Local zoning · San Mateo County

San Mateo County — Historic Preservation

Historic Preservation under the San Mateo County local zoning and planning code, with the controlling citations.

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Last reviewed: July 3, 2026

Overview

San Mateo County’s historic-preservation rules for unincorporated areas are codified mainly in Chapter 8.428 of the County Zoning & Development Code (Title 8). The chapter establishes how County historic landmarks and historic districts are designated, what activities require a historic-preservation permit, and the review/appeal process (including referral to the Historic Resources Advisory Board). See the County’s purpose and definitions at § 8.428.010–§ 8.428.020 for the controlling policy language .

This page explains the County-specific standards and procedures that apply only in unincorporated San Mateo County (the ordinance does not govern incorporated cities). It links to related development topics you’ll likely need during a project: development standards, design review, overlays, parking, variances, nonconforming uses, landscaping, and the state building code.

What the ordinance actually requires (high‑level)

  • County purpose and definitions: § 8.428.010 (purpose) and § 8.428.020 (definitions) define the program intent and terms such as Alteration, Construction, Demolition, Historic District, Historic Resource, Landmark, and Landmark Site .
  • Criteria to designate landmarks/districts: the Board of Supervisors may designate when criteria in § 8.428.030 are met (e.g., architectural, historical, associative significance) .
  • Designation procedure and recording: applications, referral to the Historic Resources Advisory Board (HRAB), public hearings before the Planning Commission and Board of Supervisors, and recording the designation within 30 days are set out in § 8.428.040 .
  • Historic‑preservation permits: a permit is required to demolish, alter, or relocate any structure designated as a County Historic Landmark or in a County Historic District, and for changes to signs, exterior lighting, fences, parking areas, or other features within landmarks/districts (§ 8.428.050) .
  • Permit review rules and standards: application contents, HRAB referral, public hearing, and the review standards (alteration, construction, demolition standards) are in § 8.428.060; alterations must conform to the County’s Historic Resources Element guidelines and must not damage exterior historic character; demolition requires a careful set of findings including economic hardship and uniqueness criteria (§ 8.428.060(4)) .
  • Uses in historic structures: the County authorizes the Planning Commission to allow uses otherwise prohibited by base zoning, when the Commission finds the use contributes to preservation and is compatible; the special rules for uses in historic structures/districts appear at § 8.280.010(g) and include additional Coastal Zone findings where applicable .
  • Exceptions and flood/other overlays: the County may grant exceptions for reconstruction/rehabilitation of historic structures under the floodplain/flood-hazard rules in § 8.300.090, and other chapters reference special exceptions for historic resources .

District-by-district breakdown (how historic rules interact with specific County districts)

Note: Historic-preservation Chapter 8.428 establishes a designation and permit overlay that applies to parcels wherever the Board designates them — the base zoning district (RM, R-1, C-1, etc.) remains operative for other development rules. The ordinance discusses several actual County district chapters that commonly intersect with historic preservation; where the historic chapter does not set numeric dimensional standards for a base district, the base district chapter controls and is cited below. Where the County code does not provide historic‑specific numeric standards for a district, the item below states that fact and instructs to verify parcel-specific rules with the County.

Historic Landmark / Historic District (designation overlay)

  • Purpose: preserve resources of historic, cultural, architectural, archaeological, or aesthetic significance and to integrate preservation into land‑use review § 8.428.010 .
  • Typical permitted uses: designation itself does not change base zoning uses except that the Planning Commission may allow uses not normally allowed by the zoning if they are compatible and preserve the resource (§ 8.280.010(g)) .
  • Key development controls specific to the designation:
    • Permits required for demolition, alteration, relocation of designated landmarks/district resources and for alterations to signs/lighting/fences/parking within the district (§ 8.428.050) .
    • Application and documentation (elevations, photos, site plan) are required for preservation permits (§ 8.428.060(1)) .
    • Alterations must conform to the Guidelines for Historic Rehabilitation in the County General Plan’s Historic Resources Element (§ 8.428.060(4)(a)) .
  • Where it applies: to parcels or areas expressly designated by Board resolution and recorded with the County Recorder (§ 8.428.040(7)) .

