference table — decision‑relevant numeric standards

This table highlights the most commonly checked numeric limits. Always verify parcel‑specific standards (some areas are governed by the General Plan Building Height Plan or a Specific Plan).

District / Standard	Typical front setback	Side / street‑side	Rear yard	Max FAR / Lot coverage / Units	Governing code cite
R‑1 (single‑family)	15 ft (minimum)	street‑side: 15% lot width / other side rules per R1-B	15 ft (25 ft for >1 story)	Underlying R district standards; see applicable R1 chapter	Front yards § 27.22.070; street‑side rules § 27.18.*
R‑2 (two‑family)	See R1 rules; multiple‑family front setback rules apply	Side yard rules reference R1‑B; see § 27.20.070	Rear yards per R1/R2 rules	Typical FAR 0.6 (varies by neighborhood: 0.5 / 0.6)	FAR § 27.20.060; special neighborhood limits § 27.20.065
R‑3 / R (multi‑family moderate)	Front yards: 15 ft; multi‑family exceptions apply	Side yards: 6 ft for 1–2 story; taller = 1/2 building height (max 25 ft)	Rear yards: 15 ft (25 ft for >1 story)	Floor area and density per district; building height per General Plan	Yards § 27.22.070–27.22.090; building height § 27.22.055
R‑4 / R‑5 / R4‑D / R5‑D (higher density)	Varies; some standards defer to R3	Minimum parcel/density tables in code	Often larger rear yards in D variants	R4 FAR 1.5 (may be up to 2.0 by permit); R5 can go to 2.0–3.0 or special approvals; density caps (often 50 u/ac)	FAR § 27.24.050, R5 allowances § 27.26.020, density caps § 27.29.106
R6‑D (high density)	Front yard 20 ft	Side yard 15 ft	Rear yard 25 ft	Max coverage 55%, Max FAR 3.0, max 50 u/ac	Yard & bulk § 27.28.084–27.28.088; coverage § 27.28.078; FAR § 27.28.080
CBD / Downtown (Central Business District)	Many parcels built to property line; special build‑to/retail frontage rules	Buffers required next to R zones (depth = 1/2 building height or 15 ft whichever greater)	Special rear yard rules in Downtown Specific Plan	FAR and heights track Downtown Plan / Building Intensity Plan; residential density often ≤ 50 u/ac	Build‑to and frontage rules § 27.38.100–27.38.110; buffer § 27.38.130; Downtown gateway rules § 27.28.053
C1 / Neighborhood commercial	Buffer/setback where adjacent to residences (often match residential setback)	Side/rear buffer requirements when next to R zones	Rear yards when adjacent to R zones per buffer tables	FAR varies by C1 subtype (C1‑.5 0.5, C1‑1 1.0, up to 3.0 in C1‑3)	Permitted uses & FAR table § 27.30.010, § 27.30.050; buffers § 27.30.060
C4 / General commercial	El Camino Real build‑to and setback standards apply	Buffers like C1; specific El Camino Real standards	See C4 and El Camino Real rules	FAR per C4 subtype (e.g., C4‑.5 0.5, C4‑1 1.0, C4‑1.5 1.5)	FAR and El Camino Real rules § 27.36. (see § 27.36.055)
Two‑Unit / SB9 overlay (R1 areas)	Underlying front setback applies; side & rear 4 ft minimum for SB9 units	SB9 height caps: attached 24 ft plateline (32 ft peak), detached 16 ft plateline (24 ft peak)	Side/rear: 4 ft for new SB9 units; conversions may be exempt	SB9 references underlying district FAR; limited exemptions up to 800 sf unit and objective standards	Two‑unit / SB9 standards § 27.21.010–27.21.070 (see demolition, setbacks, height, parking)

Notes: numeric values in bold above are pulled directly from the Municipal Code. Many height limits defer to the City's General Plan Building Height Plan rather than a single numeric maximum — see §§ 27.22.055, 27.24.055, 27.30.055 and district‑specific building height sections.

District‑by‑district guidance (purpose, typical uses, and the key dimensional controls)

R‑1 (Single‑Family Residential)

Purpose & where it applies: single‑family neighborhoods; the code intends low‑intensity residential character. See the R1 chapters for subvariants (R1‑A, R1‑B, R1‑C).
Typical permitted uses: single‑family dwellings and limited accessory uses; special permits required for substantial removals or certain plumbing in accessory buildings. See Chapter 27.18 for permitted uses and special permits.
Key dimensional controls: front yard 15 ft (§ 27.22.070), street side setback percentages and minimums (for corner lots; e.g., 15% of lot width, min 7.5 ft, different caps in subsections) (§ 27.18.* and § 27.18. respectively) and rear yard 15 ft (25 ft where new construction is above one story) (§ 27.18.090) .
Practical note: historic/heritage trees, front‑yard paving limits, and driveway width standards are enforced in R‑1—plan to show landscaping and driveway layout. See the street side yard paving and driveway width rules in § 27.18. .

