Local zoning · Trinity County

Trinity County — Nonconforming Uses

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

Last reviewed: July 6, 2026

Overview

This page explains how Trinity County’s Title 17 Zoning Ordinance treats legally established uses, buildings, and parcels that no longer meet current zoning rules in the unincorporated areas. It covers continuation, limits on enlargement, rebuilding after damage, loss of status through discontinuance, and “nonconforming lots of record.” All citations below are to Trinity County’s Title 17 Zoning Ordinance, which the County formally cites as “The Zoning Ordinance of the County of Trinity.”

Key rule: If a nonconforming use of land or a conforming building is discontinued for a continuous period of one year, it is presumed abandoned and any future use must comply with current zoning. See § 17.33.060.

How Trinity County defines and treats nonconformities

Definition. A “nonconforming” building, structure, or use was lawful when established but no longer conforms to one or more current zoning provisions. See § 17.33.010.
Continuation of nonconforming uses of land. May continue, be transferred, or sold; but cannot be enlarged or extended to occupy more area than before becoming nonconforming. A use that now requires a use permit is nonconforming until a permit is secured per Chapter 17.32. See § 17.33.020 and Chapter 17.32.
Nonconforming buildings.
- Enlargement/alteration. If nonconforming only as to height or setbacks, enlargement or reconstruction may be allowed if new work fully complies with all other provisions and does not encroach further into setbacks. See § 17.33.030(A).
- Maintenance/repairs. Allowed up to 15% of appraised value (per assessor) in any one-year period, with no structural changes. See § 17.33.030(B).
Nonconforming use in a conforming building.
- Expansion within the building may occur only with a use permit (§ 17.33.040(A)); changes to a use of the same or more restricted nature are allowed (§ 17.33.040(B)).
Restoration after damage.
- ≤50% replacement value: may be restored and the use continued if building permits are obtained within 12 months and the reconstructed building has no greater floor area. See § 17.33.050(A).
- 50% replacement value: a use permit is required, with findings that the prior nonconformity was not a nuisance and will not be detrimental; the hearing/procedure tracks Chapter 17.32. See § 17.33.050(B).
Loss of status (abandonment). One year of discontinuance presumes abandonment; future use must comply with current district regulations. See § 17.33.060.
Single-family residence carve-out. For a legally established, nonconforming single-family residential use, only the abandonment rule in § 17.33.060 applies. See § 17.33.070.
Nonconforming lots of record (countywide). Parcels not meeting current access/area/width can still be lawful building sites if they satisfy listed criteria, including creation by an approved subdivision map, a legally created deed before a rezoning that caused nonconformity, or a lot line adjustment. See §§ 17.33A.005–.030.

For how these rules intersect with base zoning and allowable uses, see the County’s zoning and land use pages. Dimensional limits that often drive nonconformities (e.g., setbacks, height) are summarized under development standards. Expansions or substitutions that require a use permit follow Chapter 17.32 processes; note that building permits cannot be issued while a use-permit hearing or appeal is pending (§ 17.32.130).

Key rules at a glance

Topic	What Trinity County allows or prohibits	Code Reference
Definition of nonconformity	Lawful when established; now conflicts with one or more provisions	§ 17.33.010
Continue nonconforming use of land	May continue/transfer/sell; no enlargement or extension to greater area	§ 17.33.020
Uses needing a use permit	Considered nonconforming until a use permit is obtained (Chapter 17.32)	§ 17.33.020; Ch. 17.32
Nonconforming building: additions	Allowed if nonconforming only for height/setbacks and no further encroachment	§ 17.33.030(A)
Nonconforming building: maintenance	Normal maintenance/repairs ≤15% appraised value per year; no structural change	§ 17.33.030(B)
Nonconforming use in conforming building: expand within building	Allowed only with a use permit	§ 17.33.040(A)
Substitute use	May change to a use of the same or more restricted nature	§ 17.33.040(B)
Rebuild after damage ≤50%	Restore and continue use with permits within 12 months; no greater floor area	§ 17.33.050(A)
Rebuild after damage >50%	Requires use permit + findings; procedures per Chapter 17.32	§ 17.33.050(B)
Abandonment	1-year discontinuance presumed abandonment	§ 17.33.060
Single-family exception	Only the abandonment rule applies	§ 17.33.070
Nonconforming lots of record	May be lawful building sites if meet listed criteria	§§ 17.33A.005–.030

