Local zoning · San Marcos

San Marcos — Nonconforming Uses

Q: How long can I stop operating a nonconforming use before I lose the right to resume it?

If a nonconforming use is discontinued for 12 consecutive months , the right to continue that nonconforming use is deemed abandoned; the Director can grant a single extension for up to 12 months in specific hardship or investment circumstances (total discontinuance limit 24 months ) ( § 20.345.030.J–M ) .

Q: Are industrial uses in Transitional Zones governed by the nonconforming chapter?

The Ordinance says Chapter 20.345 rules do not apply to industrial uses within a Transitional Zone where ongoing industrial activities consistent with the Initial Zone are not treated as nonconforming — verify whether your parcel is in a Transitional Zone ( § 20.235.060.B–C ) .

Q: Who can approve an extension of nonconforming status and what is the timeline?

The Director handles extension requests and must act on a complete application within set timelines; preliminary decisions, neighbor notice, and the 50‑day decision window (with specific hearing and appeal rights) are described in the application process for extension ( § 20.345.030.M; 20.500.030 ) .

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

Ask a question free See coverage

Last reviewed: July 2, 2026

Overview

San Marcos regulates nonconforming uses, structures, and lots through Chapter 20.345 — Nonconforming Uses and Structures of the Zoning Ordinance. The chapter defines when an existing lawful use or building becomes nonconforming, what maintenance and repairs are allowed, the narrow ways a nonconformity can be altered or extended, and the deadlines and findings for re‑establishing or discontinuing nonconforming activity (§ 20.345.010–070) . For basic context about how zones and development standards interact with nonconforming rules, see the city’s San Marcos zoning overview and the Zoning Ordinance (linked below).

Important cross-topics (see links used below): the city’s rules interact with local rules for parking, design review, ADUs, overlays, and state building rules such as the California Building Standards Code — each of which appears in separate chapters and may affect whether a nonconforming feature can be repaired, rebuilt, or expanded. For example, ADU review in San Marcos refers to statewide ADU rules and local implementation that limit when a nonconforming zoning condition may block an ADU permit; see San Marcos ADU rules and the statewide guidance in the ADU handbook included in the record.

(First mentions linked to the GoCodebook menu pages: San Marcos zoning & planning overview, San Marcos Zoning, San Marcos Parking, San Marcos Design Review, San Marcos Overlay Districts, California Building Standards Code, San Marcos ADUs, San Marcos Variances and Exceptions.)

How San Marcos treats nonconformities (core rules)

A nonconforming use or structure must have been legally established under the law at the time it was created; the property owner carries the burden of proof that the nonconformity is lawful (§ 20.345.030.A) .
Residential nonconforming uses and structures may continue in place but generally cannot be enlarged or structurally altered in ways that increase the nonconformity except as expressly allowed in the chapter (§ 20.345.030.C–D) .
Nonresidential nonconforming uses and structures may continue but enlargement or intensification is tightly limited and requires manager/Director review or discretionary permits and findings (§ 20.345.030.E–F; § 20.345.050) .
Routine maintenance and ordinary repairs that do not increase nonconformity are allowed; examples include painting, roof replacement, and repairs required by law (§ 20.345.040) .
Abandonment/discontinuance for a continuous period of twelve (12) months generally extinguishes the nonconforming right; the Director can grant one extension for up to an additional twelve (12) months in specific circumstances (total discontinuance limit 24 months) (§ 20.345.030.J–L; M) .
If a nonconforming structure is moved or removed, the nonconforming status is lost and future use must conform to current rules (§ 20.345.030.P) .
If a nonconforming structure is damaged or destroyed, it may be rebuilt to its prior envelope and intensity if rebuilding meets timelines (building permits within one year and construction diligently completed within 18 months of permit) and nonconformities are not increased (§ 20.345.060) .
The Director may allow limited expansions of nonconforming structures subject to numeric caps and findings: residential expansions are capped at 10% gross habitable area under the chapter’s residential rules; nonresidential structures may receive up to 10% administratively and up to 20% via Director’s Permit/DP subject to findings and other development standards (§ 20.345.050) .
Illegal uses or structures that were unlawful when established are not protected by nonconforming provisions and are subject to abatement/enforcement (§ 20.345.020; 20.345.070) .

