Local zoning · San Bruno

San Bruno — Nonconforming Uses

Q: My building was damaged in an earthquake — can I rebuild a nonconforming structure?

If the nonconforming building is damaged to more than 50% of its value, restoration may proceed only if you obtain a use permit and provide a certified appraisal approved by the Community Development Director; if damage is 50% or less , you can rebuild up to the former floor area and re‑establish the nonconforming use. § 12.92.020(B)(5); § 12.92.020(C)(3–4) .

Q: Are older second units (excess housekeeping units) treated as nonconforming in San Bruno?

Yes — a single excess housekeeping unit built prior to June 30, 1977 can be a legal nonconforming unit if it complied with the rules in effect when built and isn’t a nuisance; such units may not be enlarged (structural alterations that increase floor area are prohibited) and only one is allowed per lot. The owner must prove the unit’s status; the Director can issue a written determination (appealable). § 12.92.030 .

Q: If my property is in a mixed‑use district (e.g., TOD‑2), how do nonconforming uses interact with permitted uses?

Mixed‑use districts (CBD, TOD‑S , TOD‑1 , TOD‑2 , MX‑R ) have a use matrix (Table 12.280‑1 ) that lists permitted (P) and conditional (C) uses; if a legally existing use becomes nonconforming because of zoning change, it is governed by Chapter 12.92 for continuance and limitations. § 12.280.020 ; § 12.92.020 .

Q: Can a nonconforming setback be fixed by enlarging other parts of the building?

Physical changes that increase the extent of a setback or other dimensional nonconformity are not permitted without first securing a conditional use permit ; the Director decides during plan check whether a proposed alteration increases nonconformity — that decision can be appealed. § 12.92.020(C)(1–2) .

Nonconforming Uses under the San Bruno local zoning and planning code, with the controlling citations.

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Last reviewed: July 2, 2026

Overview

San Bruno’s rules for nonconforming lots, structures and uses are codified in Chapter 12.92 of the municipal zoning ordinance and the related definitions and district rules throughout Title 12. They establish (1) what counts as a lawful nonconforming use/structure/lot, (2) limits on expanding or changing nonconformities, (3) time limits for re‑establishment after cessation, and (4) how repair/restoration after damage is treated. See the ordinance intent and continuance rules at § 12.92.010 and § 12.92.020 for the controlling provisions.

Note: this page sticks only to the City zoning provisions on nonconformities; it does not attempt to cover building-code (Title 24), rental/tenant law, or other state housing statutes except where the local code explicitly references or is constrained by them. For state ADU nonconforming rules referenced by the city, see the California ADU guidance in the materials.

(Links to related San Bruno topics used below: see parking, development standards, design review, overlay districts, ADUs, and the California Building Standards Code.) San Bruno Parking San Bruno Development Standards San Bruno Design Review San Bruno Overlay Districts San Bruno ADUs California Building Standards Code

Key city rules (what the code actually says)

Lawful nonconforming uses (use conflicts with current permitted uses) are allowed to continue but: may not be expanded, may not be changed to a different nonconforming use, and if discontinued for six continuous months the nonconforming status lapses (with limited extensions available through the Community Development Director). § 12.92.020(A)(1–3).
Nonconforming uses occupying a conforming structure can continue but cannot expand to occupy a larger area; changing to a more-conforming use is allowed only with a use (conditional) permit; cessation for six months terminates the status. § 12.92.020(B)(1–4).
Nonconforming structures (setback or dimensional nonconformities, or residential uses in a commercial/industrial district) are lawful but physical changes that increase the extent of nonconformity require a conditional use permit; repairs that do not increase the nonconformity may proceed with normal building permits and plan check. § 12.92.020(C)(1–2).
Damage/Destruction rules: a nonconforming use or structure damaged more than 50% of value may only be restored subject to obtaining a use permit and an appraiser’s valuation approved by the Community Development Director; if damage is ≤ 50% the structure may be rebuilt to its former floor area and the nonconforming use reestablished. § 12.92.020(B)(5), (C)(3–4).
Special rule for pandemic-era cessations: if a nonconforming use was discontinued between January 1, 2020 and May 1, 2021, the six‑month abandonment clock is tolled until May 1, 2021. Extensions can be requested in writing to the Community Development Director. § 12.92.020(A)(3)(a).
Excess housekeeping units (older second units) are treated as a specific nonconforming category: a single excess housekeeping unit built before June 30, 1977 that otherwise met the then-law can be a legal nonconforming use but is strictly limited (one per lot; no floor‑area increases that enlarge the unit; maintenance allowed; burden of proof on owner). § 12.92.030.
Substandard lots: the code permits use of a substandard lot as a building site under the conditions listed in § 12.92.040 (standards for when a substandard lot may be used alone as a building site are spelled out there). § 12.92.040.

