San Mateo County Zoning, Planning & Building Codes

Last reviewed: July 3, 2026

Overview

San Mateo County’s zoning for unincorporated areas is codified in the San Mateo County Ordinance Code as Title 8 — Zoning & Development Code (Part One, Division VI), which sets the countywide rules that apply only to unincorporated areas of the county and not to incorporated cities that adopt their own codes § 8.08.010 . The code is organized into Articles and Chapters that cover district definitions, development procedures, general development standards, special districts (PUDs/SS), overlays, and administration; common permit paths (ministerial vs. discretionary) are described in the development procedures chapters § 8.280.010 . Several specialized chapters implement statewide housing programs locally (Accessory Dwelling Units and the County Density Bonus program) and create overlay or special districts (Coastal Development § 8.252.010; Airport Overlay § 8.248.020) that layer additional standards on top of base zoning § 8.252.020 .

How San Mateo County's code is organized

• The zoning code is published as Title 8 — Zoning & Development Code and divides rules by Articles (e.g., Article 2 — Development Procedures; Article 3 — General Development Standards) and Chapters (e.g., Use Permits in § 8.280.010) § 8.280.010 .
• Districts and combining/overlay districts are listed and named in § 8.08.010 and § 8.08.020 (the official district table and combining-district rules) § 8.08.010 .
• Special zoning tools: Planned Unit Development (PUD) rules are in Chapter § 8.34.010 (PUD establishment and precise-plan process) and many PUDs appear as standalone ordinances that reference precise plans and conditions of approval § 8.34.010 .
• Topic chapters you will use often: parking standards (see § 8.344.030) and design review rules (see Chapter 8.256, referenced throughout PUDs and precise plans) § 8.344.030 .
• Administrative rules (fees, amendments, appeals) are in the zoning administration Articles (e.g., fees and amendments chapters such as § 8.440.010 and § 8.444.010) § 8.440.010 .

Practical navigation tip: start at § 8.08.010 (district list) to identify the base zoning for a parcel, then read the Article 2 chapters (use permits, variances, minor/major development) that apply to the requested action, then consult Article 3 and applicable overlay chapters for design/technical standards § 8.08.010 .

Zoning district families

San Mateo County’s base districts are enumerated in § 8.08.010; the county uses a broad family of residential, agricultural, commercial, industrial, and resource districts (table below lists the main district labels cited in the code) § 8.08.010 :

• Residential: R-E (Residential Estates), R-1 (One-Family), R-2 (Two-Family), R-3 (Multiple-Family), R-3-A (Affordable Housing), RH (Residential Hillside), RM (Resource Management as residential use allowed), and special purpose residential labels such as PC and R-1/CCP § 8.08.010 .
• Agricultural / Resource: A-1, A-2 (Exclusive Agriculture), A-3, PAD, TPZ (Timberland Preserve), TPZ-CZ (TPZ—Coastal Zone) § 8.08.010 ; TPZ has its own development/TM plan rules in Chapter 8.314 (DTM/TM Plan requirements) § 8.314.080 .
• Commercial & Office: O (Office), C-1 (Neighborhood Business), C-2 (General Commercial), coastal/shore-specific commercial such as CCR, and neighborhood variants like C-1/NFO § 8.08.010 .
• Industrial & Special: M-1 (Light Industrial), M-2 (Heavy Industrial), W (Waterfront), P (Parking district), plus Special Districts and Planned Special (SS and PUD) entries catalogued in Chapter 8.273/ § 8.273.010 § 8.273.010 .
• Overlay / Combining Districts: CD (Coastal Development District), A-O (Airport Overlay), and other combining districts are authorized and their regulations apply in addition to the base district rules § 8.252.010 .

(See the official district table at § 8.08.010 for the full list and combining districts § 8.08.020.) § 8.08.010

Citywide development standards

San Mateo County sets base development standards in the zoning chapters and in Article 3 (general development standards); many PUDs and specific-project ordinances then refine or substitute standards for particular sites.