District-by-district guidance (San Marcos-specific)

Below are the districts that appear in the Zoning Ordinance where nonconforming rules are commonly encountered. Each subsection shows what the district is for, typical uses that become nonconforming, which parts of Chapter 20.345 apply, and where the district applies according to the ordinance text we retrieved.

Note: the Zoning Map assigns districts to parcels; verify parcel-specific zoning and numeric development standards with the City. If a numeric standard is not located in the retrieved materials below, the ordinance text for that numeric standard is Not found in retrieved materials and you must Verify with the jurisdiction.

Residential (R) — general

Purpose: provide locations for single- and multi-family housing and related neighborhood services and to implement residential General Plan designations (See § 20.100.040–G) .
Typical permitted uses: single-family homes, duplexes/attached units where allowed, accessory dwelling units (see local ADU chapter) and limited neighborhood services (depends on specific R designation).
Nonconforming specifics: residential nonconforming structures and uses may continue but additions or structural alterations that increase nonconformity are prohibited except as expressly allowed (small expansions allowed under § 20.345.050.A: 10% maximum gross habitable area expansion; expansion cannot increase stories and cannot reduce required parking) (§ 20.345.030.C–D; § 20.345.050.A) .
Where it applies: any parcel zoned in an R Zone on the Zoning Map; general applicability of Chapter 20.345 covers all Zones (§ 20.345.020; § 20.100.040.E) .
Verify with the jurisdiction: exact setback, lot coverage, FAR, and height caps for R-1, R-2, R-3 etc. (Not found in retrieved materials).

R-1-10

Purpose/usage: referenced as the fallback standard for residential nonconforming expansions when the previous zone was nonresidential. The ordinance uses R-1-10 setback and height rules as a baseline in that situation (§ 20.345.050.A.1) .
Typical permitted uses: single-family dwelling uses (local R-1-10 standards apply in full text elsewhere).
Key dimensional standards: the ordinance references applying R-1-10 setback and height standards when permitted under the nonconforming expansion rules, but the numeric setbacks/height for R-1-10 are Not found in retrieved materials here — Verify with the jurisdiction for the local R-1-10 development standards (see San Marcos Development Standards) .

Mixed Use — MU-3 (SP) and MU-4 (SP)

Purpose: higher-intensity mixed-use areas intended for mixed residential/commercial development, often within a Specific Plan; the code treats MU-3 and MU-4 planned uses differently and in places prevents the “similar use” rule from applying (unlisted uses) to MU-3/MU-4 pending Specific Plan processes (Table/Notes; see Table 20.230 and related notes) .
Typical permitted uses: mixed residential and commercial uses as defined in the specific plan (actual permitted uses are identified in the Specific Plan for the MU-3 (SP)/MU-4 (SP) areas).
Nonconforming specifics: Chapter 20.345 applies citywide, but permitted uses in MU-3 and MU-4 are handled during specific plan implementation and may not be subject to the “similar use” flexibility described in the main use tables; verify whether a given nonconformity is in a Specific Plan area (§ 20.400.020.D; Table notes) .
Where it applies: within Specific Plan boundaries; check the Zoning Map/Specific Plan documents (Not found in retrieved materials: full MU numerical standards).

Industrial (I) / Industrial Zones

Purpose: provide for industrial and related uses, subject to industrial development standards (CHAPTER 20.230; Section 20.235) .
Typical permitted uses: manufacturing, warehousing, vehicle storage and related industrial operations (see Table 20.230‑2 and Section 20.400 use standards) .
Nonconforming specifics: the Zoning Ordinance states the Chapter 20.345 nonconforming regulations shall not apply to industrial uses within any Transitional Zone where the “Initial Zone” rules continue to govern; i.e., industrial activities consistent with the Initial Zone are not treated as nonconforming in Transitional Zones (§ 20.235.060.B–C) . Otherwise, industrial nonconformities follow the standard Chapter 20.345 rules.
Verify with the jurisdiction: the exact industrial zone labels and dimensional/operational thresholds and whether a parcel sits in a Transitional Zone (Not found in retrieved materials: full numerical standards).