District-by-district summary (what the city zoning ordinance shows)

Below are the San Bruno zoning districts called out in Title 12. For each district I list what the ordinance text in the retrieved materials actually provides about the district purpose, typical permitted uses, key dimensional standards (if available in the retrieved material), and where the district applies. If the ordinance text with numeric dimensional standards or use lists was not included in the retrieved materials for a district, I note that explicitly so you can Verify with the jurisdiction.

Note: the City’s list of district codes and many mixed‑use district rules are in Article/Chapters referenced below; see the code citations at the end of this page for the full locations. Always verify specific property zoning on the City zoning map as the code directs. § 12.96.010.

R-1 (Single-family residential)

Purpose: R-1 is the single‑family residential district as listed in the district table. § 12.96.060.
Typical permitted uses: Not found in retrieved materials for the R‑1 list beyond the district name; verify with the City code pages for permitted uses in residential districts. Not found in retrieved materials.
Key dimensional standards: Not found in retrieved materials (setbacks, lot sizes, coverage not shown in retrieved snippets). Verify with San Bruno Development Standards and the relevant zoning district table. San Bruno Development Standards
Where it applies: Citywide residential neighborhoods per the zoning map; see § 12.96 listings. § 12.96.010.

R-2 (Low density residential)

Purpose & permitted uses: R-2 listed as “Low density residential” in the district index. Specific uses / standards not present in retrieved snippets. § 12.96.070.
Key dimensional standards: Not found in retrieved materials — verify with development standards.

R-3 (Medium density residential)

Purpose & permitted uses: District listed; detailed use table not in retrieved snippets. § 12.96.080.
Key dimensional standards: Not found in retrieved materials. Verify with the development standards.

R-4 (High density residential)

Purpose: R-4 is the “High density residential district.” § 12.96.090.
Uses/standards: Not found in the retrieved snippets; verify with the zoning use tables and development standards.

C-N (Neighborhood commercial)

Purpose: C-N listed as Neighborhood commercial. § 12.96.100.
Typical uses & dimensional standards: Not included in the retrieved fragments. For mixed-use corridor districts (CBD, TOD, MX-R) the code provides detailed use matrices — see below. Otherwise verify with district use tables in Title 12.

A-R (Administrative & Research)

Purpose: A-R listed as Administrative and Research district. § 12.96.130.
Uses/standards: Not found in the retrieved snippets. Verify with Title 12 use tables.

M-1 (Industrial)

Purpose: M-1 Industrial. § 12.96.150.
Uses/standards: Not shown in the retrieved fragments. Verify with Title 12.

O (Open space and conservation)

Purpose: O Open space/conservation. § 12.96.170.
Standards: Not found in retrieved snippets.

U (Unclassified)

Purpose/status: U is Unclassified; see district index. § 12.96.180.