Resource Management District — RM (and RM-CZ)

  • Purpose: conserve open‑space, natural resources, and ensure General Plan consistency § 8.134.010 and § 8.138.010 .
  • Typical permitted uses: low‑density residential, resource management uses; specific allowed forms are in each district chapter (see district chapters) .
  • Historic interaction:
    • Development in RM/RM‑CZ typically requires Development Review and must meet RM design criteria — historic resources in RM/RM‑CZ are still subject to Chapter 8.428 procedures for designation and for any demolition/alteration permits (see § 8.428.050–060) .
    • Tree/landscape rules and protection of cultural resources apply; see the County’s design criteria and landscaping and screening rules referenced in RM chapters (examples: § 8.318.100 and RM chapters) .
  • Key numeric dimensional standards (height, setbacks, lot coverage): RM chapters list these district-specific standards; the historic chapter does not prescribe different numeric standards. For parcel‑specific dimensional standards, verify the applicable RM section and any recorded development plan (Not found in retrieved materials in Chapter 8.428) .

Planned Agricultural District — PAD

  • Purpose: preserve agricultural land (see PAD chapter).
  • Historic interaction: historic resource exceptions and review pathways are available; PAD developments are subject to the same historic-permit triggers in § 8.428.050 and the County may apply the historic‑resource exceptions described in flood/exception chapters (§ 8.300.090) where relevant .
  • Numeric standards: PAD chapter supplies lot/ setback standards; 8.428 does not substitute numeric standards for PAD (Not found in retrieved materials).

R‑1, C‑1, C‑2 and other base zoning districts

  • Purpose and dimensional standards: each base district chapter (e.g., R‑1 family residential, C‑1 neighborhood commercial) contains the numeric development standards (height, setbacks, lot coverage, FAR). The historic-preservation chapter does not restate these numeric figures — instead it overlays permit requirements and a path for compatibility findings (§ 8.428.050–060 and § 8.280.010(g)) .
  • Typical use outcome: if a structure in any district is designated, ordinary zoning remains, but any demolition/alteration of the historic resource requires the historic-preservation permit and the Planning Commission must make compatibility/preservation findings before authorizing a nonconforming use in a landmark (§ 8.280.010(g)) .
  • Numeric standards for each zone: Not found in Chapter 8.428 (verify with the applicable district chapter and the County Zoning map) — Verify with the jurisdiction.

Timber Production Zone — TPZ / TPZ‑CZ

  • Purpose: manage timberland uses; like other districts, TPZ developments fall under historic-preservation permit triggers if a designated landmark/resource is present (§ 8.428.050) and are subject to review under TPZ development rules as well .

Practical takeaway: Chapter 8.428 works as an overlay: it creates designation, permit triggers, review steps, and substitutional findings for uses in designated resources. Base‑zone numeric standards remain in the base zone chapters and are not replaced by Chapter 8.428 unless a separate exception is granted under the County’s exceptions/variances rules § 8.300.090 or other code provisions .

Quick reference table — decision‑relevant items

Decision point / permitted activity What the code says (short) Code Reference
Require historic preservation permit for demolition/alteration/relocation A permit is required to demolish, alter, or relocate any structure designated as a landmark or inside an historic district; signs, fences, lighting, parking changes also require permits in districts/landmarks § 8.428.050
How to get a landmark/district designated Any person/group may apply; application must include APN(s), map, description of historic value, photos, condition statement; HRAB referral and public hearings required; Board records resolution and County Recorder records it § 8.428.040
Review criteria for alterations Alterations must conform to the County Historic Rehabilitation Guidelines in the General Plan’s Historic Resources Element and must not detrimentally alter exterior architectural character § 8.428.060(4)(a)
Review criteria for new construction in district New construction in an historic district must be compatible with the external appearance of existing designated landmarks § 8.428.060(4)(b)
When the Planning Commission can allow otherwise‑prohibited uses Planning Commission may permit uses not allowed by zone if they preserve the resource and meet findings (compatibility, impacts mitigated), incl. Coastal Zone additional findings § 8.280.010(g)
Exceptions for floodplain/substantially improving historic structures Director/County may grant exceptions to certain development standards to allow rehab/restoration of historic structures per § 8.300.090 § 8.300.090
Appeal path Planning Commission actions are appealable to the Board of Supervisors; permits may be appealed within 10 calendar days § 8.428.060(5) and related appeals language

