Local zoning · Tuolumne County

Tuolumne County — Nonconforming Uses

Q: What is a nonconforming use in Tuolumne County?

A nonconforming use in Tuolumne County is a land use or structure that was lawfully established prior to an amendment or adoption of Title 17 that makes the use or structure no longer conform to current zoning regulations; the local definition is § 17.04.2550 and Chapter 17.32 implements its treatment.

Q: Are nonconforming agricultural uses treated differently?

Yes. § 17.32.060 specifically addresses nonconforming agricultural land uses and allows certain enlargements (up to 10% more area for the agricultural use) and requires Director approval for changes between nonconforming agricultural uses.

Nonconforming Uses under the Tuolumne County local zoning and planning code, with the controlling citations.

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Last reviewed: July 3, 2026

Overview

This page explains how Tuolumne County regulates nonconforming uses, nonconforming structures, and nonconforming parcels in the unincorporated areas under Title 17 (Zoning). The rules are in Chapter 17.32 (Nonconforming Uses) and are applied together with the general development standards in Chapter 17.22; the Code’s intent is to allow lawful pre-existing uses to continue in a limited way while encouraging gradual elimination of nonconformities. See the County overview for zoning context here: Tuolumne County zoning & planning overview and the County Zoning menu for district-level rules: Tuolumne County Zoning.

Chapter highlights used on this page (cite each where used):

Purpose and general rules: § 17.32.010.
Applicability (when a use/structure becomes nonconforming): § 17.32.020.
Repairs & structural alteration limits: § 17.32.080.
Restoration/reconstruction after damage: § 17.32.090 (two‑year rebuilding window; 18‑month abandonment rule referenced): § 17.32.090.
Agricultural exceptions: § 17.32.060.
Limited enlargement allowance and parcels of record: § 17.32.110.
Definition of “Nonconforming use”: § 17.04.2550.
Relevant development standards used to test nonconformity (setbacks, heights): § 17.22.020 and § 17.22.030.

How Tuolumne County treats nonconformities (plain-English rules tied to the Code)

The Code’s purpose is to allow legal pre‑existing uses and structures to continue, but not to expand indefinitely; Chapter 17.32 formalizes that approach (§ 17.32.010) and applies when a change in the zoning district or ordinance creates the nonconforming condition (§ 17.32.020) .
Basic limits:
- Ordinary maintenance and repairs are allowed; but structural alterations are limited except where the Code expressly allows them (§ 17.32.080) .
- If a nonconforming structure is damaged, the County allows restoration/reconstruction in-place without increasing height or size (subject to limits) if reconstruction starts within two years; abandonment and thresholds are controlled by the Code (§ 17.32.090) .
- Nonconforming nonresidential uses may be expanded only within narrow limits (see the one-time 10%/1000 sf allowance below) and some categories (like agriculture) have tailored exceptions (§ 17.32.110, § 17.32.060) .
Where a parcel of record is smaller than a district minimum, it may still be used as a building site if all other standards (setbacks, parking, etc.) can be met (§ 17.32.110) .
The County cross‑references other chapters for abandonment procedures and compatibility (for example, airport compatibility) — verify with the Director for parcel‑specific questions (§ 17.32.050 and airport combining provisions).

Note: the zoning Code applies only to the unincorporated areas of Tuolumne County (not to incorporated cities) — the general applicability language is in § 17.02.060.

District-by-district breakdown (how nonconforming rules intersect each district)

Below are the principal districts where nonconforming uses commonly occur. The nonconforming rules in Chapter 17.32 are generally district‑neutral (they apply across districts) but interact with district dimensional standards (setbacks, height, lot size, permitted uses). For the district purpose and permitted uses consult the district chapters in Title 17; the specific development standards you’ll use to test nonconformance are in § 17.22.020 (height) and § 17.22.030 (setbacks).

AE-160, AE-80, AE-37 (Exclusive Agricultural / Agricultural Estate districts)

Purpose: protect agricultural production and open‑space agriculture; allow accessory agricultural uses and limited guest/visitor activities as in the land‑use tables. Agriculture-specific allowances and screening rules are common. See Article 2, Chapter 17.10 for full land‑use tables.
Typical permitted uses: farming, accessory storage and agricultural buildings, limited guesthouses (on larger parcels) — accessory uses shown as “P” in the AE land‑use table.
Key dimensional standards (that determine nonconformance): height and setback limits from § 17.22.020 and § 17.22.030 (apply unless a combining district modifies them). Nonconforming agricultural uses have a special rule allowing up to 10% expansion of area occupied by the agricultural use (see § 17.32.060).
Where it applies: unincorporated agricultural lands in Tuolumne County (see Chapter 17.10).