Commercial (C, NC)

Purpose: locations for retail, services, offices; the code references Commercial (C, NC) zones in specific use standards (e.g., massage establishments) (§ 20.400.250) .
Typical permitted uses: retail stores, restaurants, offices, personal services as specified in the Table of Uses (see Table 20.230-1/20.230-2).
Nonconforming specifics: nonconforming commercial uses may continue but cannot be structurally altered to increase nonconformity; expansions follow the same Chapter 20.345 thresholds and review paths (§ 20.345.030; § 20.345.050) .
Where it applies: parcels zoned Commercial per the Zoning Map (verify per parcel).

Public Institutional (P-I) and Open Space (OS)

Purpose: identified in Chapter 20.240. P‑I supports public buildings/institutions; OS protects open space and parks (§ 20.240.020.A–B) .
Typical permitted uses: civic buildings, schools, parks, limited maintenance uses.
Nonconforming specifics: land uses and structures in these Zones are still subject to the city’s overall nonconforming rules unless the chapter or other chapters specifically exempt certain public activities (§ 20.240.030; § 20.345.020) .
Where it applies: parcels mapped as P‑I or OS.

(If you need district numeric standards (setbacks, height, lot coverage, FAR) for any specific district, request the specific zone table or the Zoning Map/Development Standards chapter — those numeric values are Not found in retrieved materials above. See San Marcos Development Standards.)

Quick reference table — most decision-relevant nonconforming rules

Rule / Decision point	Rule summary	Code reference
Legal proof burden	Owner must show the use/structure was lawfully established to claim nonconforming status	§ 20.345.030.A
Routine maintenance allowed	Repairs/painting/roofing and aesthetic improvements allowed so long as they don't increase nonconformity	§ 20.345.040
Residential expansion cap	Residential expansion limited to 10% gross habitable area and cannot add stories; parking/access preserved	§ 20.345.050.A
Non-residential expansion caps	Admin: up to 10% floor area; DP: up to 20% with required findings	§ 20.345.050.B
Abandonment/discontinuance	Continuous discontinuance of 12 months = abandonment; Director may extend for up to 12 months (total 24)	§ 20.345.030.J–M
Rebuild after destruction	Building permit within 1 year and construction complete within 18 months; no increase in nonconformity	§ 20.345.060.1–5
Moving/removal	If a nonconforming structure is moved/removed it loses legal nonconforming status	§ 20.345.030.P
Transitional Industrial exception	In Transitional Zones, industrial activities consistent with Initial Zone are not treated as nonconforming	§ 20.235.060.B–C
Variance to reestablish	A Variance may be used to reestablish nonconforming uses consistent with Chapter 20.345	§ 20.525.020.A–D

Checklist — what an applicant must satisfy to preserve or expand a nonconforming use

Document that the use/structure was lawfully established (historic permits, tax records, business licenses) — burden of proof (§ 20.345.030.A) .
Confirm the use or structure is not an illegal use (illegal uses are not eligible for nonconforming protection) (§ 20.345.020; 20.345.070) .
If seeking an expansion: prepare a plan showing the expansion is within 10% (residential) or within administrative/DP limits (10%/20%) and show no loss of required parking — submit necessary permit (Director/DP) and findings (§ 20.345.050) .
If re‑establishing after discontinuance: file an application for extension before the initial 12‑month discontinuance deadline and provide evidence supporting the extension findings (investment, hardship, efforts to re‑establish) — notice to neighbors will be required (§ 20.345.030.L–M) .
If the structure was damaged: obtain building permits within one year and complete construction within 18 months while certifying the prior nonconformity and meeting building codes (§ 20.345.060) .
Coordinate with related reviews where applicable (Design Review, ADA, Parking, Fire/Building) — nonconforming relief does not waive other code obligations; obtain required permits and compliance certifications (see related chapters) (§ 20.345.050.C.6; 20.500) .
If proposing a Variance to reestablish or expand beyond numeric caps, include variance justifications tied to the uniqueness of the parcel and the public interest (§ 20.525.020) .