• Setbacks, height, lot coverage, and floor-area rules: base districts specify typical uses and refer to district-specific setback/height limits; building height is defined and measured in the Zoning Ordinance § 8.04.030(52) and many PUDs and precise plans set heights and setbacks that "shall conform to approved plans" § 8.04.030(52) .
• Lot coverage and FAR: county practice is to reference district limits or precise-plan values; PUD and precise-plan ordinances repeatedly state that lot coverage and floor area shall conform to the approved plans (example PUD language) § 8.34.010 .
• Parking: off-street parking minimums and special rules live in the parking chapter; typical cross-references use § 8.344.030 for required parking ratios and exemptions § 8.344.030 . Link for practical info on local parking rules: San Mateo County Parking.
• Design review and objective design standards: design review (see Chapter 8.256 references) is required for many PUDs and precise-plan projects; PUDs explicitly require design review "pursuant to Chapter 8.256" and the Director has authority on minor plan conformance § 8.256 (referenced in PUDs) . Use the county design-review procedures page via San Mateo County Design Review.
• Sensitive-resource & hazard overlays: rules add site-specific standards (Primary Resource Areas / Scenic Corridor criteria, floodplain and seismic hazard design criteria) in the resource and hazard chapters (e.g., Primary Resource design criteria § 8.314.120; Special Hazard Area criteria § 8.314.130) § 8.314.120 .
• Where the code defers: many PUDs and precise-plan ordinances implement project-specific heights/ setbacks/parking on the approved plan rather than a single citywide numeric FAR or setback — read the PUD text and the implementing conditions because they often control over generic district rules § 8.34.010 .

Practical reading: after identifying a parcel’s base district, consult the district chapter, Article 3 general standards, any overlay chapter (e.g., CD § 8.252 or A-O § 8.248), and any PUD/SS/PRECISE-PLAN ordinance that lists site-specific controls § 8.08.010 .

• For countywide development standards guidance see San Mateo County Development Standards and the county’s design guidance text in design-review chapters § 8.256 .

Specific plans & overlays

• Planned Unit Development (PUD) districts: PUD districts are set out under Chapter 8.34 and individual PUD ordinances (e.g., PUD-128, PUD-129, PUD-134, etc.) contain precise plans, permitted uses, precise heights, setbacks, coverage, and unique operating/parking conditions; PUDs often require design review and other discretionary permits § 8.34.010 .
• Special Districts and Approved PUDs: Chapter 8.273 catalogs SS and PUD regulations and the code embeds many site-specific ordinances into the zoning text (see § 8.273.010 and the PUD entries) § 8.273.010 .
• Overlay districts that materially change allowable uses/conditions:
  • Coastal Development (CD) overlay: established for the Coastal Zone; CD applies in addition to underlying district rules and implements the California Coastal Act locally § 8.252.010–§ 8.252.030 .
  • Airport Overlay (A‑O): limits concentrations of people and can require use permits and acoustical analysis (interior CNEL standard) § 8.248.020–§ 8.248.060 .
  • Many other combining districts are listed in § 8.08.020 and described in their own subchapters § 8.08.020 .
• Where overlays or PUDs conflict with base rules, the site-specific PUD ordinance or the overlay chapter will specify which provisions govern; PUD language frequently states that "to the extent that the regulations contained herein conflict with other provisions of Part One, Division VI (Zoning), the regulations contained herein shall govern" § 8.34.010 .

Browse overlay summaries on the county’s overlay page San Mateo County Overlay Districts.

Building permits & review (how a project moves through the County)

• Permit tracks: the code distinguishes ministerial approvals (objective standards; e.g., many ADUs) from discretionary approvals (use permits, conditional use permits, major development reviews, PUD approvals) — see the Development Procedures chapters and Use Permit chapter § 8.280.010 .
• Typical sequence for a discretionary project: pre-application / environmental review (CEQA), design review (if required), public hearings on use permits or PUD amendments (Planning Commission/Board of Supervisors), then building and grading permits; PUDs and precise plans will list required approvals (design review, grading, coastal permits) before site disturbance § 8.34.010 .
• Minor versus major development: Timberland Preserve (TPZ) and other resource districts use separate minor/major development processes (e.g., Minor Development Permit § 8.314.060, Major Development Permit § 8.314.070) and DTM/TM plan requirements § 8.314.060–§ 8.314.080 .
• Appeals & administrative review: the Director of Planning and Building, the Zoning Hearing Officer, the Planning Commission, and ultimately the Board of Supervisors handle administrative decisions and appeals per the appeal chapters and the specific chapter for the permit type (appeals procedures appear in the use-permit and PUD language) § 8.280 .
• Building-code linkage: zoning approvals do not replace building permits; building-permit plan review enforces the County Building Regulations (Title 10) and state construction standards (California Building Standards Code / Title 24) — always obtain required building permits after zoning/entitlement approvals § 8.392.160 . See the statewide code reference: California Building Standards Code.

If you are an applicant: confirm whether your parcel sits in a base district, overlay, and/or a PUD (start with § 8.08.010), identify whether your project meets objective ministerial rules (e.g., ADU Chapter 8.392) or demands discretionary review (use permit / PUD), and then follow the steps in Article 2 (development procedures) and any PUD or overlay chapter that applies § 8.08.010 .