R‑2 (Two‑Family)

Purpose: allow duplexes while largely following R‑1 yard and height rules; some parcel‑based FAR limits apply.
Dimensional highlights: R‑2 frequently borrows R‑1 yard rules (§ 27.20.070), but FAR in many R‑2 neighborhoods is 0.6 (with local exceptions 0.5/0.6 for mapped neighborhoods) (§ 27.20.060, § 27.20.065) .

R‑3 / R (Multi‑Family, Moderate)

Purpose: medium‑density multifamily. Uses include apartments and duplexes; subject to yard and daylight plane rules.
Key standards: front yard 15 ft (exceptions exist), side yards for 1–2 story units 6 ft, taller buildings require side yard equal to 1/2 building height up to 25 ft (§ 27.22.080), building height is controlled by the General Plan Building Height Plan (§ 27.22.055) .

R‑4 / R‑5 (Higher density multi‑family)

Purpose: higher density residential with options for special permits to increase FAR and bulk. Density tables and minimum parcel sizes appear in the district chapters.
Key numbers: R4 base FAR 1.5 (administrative permission may allow up to 2.0 with findings) (§ 27.24.050). R5 allows higher FAR/density up to 3.0 with special use approvals and often cites 50 units per acre caps in overlays (§ 27.24.050, § 27.26.020, § 27.29.106) .

R6‑D (High density residential district)

Purpose: highest‑density residential areas, often with planned unit configurations.
Standards you must check: front yard 20 ft, side yard 15 ft, rear yard 25 ft, max parcel coverage 55%, max FAR 3.0, maximum 50 units per acre (§ 27.28.084–27.28.090, 27.28.078, 27.28.080, § 27.28.076) .

CBD (Central Business District) and Downtown Specific Plan areas

Purpose: prioritized pedestrian retail frontage at ground floor, active downtown uses, and concentrated development intensity. CBD rules promote build‑to frontage and ground‑floor retail standards.
Dimensional regime: many parcels are required to build to the property line to a minimum height (e.g., 26 ft street wall in some areas) or follow the Downtown Plan build‑to and street wall rules (§ 27.38.100, § 27.38.110, § 27.38.130). The Downtown Specific Plan and Gateway Area impose special setbacks, step‑backs, and yard requirements (see the Gateway table in § 27.28.053) .
Practical note: downtown projects must check required retail frontage blocks and may be eligible for Downtown Economic Development exceptions if they meet findings (§ 27.38.140) .

C1 / C4 (Commercial)

Purpose: neighborhood and general commercial uses; compatibility buffers where commercial abuts residential.
Controls: C1 FAR varies by subtype (C1‑.5 = 0.5, C1‑1 = 1.0, up to C1‑3 = 3.0) (§ 27.30.050). When abutting residential zones, the commercial parcel must provide buffers/setbacks matching the residential standards or the most restrictive applicable requirement (§ 27.30.060, § 27.30.040). .

Two‑Unit Development Overlay / SB9 (applies to qualifying R1 parcels)

Purpose: to implement state SB 9 allowance for up to two primary units and urban lot splits while preserving objective local standards. See Chapter 27.21 for the overlay standards.
Key objective standards: side & rear setbacks for new SB9 units 4 ft minimum; height caps for SB9 units (attached 24 ft plateline / 32 ft peak; detached 16 ft plateline / 24 ft peak); parking one space per SB9 unit unless exempt based on transit/accommodations (§ 27.21.070 and related subsections) .
Practical note: SB9 units still must meet the objective standards of the underlying zone; conversions of existing legally permitted structures may be exempt from setbacks (§ 27.21.070(d)(3)) .

ADUs (Accessory Dwelling Units)

ADU rules alter typical FAR and size rules in single‑family zones: up to 800 sf of ADU living area can be exempt from the lot's FAR allowance (subject to other limits); an ADU cannot be larger than the primary dwelling except limited state exemptions; consult § 27.19.060 for single‑family ADU specifics. For project design, check utility, fee, and address requirements in the ADU chapter. Link: ADUs.