Risks & Ambiguities

Issue	Why it matters	What to verify
Legal establishment evidence	Without documentary proof, city can deny nonconforming protection and order abatement	Verify permits, business licenses, dated photographs or utility records; owner bears burden (§ 20.345.030.A)
Whether an expansion “increases nonconformity”	The code terminates nonconforming rights if enlargement increases nonconformity outside the allowed procedures	Confirm whether proposed work qualifies under § 20.345.050 caps and whether Director/DP findings can be met (§ 20.345.050)
Interplay with ADU permitting	State ADU law may constrain local denial based on nonconforming zoning conditions; San Marcos references state ADU provisions	Verify whether ADU review disallows conditioning on correcting nonconforming zoning conditions (see San Marcos ADU chapter and State ADU guidance) (Local ADU chapter; ADU handbook)
Time limits after damage	Missing the one‑year permit window or 18‑month completion can extinguish rebuild rights	Confirm dates and secure building permits within one year and complete per § 20.345.060 schedules (§ 20.345.060.1–3)
Moving or removing a structure	Any move/removal (even on-site) voids the nonconforming status	Confirm whether the proposal includes relocation — moving/removal causes loss of nonconforming rights (§ 20.345.030.P)
Transitional industrial parcels	Some industrial activities in Transitional Zones are excluded from Chapter 20.345 — this can change whether a use is nonconforming	Verify whether the parcel is within a Transitional Zone and whether the “Initial Zone” rules apply (§ 20.235.060.B–C)

Plain-English Summary

If your building or business in San Marcos was legal when it was created but no longer complies with today's zoning, you likely can keep using it — but you generally can't make it bigger, move it, or let it sit unused for more than a year without losing that right; limited small expansions and carefully timed rebuilds are allowed under the rules in Chapter 20.345 (§ 20.345.030–060) .

Source References

San Marcos Municipal Code, CHAPTER 20.345 — Nonconforming Uses and Structures: § 20.345.010–070 (Purpose, applicability, restrictions, maintenance, alteration/expansion, damage/reconstruction, abatement) .
San Marcos Municipal Code, § 20.345.050 (Alteration/expansion numeric limits — residential 10%, nonresidential admin 10%, DP 20%) .
San Marcos Municipal Code, § 20.345.060 (Damage and/or destruction; rebuild timing and conditions) .
San Marcos Municipal Code, § 20.345.030.J–M (Discontinuation/abandonment and extension application process; 12‑month rules) .
San Marcos Municipal Code, Chapter 20.235 / Industrial Zones (Transitional Zone exception) § 20.235.060 .
San Marcos Municipal Code, Chapter 20.240 (Public Institutional and Open Space zone purposes) § 20.240.010–030 .
San Marcos Municipal Code, Chapter 20.400 (Specific use standards; examples such as massage, indoor shooting ranges) § 20.400.010–250 .
San Marcos Municipal Code, Chapter 20.525 (Variances — reestablishment of nonconforming uses) § 20.525.020 .
San Marcos ADU chapter and statewide ADU guidance (2025 ADU handbook) — cited where ADU/nonconforming interplay appears; local ADU provisions referenced in Chapter 20.350 and ADU chapter (See ADU chapter and ADU handbook) .

Useful GoCodebook menu pages (first natural mentions in the body above):

San Marcos zoning & planning overview: /us/california/san-marcos
San Marcos Zoning: /us/california/san-marcos/zoning
San Marcos Development Standards: /us/california/san-marcos/development-standards
San Marcos Parking: /us/california/san-marcos/parking
San Marcos Design Review: /us/california/san-marcos/design-review
San Marcos Overlay Districts: /us/california/san-marcos/overlay-districts
San Marcos ADUs: /us/california/san-marcos/adu
San Marcos Variances and Exceptions: /us/california/san-marcos/variances-and-exceptions
San Marcos Landscaping and Screening: /us/california/san-marcos/landscaping-and-screening
California Building Standards Code (Title 24): /us/california/building-codes