State housing law in San Mateo County

San Mateo County implements several State housing laws through dedicated chapters in Title 8 and cross-references to State law:

• ADUs / JADUs (ministerial path): the county has a dedicated ADU chapter — Chapter 8.392 (Accessory Dwelling Units) and Chapter 8.396 (Accessory Dwelling Units, Coastal Zone) — that allows ADUs in most residential districts, sets objective setbacks/height/parking rules, and requires ministerial approval for ADUs that meet the objective standards § 8.392.030–§ 8.392.050; § 8.396.010 . See the county ADU ministerial-approval rule: § 8.392.040 (ministerial approval without hearing) § 8.392.040 . Link with state ADU explanatory resources here: California ADU law.
  • Key local details: minimum side/rear setbacks may be 4 ft., ADU maximum height is 26 ft., at least an 800 sq. ft. attached ADU is permitted under certain conditions, and junior ADUs (JADUs) have separate smaller-size and owner-occupancy rules (see § 8.392.050, § 8.392.080) § 8.392.050–§ 8.392.080 . The county exempts many ADU features from lot-size/density limits as provided in the ADU chapter § 8.392.050 .
• Density bonus & inclusionary rules: San Mateo County implements State Density Bonus Law via Chapter 8.436 (Density Bonus) and provides local procedures for ministerial density-bonus determinations, concessions, and waivers § 8.436.010–§ 8.436.050 . The county’s inclusionary housing program and alternatives (in-lieu fees, off-site units) are in Chapter 8.432 § 8.432.040–§ 8.432.050 .
• SB 9 / lot splits / duplexes: specific SB 9 implementation language is not found in the retrieved Title 8 excerpts; confirm with County Planning staff or the ordinance codified after recent state changes — Not found in retrieved materials (verify with the County) (see County zoning amendments chapter § 8.444.010 for how changes are adopted) § 8.444.010 .
• Rent control / tenant protections: Title 8 is a zoning code and does not create countywide rent control in the unincorporated areas in the retrieved excerpts — Not found in retrieved materials; check separate county housing/tentant-protection ordinances or county/city-level measures for rent regulation (verify with County counsel).
• Interaction rules summary: where state law preempts or requires local action, the County’s chapters explicitly incorporate State law (e.g., § 8.436.030 confirms State Density Bonus Law controls where conflicts exist) § 8.436.030 .

For state housing-law overviews see California housing laws.

Quick-reference table (where to look first)

• "What is my base zoning?" — § 8.08.010 (District table)
• "Is an ADU ministerial?" — § 8.392.040 (ADU ministerial approval)
• "Parking standards" — § 8.344.030 (off‑street parking) San Mateo County Parking
• "PUD / precise-plan rules" — § 8.34.010 (PUD establishment & precise plan)
• "Coastal overlay" — § 8.252.010–§ 8.252.030 (CD district and its application)
• "Airport overlay" — § 8.248.020–§ 8.248.060 (A‑O intent, uses, acoustical requirements)
• "Density bonus" — § 8.436.010–§ 8.436.050 (County Density Bonus chapter)

Information Gaps / Things to verify with County staff

• SB 9 (lot-split/duplex ministerial ordinance language) is not present in the retrieved Title 8 excerpts — confirm whether the County has adopted SB 9 implementing regulations (Not found in retrieved materials) § 8.444.010 .
• Any recent amendments after the uploaded ordinance snapshot (e.g., ADU changes after 2024, SB 9 implementation, or local rent-protection measures) should be checked on the County code website or with the Planning & Building Department (check amendment chapter § 8.444.010 for how to track changes) § 8.444.010 .

Source References

• San Mateo County Ordinance Code, Title 8 — Zoning & Development Code; district designations and combining districts § 8.08.010, § 8.08.020 .
• Planned Unit Development rules and PUD precise-plan language § 8.34.010 and multiple PUD ordinances (PUD-128, PUD-129, etc.) .
• Use permits / development procedures: Article 2, Chapter 8.280 (Use Permits) § 8.280.010 .
• ADU rules: Chapter 8.392 (ADUs general) and Chapter 8.396 (ADUs, Coastal Zone) — approval, setbacks, JADU rules § 8.392.030–§ 8.392.050; § 8.392.080; § 8.396.010 .
• Density bonus: Chapter 8.436 (Density Bonus) including ministerial approval and bonus calculation § 8.436.010–§ 8.436.050 .
• Overlays: Coastal Development § 8.252.010–§ 8.252.030 and Airport Overlay § 8.248.020–§ 8.248.060 .
• Parking cross-references and examples in PUDs: see § 8.344.030 and PUD ordinances (examples describing minimum parking in project approvals) § 8.344.030 .
• Design review cross-references: Chapter 8.256 referenced throughout PUDs and precise plans for required design-review processes § 8.256 .