Checklist (what an applicant must satisfy for a typical residential or mixed‑use project)

Confirm zoning district and all applicable overlay districts for the parcel (e.g., Downtown Specific Plan, Two‑Unit Overlay). Verify plan maps. (§ 27.29. and specific overlay chapters)
Demonstrate compliance with front, side, street‑side and rear yard minima from the applicable district (§ 27.22.070–27.22.090, or district chapter cited above)
Show maximum FAR, lot coverage and density limits and how the proposal fits; if in an R4/R5/R6‑D or CBD, confirm FAR caps in district chapter and any overlay § (e.g., § 27.24.050, § 27.28.080).
Confirm building height limit(s) by district and by the General Plan Building Height Plan where cited (§ 27.22.055, § 27.24.055, § 27.30.055)
Provide required parking calculations and demonstrate conformance with Chapter 27.64 (see parking) and any SB9 exemptions (§ 27.21.070).
If project triggers design review or discretionary review (SPAR, SFDDR, Planning Commission), include required design materials (see design review and § 27.08.030)
For ADUs, follow ADU chapter size, parking, and utility rules in § 27.19.060 and reconcile with FAR limits (ADU exemptions up to 800 sf)
Check for required buffers/landscaping where commercial abuts residential (see landscaping and screening and § 27.30.060, § 27.38.130)
For technical building, life‑safety, and accessibility compliance use the California Building Standards Code — Title 27 does not replace Title 24 compliance. (Note: building‑code specifics are outside Title 27; see § references where Title 27 defers to building codes)

Risks & Ambiguities

Issue	Why it matters	What to verify
Reliance on the General Plan Building Height Plan	Many district sections defer to the Building Height Plan rather than giving a single number; an application can be rejected for exceeding that plan even if it seems within a district's typical range	Verify the parcel on the City's Building Height Plan map and cite § 27.22.055, § 27.24.055, § 27.30.055
Downtown Specific Plan / Gateway exceptions	Downtown/Gateway has separate yard and step‑back rules that override base district yards and heights	Confirm whether the parcel falls inside the Downtown Specific Plan boundary and apply § 27.28.053 and related Downtown chapters
Overlay / Qualified (Q) district conditions	Q districts (Q6, Q7, Q8, etc.) may impose unique FAR, use restrictions, or required master plans	Check overlay text for site‑specific FAR and required permits (examples in § 27.60 and overlay subsections cited in district chapters)
SB9 vs. existing non‑conforming structures	SB9 allows smaller setbacks for new units, but conversions of existing legal structures may be exempt; misunderstanding can lead to permit denial	For SB9 projects, apply §§ 27.21.010–27.21.070 and confirm conversion vs new construction rules and demolition limits
ADU FAR & coverage exemptions	ADU exemptions (e.g., up to 800 sf exempt from FAR) interact with underlying FAR differently depending on whether the ADU is a conversion, attached, or new detached unit	Check § 27.19.060 for ADU size/FAR rules and whether the project qualifies as a Conversion ADU or State Exempt ADU

Plain‑English summary

San Mateo's Title 27 sets numeric setbacks (front, side, rear), ranges or caps for floor‑area ratio and lot coverage, and directs many height questions to the City's Building Height Plan or to specific area plans like the Downtown Specific Plan; special overlays (including the SB9 two‑unit overlay) add or change a few objective rules (for example, SB9's 4‑ft side/rear setback and specified SB9 height caps). Always check the code section cited for your district and overlays and confirm the parcel against the City maps. (§ 27.22.070, § 27.21.070, § 27.28.080)

Information Gaps

Exact numeric height limits for many zones are not given as single numbers in the retrieved materials; the code repeatedly defers to the Building Height Plan of the General Plan. Confirm parcel‑specific height maxima on the Building Height Plan. (§ 27.22.055, § 27.24.055, § 27.30.055)
Some zone subtypes and Q overlays (Q6/Q7/Q8) reference master plans or prior Planning approvals for their exact FAR and permitted uses; the full text of those master plans and Planning Application files is not in the retrieved code excerpts. See each Q district subsection for site‑specific limits (§ 27.60 and overlay subsections).
Where the code references maps (Building Height Plan, Downtown Plan maps), those maps were not included here — verify parcel mapping with the Planning Department. Not found in retrieved materials: the physical maps themselves.