Planned / Special & Overlay districts (where the code gives more detail)

P‑D (Planned Development) — listed in the district index; specific PD standards are project‑specific (see each PD zoning text). § 12.96.200.
ES (Emergency Shelter overlay) — listed; see overlay rules (not reproduced in the retrieved snippets). § 12.96.205 referenced.
CBD / TOD‑S / TOD‑1 / TOD‑2 / MX‑R — Mixed‑use and transit‑oriented districts. The code includes a detailed uses matrix (Table 12.280‑1) and development standards (Table 12.280‑2) for these districts; § 12.280.020 describes permitted vs conditional uses and how unlisted uses are treated. See Table 12.280‑1 (uses) and § 12.280.030(A) on design review/architectural review permits. § 12.280.020–12.280.030.
- Example: TOD‑2 (High Density Mixed‑Use) — described as allowing high‑intensity residential and commercial uses along transit corridors to encourage pedestrian activity and transit use; it implements General Plan Transit‑Oriented designations. § 12.280.020(E).
- Example: MX‑R (Multi Use – Residential Focus) — allows multifamily housing and residentially focused uses along El Camino Real; retail generally conditional. § 12.280.020(E).
- Table entries for permitted uses (e.g., CBD, TOD‑1, TOD‑2, MX‑R) are shown in Table 12.280‑1; see that table for use‑by‑district status (P/C/–). § 12.280.020 and Table 12.280‑1.
Bayhill specific districts (BRO, BNC, BR, BMU) — the Bayhill Specific Plan zoning districts have explicit numeric development standards in Table 12.290‑3 (minimum lot size, maximum lot coverage percentages for different uses, building length caps, and setback measurement rules). Example items from the table: minimum lot sizes for Bayhill Regional Office (35,000 sf) and Bayhill Neighborhood Commercial (25,000 sf); maximum lot coverage values differ by use (commercial/office/residential percentages called out). See § 12.290.060 and Table 12.290‑3 for the Bayhill district standards.

Quick decision table (most decision‑relevant rules / permitted uses)

Topic	What the code allows / forbids	Code Reference
Continue an existing nonconforming land use	Allowed to continue but may NOT be expanded or changed to a different nonconforming use; 6‑month abandonment rule.	§ 12.92.020(A)(1–3)
Nonconforming use in a conforming structure	May continue; may not occupy a larger area; change to more‑conforming use requires use permit; 6‑month abandonment rule.	§ 12.92.020(B)(1–5)
Nonconforming structure (setback/dimensions)	Structural changes that increase nonconformity require a conditional use permit; minor alterations not increasing nonconformity may proceed via regular building permits.	§ 12.92.020(C)(1–2)
Damage >50% of value	Restoration allowed only with a use permit and certified appraisal approved by Director; ≤50% may be rebuilt to former floor area.	§ 12.92.020(B)(5); § 12.92.020(C)(3–4)
Excess housekeeping (old second units)	One allowed if constructed before June 30, 1977 and met the law then; strict limits on alteration and documentation burden on owner.	§ 12.92.030
Mixed‑use district permitted uses	Table 12.280‑1 lists P/C/– designations for CBD, TOD‑S, TOD‑1, TOD‑2, MX‑R and their permitted uses.	§ 12.280.020 and Table 12.280‑1
Bayhill numeric development standards	Bayhill Table 12.290‑3: minimum lot sizes (e.g., 35,000 sf for BRO), maximum lot coverage by use, building length caps.	§ 12.290.060 and Table 12.290‑3

Checklist — what an applicant must demonstrate (zoning/entitlement focus)

Proof the use/structure/lot was lawfully established under the zoning rules in effect when it began (burden of proof for certain nonconformities and excess housekeeping units). § 12.92.010; § 12.92.030(A)(2–3).
If proposing any physical alteration to a structure that is nonconforming, show that the work will not increase the nonconformity (or apply for a conditional use permit if it will). § 12.92.020(C)(1–2).
If seeking to re‑establish a use after closure, confirm the continuous cessation was less than six months, or obtain a written extension from the Community Development Director. § 12.92.020(A)(3).
If restoration after damage is proposed and damage > 50%, provide a certified real‑estate appraisal and apply for a use permit. § 12.92.020(B)(5); (C)(3).
For an excess housekeeping unit claim, supply documentation proving the unit was built before June 30, 1977 and was lawful at the time; pay the application fee for a director determination if requested. § 12.92.030(A)(1–3).
For any conditional use or use‑permit requests related to changing/expanding nonconforming uses, follow the procedures in the use permit chapter and expect findings on compatibility, density/intensity, and public welfare. (See § 12.280.020 on unlisted uses and conditional process references.) § 12.280.020.