A-20, A-10 (Agricultural / Large‑lot residential)

Purpose: rural residential on large parcels with agricultural uses permitted. Many accessory uses allowed, limited density. See Chapter 17.10.
Nonconforming interaction: similar to AE districts; agricultural exceptions in § 17.32.060 still apply. Height and setbacks per § 17.22.020/030 determine if a building or improvement is nonconforming.

R-1, R-2, R-3, RE-1 (Residential districts)

Purpose: single‑family and multifamily residential uses. See Chapter 17.12 for uses and density.
Typical permitted uses: dwellings, accessory structures, home occupations. If a dwelling or accessory building legally predates current setbacks/heights, it is nonconforming and may be maintained but not substantially altered except as allowed by § 17.32.080 and § 17.32.090. ADU/JADU state rules also limit local denial based on nonconforming zoning conditions — see ADU law guidance and consult the County ADU chapter. For local ADU interactions see the County ADU chapter (Title 17, Chapter 17.36) and State ADU law.

C-K, C-O, C-1, C-2, C-S (Commercial / Mixed‑use districts)

Purpose: commercial activities (neighborhood to regional). See Chapter 17.14 for permitted uses.
Nonconforming interaction: the Code allows limited expansion of nonconforming nonresidential structures by up to 10% of floor area (one-time, subject to Code criteria) — see § 17.32.110. Repairs allowed, but structural alterations are restricted (§ 17.32.080).

BP, M-1, M-2 (Business Park / Industrial)

Purpose: industrial and distribution uses. See Chapter 17.16.
Nonconforming interaction: industrial structures rendered nonconforming by rezoning or ordinance amendment can remain under Chapter 17.32, but rebuilding after destruction follows the same thresholds (75% damage threshold is used to determine partial vs. full destruction in reconstruction rules). Airport compatibility may add constraints.

Combining / Overlay districts — e.g., :AIR (Airport Combining), :HDP (Historic Design Preservation)

:AIR (Airport Combining) — special provisions treat nonconforming uses that become incompatible due to airport compatibility plan changes differently; the Code includes special nonconforming rules within the Airport Combining district and cross references the County airport land use compatibility plan; deed notices are recorded for parcels in the :AIR district. Verify Airport Combining restrictions and consistency review requirements with the Director and the Airport Land Use Commission. (See the Airport Combining provisions in Title 17 and associated sections.)
:HDP / Historic Combining — Historic districts are treated differently for setbacks (historic buildings can be exempt from standard setbacks) and nonconforming signs/structures within a historic district have specific rules; consult Chapter 17.22 (Parcel/Yard Regs) and the Historic Preservation Chapter for details.

Practical note: Chapter 17.32 is a cross‑cutting chapter — it governs how nonconformities are handled regardless of the base district, but district development standards (height, setbacks, permitted uses) are the technical baseline that determine whether something is nonconforming. See the County development standards here: Tuolumne County Development Standards.

Quick table — the most decision‑relevant nonconforming provisions

Issue / Standard	What the Code allows or limits	Code Reference
Definition — what is a nonconforming use	A lawful use/structure existing before a Title 17 change that does not conform to current district rules	§ 17.04.2550
Purpose / general policy	Permit continuation but limit expansion; encourage elimination of nonconformities	§ 17.32.010
Applicability	Applies when zoning changes make a use/structure nonconforming	§ 17.32.020
Repairs & maintenance	Allowed; structural alterations only as permitted by Code	§ 17.32.080
Rebuild after damage	May be restored if reconstruction begins within two years; no increase in height/size except as allowed	§ 17.32.090
Re‑establishment after abandonment	Uses/structures re‑established after abandonment are not to be reestablished except in compliance with the Chapter; abandonment rules cross‑reference Chapter 17.30	§ 17.32.050 (and Chapter 17.30)
Agriculture exception	Nonconforming agricultural uses can be enlarged up to 10% (special rules apply)	§ 17.32.060
Limited enlargement (nonresidential)	One‑time extension/enlargement of total floor area by up to 10% (or specified threshold)	§ 17.32.110
Setbacks / heights (to test nonconformance)	Standard setbacks and heights used to determine conformity: setbacks § 17.22.030, heights § 17.22.020	§ 17.22.030; § 17.22.020
Signs	Legal nonconforming signs may continue but may not be enlarged/altered or reestablished after 18 months or >75% damage	§ 17.34.100 & § 17.34.110

Checklist — what an applicant must satisfy (practical step list)