Sources

Retrieved passages

San Marcos Zoning Code (§ B) High relevance
San Marcos Zoning Code (Section 20.345.050) High relevance
San Marcos Zoning Code (section shall) High relevance
San Marcos Zoning Code (Section 20.345.040) High relevance
San Marcos Zoning Code (§ B) High relevance
San Marcos Zoning Code High relevance
San Marcos Zoning Code High relevance
CBC § 3 (chapter shall) High relevance
CFC § 20.345.060 (Section 20.345.060) High relevance
San Marcos Zoning Code (Section 20.100.030) High relevance
San Marcos Zoning Code (§ B) Medium relevance
San Marcos Zoning Code (§ 2) Medium relevance
San Marcos Zoning Code (Chapter 20.345) Medium relevance
CFC § 20.360.080 (§ C) Medium relevance

Cited sections

Official San Marcos code library

Frequently asked questions

What counts as a legal nonconforming use in San Marcos?

A legal nonconforming use is one that was lawfully established under the rules in effect at the time it started but that does not conform to the current Zoning Ordinance; the owner must prove the use or structure was legal at establishment to get nonconforming protection (§ 20.345.030.A) .

How long can I stop operating a nonconforming use before I lose the right to resume it?

If a nonconforming use is discontinued for 12 consecutive months, the right to continue that nonconforming use is deemed abandoned; the Director can grant a single extension for up to 12 months in specific hardship or investment circumstances (total discontinuance limit 24 months) (§ 20.345.030.J–M) .

Can I enlarge my nonconforming commercial building?

Possibly, but San Marcos limits enlargements: administrative relief may allow up to 10% floor area increase; a Director’s Permit/DP can allow up to 20% for nonresidential structures if required findings are met and other development standards are satisfied (§ 20.345.050.B) .

If my nonconforming house is damaged in a fire, can I rebuild it?

Yes in many cases: the code allows rebuilding to the pre‑existing building envelope and use if you can certify the prior nonconformity, obtain building permits within one year, and complete construction diligently (typically within 18 months) without increasing nonconformity or reducing required parking (§ 20.345.060.1–5) .

Does moving a nonconforming structure on the same lot preserve its status?

No — the ordinance states that if a nonconforming structure is moved any distance on the site or removed from the site, it loses its nonconforming legal status and the land must be used in conformance with the current Zoning Ordinance (§ 20.345.030.P) .

Can I use a Variance to re-establish a nonconforming use?

Yes — the Variance provisions allow relief for a parcel to address setbacks, parking, and to reestablish nonconforming uses consistent with Chapter 20.345, subject to the variance standards and findings (§ 20.525.020; § 20.345) .

Are industrial uses in Transitional Zones governed by the nonconforming chapter?

The Ordinance says Chapter 20.345 rules do not apply to industrial uses within a Transitional Zone where ongoing industrial activities consistent with the Initial Zone are not treated as nonconforming — verify whether your parcel is in a Transitional Zone (§ 20.235.060.B–C) .

Will a nonconforming zoning condition stop me getting an ADU?

San Marcos follows state ADU law interplay: state law limits local denial of ADUs due to nonconforming zoning conditions in many cases; consult the local ADU chapter and state ADU guidance and verify whether the nonconforming condition actually affects public health/safety or the ADU construction (Local ADU chapter; ADU handbook) .

Who can approve an extension of nonconforming status and what is the timeline?

The Director handles extension requests and must act on a complete application within set timelines; preliminary decisions, neighbor notice, and the 50‑day decision window (with specific hearing and appeal rights) are described in the application process for extension (§ 20.345.030.M; 20.500.030) .

What happens if a nonconforming use changes to another nonconforming use?

Changing from one nonconforming use to another nonconforming use is a ground for abatement: the code states a change has been made from a nonconforming use to another nonconforming use will cause nonconforming protections to cease (§ 20.345.070.A.1) .

Ask about any San Marcos property

Get a cited, plain-English answer on San Marcos zoning, setbacks, FAR, ADUs and permits — for any address.

Start Free Trial