Risks & Ambiguities

Issue	Why it matters	What to verify
Claiming lawful nonconforming status	City requires the use/structure to have been lawful under prior rules; owner bears proof in certain cases (excess housekeeping units explicitly place burden on owner). If you cannot prove it, the nonconforming protections may not apply.	Verify historic permits/records; ask the Community Development Director for a written determination. § 12.92.030(A)(2–3).
Whether a proposed change “increases nonconformity”	The Director decides in the plan‐check whether an alteration increases nonconformity; that decision can be appealed. Uncertainty can cause delays or require a conditional use permit.	Obtain a pre‑application meeting and written determination from the Community Development Director; know appeal routes referenced in the section. § 12.92.020(C)(2).
Damage threshold (50%) valuation	The code ties permissive restoration to a 50% of value threshold determined by a certified real‑estate appraiser approved by the Director — appraisal methodology affects whether a use can be restored without a use permit.	Confirm appraisal scope and Director’s approval requirement before contracting an appraiser. § 12.92.020(B)(5); (C)(3).
Single‑family expansion exemption	The code contains an exemption stating that permitted single‑family residential uses made legal nonconforming by adoption of the ordinance shall be exempt from the prohibition on expansion in § 12.92.020(B)(2) — but the interplay with other rules (e.g., parking) can be ambiguous.	Verify whether your property qualifies for the single‑family exemption and whether parking or other chapters impose incremental requirements. § 12.280.020(C)(2); § 12.100.020.
Interplay with ADU rules and state law	State ADU statutes limit a city’s ability to deny an ADU because of nonconforming zoning conditions; San Bruno references state ADU law in practice. Local nonconforming rules still matter for other entitlements.	For ADU projects, check state ADU guidance and the city’s ADU chapter; do not assume local nonconforming conditions will block an ADU permit absent specific state exceptions. See California ADU guidance in the uploaded materials.
Parcel-specific dimensional standards	Many district numeric standards (setbacks, lot coverage, height) were not present in the retrieved snippets for the basic residential districts. Without those, it’s hard to judge whether a structure is nonconforming.	Verify exact zoning district for the parcel and consult the specific development standards tables or San Bruno Development Standards. § 12.96.010.

Plain‑English summary

If your property or business was legal when it started but no longer meets today’s zoning rules, San Bruno lets that use or structure continue in many cases — but you generally cannot expand it, switch it to another nonconforming use, or leave it unused for more than six months without losing the protection. Major repairs after big damage and any physical changes that increase a setback or other dimensional nonconformity usually require a special permit and additional documentation. § 12.92.010–.040.

Source References

Chapter 12.92, “Nonconforming Lots, Structures and Uses” — § 12.92.010 (Intent & Applicability).
Chapter 12.92 — § 12.92.020 (Continuance of nonconformities: Nonconforming uses of land; uses in conforming structures; nonconforming structures; damage/repair rules).
Chapter 12.92 — § 12.92.030 (Excess housekeeping units; pre‑1977 second units).
Chapter 12.92 — § 12.92.040 (Substandard lot/building site rules).
Definitions: § 12.80.350 (“Nonconforming use”) and § 12.80.345 (“Nonconforming sign”).
District index and list: § 12.96.010 (R‑1, R‑2, R‑3, R‑4, C‑N, A‑R, M‑1, O, U, P‑D, ES, CBD, TOD, MX‑R, Bayhill districts).
Mixed‑use districts: § 12.280.020 (permitted/conditional uses) and Table 12.280‑1 (permitted land uses for CBD, TOD, MX‑R).
Bayhill specific plan standards: § 12.290.060 and Table 12.290‑3 (minimum lot sizes, lot coverage, building mass/length).
Off‑street parking applicability to existing/nonconforming uses: § 12.100.020 and § 12.100.030 (parking rules and application to existing development).
California ADU guidance (uploaded reference used for how state ADU law interacts with local nonconformance): California ADU handbook excerpts in uploaded materials.