Confirm the use/structure was legally established before the effective date of the regulatory change; document prior permits, tax records, or other proof (§ 17.04.2550, § 17.32.010)
Verify which nonconforming rule applies (structure vs. use vs. lot) and whether the parcel is in a combining/overlay district (for example, :AIR or :HDP) that imposes additional rules (see the Airport Combining provisions). Verify with the Director.
If proposing reconstruction after damage, document the date/extent of damage and plan to commence reconstruction within the two‑year window where applicable (§ 17.32.090)
If proposing enlargement of a nonresidential nonconforming use, limit the requested increase to the one‑time 10% (or other Code limit) and justify consistency with Chapter 17.32 and the General Plan (§ 17.32.110)
For repairs that could be construed as structural alteration, check § 17.32.080 and get Director approval where required.
If the nonconforming condition relates to setbacks or height, measure against § 17.22.020/030 and determine whether a Use Permit or Minor Modification is required. Reference development standards and parking requirements (parking guidance here) Tuolumne County Parking.
If the parcel is substandard in size but of record, verify you can meet other development standards; the Code allows use of record parcels as building sites if other standards are met (§ 17.32.110)

Risks & Ambiguities

Issue	Why it matters	What to verify
Abandonment timing and evidence	Abandonment rules can extinguish nonconforming rights (18 months is a commonly referenced threshold in reconstruction language)	Verify abandonment rules and evidence standard with the Community Development Director and check § 17.32.050 and related Use Permit abandonment clauses.
Whether a repair is a structural alteration	Alterations beyond routine maintenance can be disallowed	Confirm scope against § 17.32.080 and get Director determination.
“10% enlargement” math and one‑time application	Confusion over what floor area base is used (historic recorded area vs. current)	Provide measured as‑built floor area, reference § 17.32.110, and ask County to confirm baseline.
Airport Combining (:AIR) conflicts	Airport compatibility may prohibit reconstruction even if County rules generally permit it	Check the :AIR provisions and consult the Airport Land Use Commission — Code references airport rules and deed notices.
Interaction with ADU rules and State law	State ADU law limits the County’s ability to deny ADUs solely because of nonconforming zoning conditions	For ADUs/JADUs, confirm interplay with State law and the County’s ADU chapter; State ADU guidance affects how nonconforming zoning conditions are treated. Verify with the Director.
Historic district exemptions	Historic setbacks or design rules may create exceptions that affect nonconforming determinations	If in :HDP or :H, check the Historic Preservation chapter and § 17.22.030 (setbacks exemption).

Plain‑English Summary

If your building or use in the unincorporated areas of Tuolumne County was legal when it was put there but no longer meets today’s zoning rules, Chapter 17.32 mostly lets it stay — you can maintain it and in narrow cases repair or rebuild it — but you generally cannot expand it, reintroduce it after abandonment, or change it to another nonconforming use without following the Code’s limits and getting County approval. Always verify parcel‑specific issues (airport overlay, historic overlay, ADU/state law interactions) with the Community Development Director.

Source References

Tuolumne County Zoning (Title 17), Chapter 17.32 (Nonconforming Uses) — § 17.32.010 et seq.
Tuolumne County Zoning (Title 17), Chapter 17.22 (Standards for All Development and Land Uses) — § 17.22.020, § 17.22.030 (heights and setbacks).
Tuolumne County Zoning (Title 17), Definitions — § 17.04.2550 (Use, nonconforming).
Tuolumne County Zoning — Airport Combining and nonconforming conditions (AIR district provisions referenced in Title 17).
Tuolumne County Zoning — Signs: nonconforming signs § 17.34.100/§ 17.34.110.
Tuolumne County Zoning — Land‑use and district tables (AE, A, residential, commercial columns).

Related internal guidance pages (first mentions of these topics were linked above in the body):

Information Gaps

The uploaded Title 17 excerpts establish the County’s nonconforming rules (Chapter 17.32) and the general development standards (Chapter 17.22), but full district land‑use tables and every district‑specific permitted‑use list (Chapter 17.10, 17.12, 17.14, 17.16) were not fully extracted here for every zoning district; parcel‑level determinations therefore require looking up the full district table for a specific zone. Not found in retrieved materials: full text of every district’s permitted‑use table and any implementing administrative forms/procedures for nonconforming determinations (verify with the Community Development Department).
The County’s published guidance on how the Director applies the abandonment standard (evidence thresholds) is not in the provided excerpts — Verify with the Community Development Department (Director).