Checklist — what an applicant must submit / satisfy (project-level)

  • Complete County application form for historic designation or historic‑preservation permit (file with the Planning and Development Division) § 8.428.040(1) / § 8.428.060(1)
  • Include Assessor’s Parcel Number(s), map/boundary for district requests, description of historic/cultural value, photographs, and a statement of condition § 8.428.040(2)
  • Provide elevation drawings, site plan, and photos for any proposed alteration/construction; Coastal projects must include proposed use per § 8.428.060(1)
  • Prepare to be referred to the Historic Resources Advisory Board (HRAB) for comment; incorporate HRAB recommendations in Planning Commission report § 8.428.060(2)
  • Attend public hearings before the Planning Commission and Board of Supervisors (notice and hearing requirements apply) § 8.428.040(4–5)
  • If demolition is proposed, be prepared for the Commission to evaluate economic hardship and uniqueness criteria and to delay demolition by up to 180 days (plus possible extension) § 8.428.060(3)
  • If a use is proposed that is not normally allowed by the base zoning, secure the Planning Commission findings under § 8.280.010(g) and HRAB review
  • Confirm compliance with any applicable overlay rules (Coastal, flood, RM design criteria) and supporting technical studies; use development standards and design review resources as needed.

Risks & Ambiguities

Issue Why it matters What to verify
Applicability inside the Coastal Zone Coastal projects may require a Coastal Development Permit in addition to historic permit; Coastal-specific findings apply Verify coastal status and Coastal Zone permit needs per § 8.428.050 and § 8.280.010(g)
Base‑zone numeric standards not stated in Chapter 8.428 Chapter 8.428 triggers permit and review but does not list setbacks/height/lot coverage numbers Check the specific base district chapter (e.g., R‑1, RM, PAD) for numeric standards; Chapter 8.428 does not supply these (Not found in retrieved materials). Verify with the jurisdiction.
“Compatible use” determinations are discretionary Planning Commission has subjective findings to make for uses that depart from base zoning — outcomes can vary Prepare materials demonstrating how the proposed use will preserve the landmark and mitigate impacts; HRAB referral is required § 8.280.010(g)
Demolition delay / economic hardship evaluation Commission can deny or delay demolition and evaluate economic use of the property Expect a possible 180‑day review stay for demolition applications; compile economic/structural analyses § 8.428.060(3)
Interplay with floodplain, hazard, and exceptions chapters Flood or hazard regulations may add or change permit/exception pathways See § 8.300.090 for exceptions for historic structures and verify flood maps and required justifications

Plain‑English summary

If your property in unincorporated San Mateo County is designated a County Historic Landmark or lies inside a County Historic District, you must get a County historic‑preservation permit before demolishing, moving, or making exterior changes (including signs, fences, lighting and parking). The application goes to the Historic Resources Advisory Board for review and then to the Planning Commission (and possibly the Board of Supervisors) for final action; the County evaluates compatibility with historic‑resource guidelines and can allow uses that aren’t normally permitted only when they demonstrably help preserve the resource (§ 8.428.050–§ 8.428.060 and § 8.280.010(g)) .

Source References

  • San Mateo County Zoning & Development Code — Article 8, Chapter 8.428 (Historic Preservation: Purpose, Definitions, Criteria, Designation procedures, Permits, Permit procedures): § 8.428.010–§ 8.428.060 .
  • Uses in historic structures and Planning Commission findings: § 8.280.010(g) .
  • Exceptions for reconstruction/rehabilitation (flood/other): § 8.300.090 .
  • RM / RM‑CZ district purpose and requirements (development review interaction): § 8.134.010 and § 8.138.010–§ 8.138.040 .
  • Design criteria and cultural resource design criteria referenced by development review: § 8.318.100 (Design Criteria) .

If you need the exact ordinance text or help preparing the HRAB/Planning Commission packet (photos, elevations, economic analysis for a demolition request), I can outline a document checklist mapped to the exact subsections above. Verify any parcel‑specific requirements (zoning map designation, overlays, flood maps) with County planning staff before filing.