Sources

Retrieved passages

San Bruno Zoning Code (section may) High relevance
San Bruno Zoning Code (§ 3) High relevance
San Bruno Zoning Code (§ 27-6.2) High relevance
San Bruno Zoning Code (§ 27-3.1) High relevance
CPC § 3 (§ 3) High relevance
San Bruno Zoning Code (§ 27-6.2) High relevance
CBC § 66321 (§ 66321) Medium relevance
San Bruno Zoning Code (chapter may) Medium relevance

Cited sections

Official San Bruno code library

Frequently asked questions

What happens if my nonconforming business stops operating for six months in San Bruno?

If a lawful nonconforming use is discontinued for a continuous period of six months, the nonconforming status is lost and the subsequent use must conform to current zoning; you can apply to the Community Development Director for an extension if the cessation was for reasons outside the owner’s control. § 12.92.020(A)(3).

Can I expand a nonconforming use or make it larger inside the same building?

No — the ordinance forbids expanding a nonconforming land use, and a nonconforming use within a conforming structure may not occupy a greater area than it currently does; changes that increase nonconformity typically require a use (conditional) permit. § 12.92.020(A)(1); § 12.92.020(B)(2); § 12.92.020(C)(1).

My building was damaged in an earthquake — can I rebuild a nonconforming structure?

If the nonconforming building is damaged to more than 50% of its value, restoration may proceed only if you obtain a use permit and provide a certified appraisal approved by the Community Development Director; if damage is 50% or less, you can rebuild up to the former floor area and re‑establish the nonconforming use. § 12.92.020(B)(5); § 12.92.020(C)(3–4).

Are older second units (excess housekeeping units) treated as nonconforming in San Bruno?

Yes — a single excess housekeeping unit built prior to June 30, 1977 can be a legal nonconforming unit if it complied with the rules in effect when built and isn’t a nuisance; such units may not be enlarged (structural alterations that increase floor area are prohibited) and only one is allowed per lot. The owner must prove the unit’s status; the Director can issue a written determination (appealable). § 12.92.030.

If my property is in a mixed‑use district (e.g., TOD‑2), how do nonconforming uses interact with permitted uses?

Mixed‑use districts (CBD, TOD‑S, TOD‑1, TOD‑2, MX‑R) have a use matrix (Table 12.280‑1) that lists permitted (P) and conditional (C) uses; if a legally existing use becomes nonconforming because of zoning change, it is governed by Chapter 12.92 for continuance and limitations. § 12.280.020; § 12.92.020.

Can a nonconforming setback be fixed by enlarging other parts of the building?

Physical changes that increase the extent of a setback or other dimensional nonconformity are not permitted without first securing a conditional use permit; the Director decides during plan check whether a proposed alteration increases nonconformity — that decision can be appealed. § 12.92.020(C)(1–2).

Will San Bruno deny an ADU application because of existing nonconforming zoning conditions?

State ADU law limits a local agency’s ability to deny an ADU permit just because of existing nonconforming zoning conditions; the city’s materials reference that state guidance. You still must meet other applicable standards; check the city ADU chapter and state ADU rules for specifics. See the California ADU guidance included in the city materials.

How do I prove my unit or use is legally nonconforming?

For certain categories (such as excess housekeeping units) the code explicitly places the burden of proof on the owner and provides a Director determination process (with an application fee and appeal rights). For other nonconformities you should assemble historical permits, building plans, tax records, and other contemporaneous documentation and seek a written determination from the Community Development Director. § 12.92.030(A)(2–3); § 12.92.010(B).

What does San Bruno require if an existing nonconforming building wants to change to a “more conforming” use?

A nonconforming use of a conforming structure may be changed to a use of a similar or more conforming nature provided a conditional use permit is first obtained. Be prepared to meet the findings and conditions associated with a use permit. § 12.92.020(B)(3). ---

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