Sources

Retrieved passages

Tuolumne County Zoning Code (ARTICLE 3) High relevance
Tuolumne County Zoning Code (Chapter shall) High relevance
Tuolumne County Zoning Code (Chapter shall) High relevance
Tuolumne County Zoning Code (section 18.24.040) High relevance
Tuolumne County Zoning Code (Section 17.32.050) High relevance
Tuolumne County Zoning Code (Chapter 17.58) Medium relevance
Tuolumne County Zoning Code (Title 15) Medium relevance
Tuolumne County Zoning Code (Chapter shall) Medium relevance
Tuolumne County Zoning Code (§ 8) Medium relevance
CBC § 66314 (§ 66314) Medium relevance
Tuolumne County Zoning Code (Chapter shall) Medium relevance
CBC § 8 (§ 8) Medium relevance
CBC § 8 (§ 8) Medium relevance
CBC § 115 (Chapter for) Medium relevance
CBC § 8 (§ 8) Medium relevance
Tuolumne County Zoning Code (Section 17.104.020) Medium relevance

Cited sections

Tuolumne County Zoning (Title 17), Chapter 17.32 (Nonconforming Uses) — **§ 17.32.010** et seq. (Title 17)
Tuolumne County Zoning (Title 17), Chapter 17.22 (Standards for All Development and Land Uses) — **§ 17.22.020**, **§ 17.22.030** (heights and setbacks). (Title 17)
Tuolumne County Zoning (Title 17), Definitions — **§ 17.04.2550** (Use, nonconforming). (Title 17)
Tuolumne County Zoning — Airport Combining and nonconforming conditions (AIR district provisions referenced in Title 17). (Title 17)
Tuolumne County Zoning — Signs: nonconforming signs **§ 17.34.100**/**§ 17.34.110**. (§ 17.34.100)
Tuolumne County Zoning — Land‑use and district tables (AE, A, residential, commercial columns).
Tuolumne County Zoning
Tuolumne County Development Standards
Tuolumne County Parking
Tuolumne County Design Review
Tuolumne County Overlay Districts
Tuolumne County Historic Preservation
California Building Standards Code
California ADU law
TuolumneCounty_ZoningCode.md

Frequently asked questions

What is a nonconforming use in Tuolumne County?

A nonconforming use in Tuolumne County is a land use or structure that was lawfully established prior to an amendment or adoption of Title 17 that makes the use or structure no longer conform to current zoning regulations; the local definition is § 17.04.2550 and Chapter 17.32 implements its treatment.

Can I rebuild a nonconforming building that was damaged by fire?

Yes — the County allows restoration, reconstruction, or replacement of a nonconforming structure in the same location without increasing height or floor area if reconstruction is commenced within two years of the damage; see § 17.32.090 for the precise conditions and exceptions.

Can a nonconforming commercial building be enlarged?

A legally nonconforming nonresidential structure may be enlarged one time by up to 10 percent of its floor area (or by the thresholds stated in the Code) subject to the Chapter’s conditions — see § 17.32.110. Verify with the Community Development Director whether your project qualifies.

Are nonconforming agricultural uses treated differently?

Yes. § 17.32.060 specifically addresses nonconforming agricultural land uses and allows certain enlargements (up to 10% more area for the agricultural use) and requires Director approval for changes between nonconforming agricultural uses.

If my setback is nonconforming, can I alter the structure?

Routine maintenance is allowed, but structural alterations that increase the nonconformity are restricted; setbacks and projection rules are in § 17.22.030 and structural alteration rules are in § 17.32.080 — a Use Permit or other approvals may be required for enlargements or relocations.

How long before a nonconforming use is considered abandoned?

The Code refers to abandonment procedures and cross‑references Chapter 17.30 for abandonment determination, and reconstruction language cites an 18‑month cessation threshold in restoration rules; confirm the application of abandonment rules with the Director on a parcel‑by‑parcel basis (§ 17.32.050 and § 17.32.090).

Do airport overlays affect nonconforming rights?

Yes. The Airport Combining (:AIR) District contains provisions addressing nonconforming conditions created by adoption or amendment of the County airport land use compatibility plan; nonconforming uses in :AIR are subject to special rules and deed notices are recorded for parcels in the :AIR overlay — consult the :AIR provisions and the Airport Land Use Commission for consistency review.

Can I build an ADU if my lot or structure is nonconforming to zoning?

State ADU law limits a local agency’s ability to deny ADU permits because of nonconforming zoning conditions in many situations; consult the County ADU chapter and State ADU rules — and verify with the County — because local ADU procedures may incorporate both Title 17 and State requirements. See the County ADU chapter and State ADU guidance.

What happens to nonconforming signs?

Nonconforming signs legally placed before the current sign rules may continue indefinitely but may not be structurally altered, enlarged, or reestablished after 18 months of discontinuance or after damage exceeding 75% of replacement cost; see § 17.34.100 and § 17.34.110.

Who decides borderline cases (for example, whether a repair is “structural”)?

The Community Development Director and the County’s review authorities administer Title 17; where the Code uses discretionary terms the Director or the Planning Commission (depending on the approving authority) will make the determination — check § 17.02.080 (administration and discretion) and the specific nonconforming provisions. Verify parcel specifics with the Community Development Department.

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