Source References

San Mateo Municipal Code, Title 27 — Front/side/rear yard and general district rules: § 27.22.060–27.22.090
Two‑Unit Development / SB9 overlay: § 27.21.010–27.21.070 (standards: demolition, setbacks, height, parking)
R‑2 FAR and yard rules: § 27.20.060, § 27.20.065 (neighborhood variations)
R3/R4/R5 district FAR and development standards: § 27.24.050, § 27.26.020, § 27.29.110 (residential overlay provisions)
R6‑D district coverage, FAR, yards: § 27.28.076–27.28.090, § 27.28.078, § 27.28.080
CBD/Downtown rules, build‑to and retail frontage: § 27.38.100–27.38.140, Downtown Gateway yard/height table § 27.28.053
C1 district permitted uses, buffers, FAR: § 27.30.010, § 27.30.050, § 27.30.060
ADU development standards (single‑family ADUs): § 27.19.060 (size, FAR interactions, utilities)
Off‑street parking references and SB9 parking exemptions: § 27.64 referenced in SB9 chapter and § 27.21.070(e) (see parking exemptions for transit proximity)
City administrative & review authority (Zoning Administrator, SPAR, SFDDR, variances): § 27.08.030 and § 27.90.030–27.90.050 for plan areas and administrative processes

Sources

Retrieved passages

San Mateo Zoning Code (Article II) High relevance
San Mateo Zoning Code (§ 2) High relevance
San Mateo Zoning Code (Chapter 27.40) High relevance
San Mateo Zoning Code (§ 9) High relevance
San Mateo Zoning Code (Section 27.08.030) High relevance
San Mateo Zoning Code (section shall) High relevance
San Mateo Zoning Code (Section 27.24.040) High relevance
San Mateo Zoning Code (Chapter 5) High relevance

Cited sections

Official San Mateo code library

Frequently asked questions

What can I build on an R‑1 lot in San Mateo?

You can build uses allowed in the R‑1 district (primarily a single‑family dwelling and accessory uses); dimensional controls include a 15 ft minimum front yard, street‑side setback rules (percent of lot width and minimums), and a 15 ft rear yard (increased to 25 ft for new construction above one story). Always check Chapter 27.18 and yard rules in §§ 27.22.070–27.22.090 for subdistrict variations and special permits.

What are San Mateo setback requirements for single‑family homes?

Base single‑family setbacks are: front yard 15 ft, street‑side setbacks are a percentage of lot width with minimums (for corner lots), typical rear yard 15 ft (or 25 ft when above one story). See § 27.22.070, § 27.18.* and § 27.18.090 for full rules.

How is building height determined in San Mateo?

Height is often governed by the City’s Building Height Plan referenced throughout Title 27; district chapters reiterate that building height “shall not exceed the standards set forth on the Building Height Plan of the General Plan” (see §§ 27.22.055, 27.24.055, 27.30.055). Confirm the parcel on the Building Height Plan map for the numeric limit.

What are the lot coverage and FAR limits I must check?

FAR and coverage depend on district: for example R4 base FAR 1.5 (§ 27.24.050), R6‑D max FAR 3.0 and coverage 55% (§ 27.28.080, § 27.28.078), and C1/C4 have subtype FAR tables (e.g., C1‑.5 = 0.5, C1‑1 = 1.0) (§ 27.30.050, § 27.36.). Check the district chapter and any overlay Q district text.

Do SB9 / Two‑Unit Overlay projects have different setbacks and height rules?

Yes. The Two‑Unit Development (SB9) overlay establishes objective standards: new SB9 units generally must have 4 ft side and rear setbacks (front setback follows the underlying zone); SB9 height caps for attached units are 24 ft plateline (32 ft peak) and for detached units 16 ft plateline (24 ft peak). Parking rules and conversion exceptions are in the SB9 article. See § 27.21.070 and the Two‑Unit chapter.

How do ADUs affect FAR calculations?

San Mateo allows up to 800 sf of ADU living area to be exempt from the lot's maximum FAR in many single‑family situations (state‑exempt ADUs), but ADUs over 800 sf are subject to the underlying district’s FAR. Conversion ADUs have different rules. See § 27.19.060 for the ADU size, FAR, and utility fee rules.

Will I need design review for a multi‑unit or SB9 project?

Potentially. The Zoning Administrator and Planning Department have authority for SFDDR, SPAR, and other reviews depending on unit count, objective design‑standards compliance, and whether the project meets discretionary triggers (§ 27.08.030). Check design review and the Zoning Administrator's delegated authority.

When does commercial development need a buffer next to residences?

When a C district parcel adjoins an R district, buffers and setback equivalents are required: the depth of buffer along interior lot lines is at least one‑half the building height or 15 ft, whichever is greater; other buffer rules and required fences/walls are in the CBD/C1 sections (§ 27.38.130, § 27.30.060).

Are there special Downtown/Gateway yard or height rules I should know about?

Yes. The Downtown Specific Plan’s Gateway area specifies front yard build‑to and height bands (e.g., front setback 15–20 ft for a portion of frontage and minimum/maximum street wall heights; taller portions must be setback behind the primary facade) — see § 27.28.053 and associated Downtown chapters.

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