Sources

Retrieved passages

  • San Mateo County Zoning Code (Title 8) High relevance
  • San Mateo County Zoning Code (Title 8) High relevance
  • San Mateo County Zoning Code (Chapter 4) High relevance
  • San Mateo County Zoning Code (section 8.280.010) High relevance
  • San Mateo County Zoning Code (section 8.428.030.) High relevance
  • San Mateo County Zoning Code (section 8.428.040) High relevance
  • San Mateo County Zoning Code (Title 8) High relevance
  • San Mateo County Zoning Code (Chapter 8.428) High relevance
  • San Mateo County Zoning Code (Chapter 8.348) Medium relevance
  • San Mateo County Zoning Code (chapter are) Medium relevance
  • San Mateo County Zoning Code (Section 12) Medium relevance
  • San Mateo County Zoning Code (Chapter 20A.2) Medium relevance
  • San Mateo County Zoning Code (Title 8) Medium relevance
  • San Mateo County Zoning Code (Section 8.132.090.) Medium relevance

Cited sections

Frequently asked questions

How does San Mateo County define an "historic landmark" or "historic district"?

A County Landmark or Historic District is defined in § 8.428.020: a landmark is a historic resource with special historical, cultural, archaeological, aesthetic, or architectural value; a historic district is an area containing improvements that constitute a distinct section of the County and have special historical or aesthetic value. The definitions and scope are in § 8.428.020 .

What activities trigger a historic‑preservation permit in unincorporated San Mateo County?

A historic‑preservation permit is required to demolish, alter, or relocate any structure designated as a County Historic Landmark or located in a County Historic District, and for constructing/placing/altering signs, exterior lighting, fences, parking areas, or other exterior features within a landmark or district (§ 8.428.050) .

Who reviews and recommends on historic‑preservation applications?

The Planning Division refers historic‑preservation permit and designation applications to the Historic Resources Advisory Board (HRAB) for review and recommendation; HRAB reports to the Planning Commission, which holds the public hearing and makes decisions subject to appeal to the Board of Supervisors (§ 8.428.060(2) & § 8.428.040(3–6)) .

Can the County allow a use that’s not allowed by the base zoning because the building is historic?

Yes. Under § 8.280.010(g) the Planning Commission may permit uses otherwise prohibited by the zoning if the use is determined compatible with a structure listed in the National Register, a County Historic Landmark, or a County Historic District, subject to HRAB review and the Commission’s findings (the use must contribute to preservation and not harm surrounding uses) .

Will the County allow demolition of a designated landmark?

Demolition is not prohibited outright, but demolition permits for landmarks are tightly controlled: the Planning Commission evaluates factors (e.g., national/state significance, rarity of materials/design, reasonable economic use) and may delay or deny demolition; demolition review can include a stay of up to 180 days and possible extension by the Board of Supervisors § 8.428.060(3–4) .

Do I need special exceptions if the historic building is in a floodplain or hazard area?

Possibly. § 8.300.090 allows the Director or County to grant exceptions for reconstruction/rehabilitation/restoration of historic structures (including those on inventories or County landmarks) from certain floodplain restrictions when strict compliance would prevent preservation; specific findings and technical justification are required .

What materials do I need to submit for an alteration or new‑construction project in a historic district?

The County requires elevation drawings, photographs of existing and adjacent structures, a site plan, and (for Coastal Zone projects) a proposed use statement. These application requirements are listed in § 8.428.060(1) .

Does the historic preservation chapter set setbacks, height, or lot‑coverage numbers for historic properties?

No. Chapter 8.428 creates designation and permit triggers and establishes review standards for compatibility and preservation; it does not replace the base zone numeric standards (setbacks, height, lot coverage) — those remain in the applicable zoning district chapter (e.g., RM, R‑1). If an exception is necessary, see County variances and exceptions and § 8.300.090 for possible historic exceptions (verify with the jurisdiction) .

How long is a historic‑preservation permit valid?

A permit expires if substantial work is not commenced within one year of issuance or is not completed within one year of commencement unless the permit specifies otherwise; see the permit-duration rules referenced in Chapter 8.428 (permit duration language) .

If my application is denied, how do I appeal?

Actions by the Planning Commission regarding historic permits may be appealed to the Board of Supervisors by filing a written notice of appeal within ten calendar days of the decision; see § 8.428.060(5) and related appeals language for procedures and timing .

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