District-by-district notes (unincorporated areas)

Countywide (all base districts under Title 17)

Purpose. Chapter 17.33 establishes uniform rules for nonconforming uses and structures applicable across all zones in the unincorporated areas. See §§ 17.33.005–.070.
Practical effect. You may generally continue a lawful nonconforming use, keep and maintain a nonconforming building within limits, and rebuild subject to the 50% threshold and timing, but you cannot enlarge a nonconforming use of land or worsen a setback encroachment without satisfying the standards summarized above. See §§ 17.33.020–.050.
Where it applies. All unincorporated zoning districts administered under Title 17 Zoning. For discretionary approvals that touch nonconformities, see design review and variances and exceptions where relevant.

R-D-1 Recreation Development District

Purpose. The R-D-1 district regulates the Trinity Unit of the Whiskeytown–Shasta–Trinity National Recreation Area, balancing recreation and resource conservation. See § 17.26.008.
Typical permitted uses. Uses allowed by Chapter 17.26; the development standards reference residential, commercial, and industrial categories reflected in minimum building-site sizes. See § 17.26.010 and § 17.26.030. Not found in retrieved materials (full permitted-use list).
Key dimensional standards.
- Minimum building site: residential 0.5 acre; commercial 1 acre; industrial 3 acres (§ 17.26.030).
- Min lot width: 150 ft (§ 17.26.040).
- Height: 2 stories, max 40 ft (§ 17.26.060).
- Setbacks: front 150 ft from road centerline (20 ft within a subdivision or commercial area); side 10 ft; rear 20 ft (§§ 17.26.070–.090).
- 300 ft from reservoir high-water line, with limited exceptions (§ 17.26.100).
District-specific nonconforming rules (§ 17.26.100(B)).
- Nonconforming signs: may be maintained for two years after effective date of Title 17.
- Nonconforming commercial/industrial uses: must be discontinued within 10 years after the effective date; may be extended by the Board of Supervisors to allow amortization of pre–Nov. 8, 1965 investments.
- Nonconforming structures (height, location, coverage, setbacks): must be discontinued within 10 years after the effective date; Board may extend for amortization of pre–Nov. 8, 1965 investments.
- Substandard building sites in single ownership on or before Sept. 16, 1967 may be used as a building site.
Where it applies. Unincorporated parcels within the designated recreation area (Trinity Unit). Verify with the jurisdiction for parcel-specific applicability.

Nonconforming lots of record (countywide)

A parcel that does not meet current access, area, or width may still be a lawful building site if it meets any of the following (§§ 17.33A.005–.030):

Approved subdivision: created through a subdivision approved under the Trinity County Subdivision Ordinance or other applicable regulations at the time (§ 17.33A.010).
Legally created by deed: under one ownership, of record, legally created by recorded deed prior to the zoning enactment that made it nonconforming (§ 17.33A.020).
Lot line adjustment: parcel configuration/size resulted from a boundary line adjustment per the subdivision ordinance (§ 17.33A.030).

Interactions with permits and related topics

Use permits. Expansions or substitutions that require a use permit must follow Chapter 17.32 procedures; permit issuance is paused during hearings/appeals (§ 17.32.130). See Trinity County Zoning for process context.
Development standards. Any new work on a nonconforming building must meet current development standards (e.g., height, setbacks) except where Chapter 17.33 expressly allows retention of existing encroachments.
Overlays and special districts. Overlay rules (e.g., Overlay Districts) can add constraints; R-D-1 includes its own nonconforming timelines summarized above (§ 17.26.100(B)).
Signs. Where a district sets nonconforming sign timelines (as in R-D-1), confirm with Signage if applicable. § 17.26.100(B)(1).
Design review and site work. Additions that bring a project into discretionary review may trigger design review and landscaping and screening standards, in addition to parking.
State ADU law. For ADUs, state law limits a county’s ability to require correction of nonconforming zoning conditions unless a health/safety threat is created by the ADU project; see HCD guidance (Gov. Code §§ 66322–66323) summarized in the 2025 ADU Handbook. Verify any ADU-specific questions with the County and California ADU law.

Checklist

Confirm the use/building/lot was lawful when established (keep dated permits, approvals, assessor records).
Determine whether the nonconformity is a use of land, a building nonconformity (e.g., setbacks), or both (§§ 17.33.020–.030).
If expanding a nonconforming use within a building, apply for a use permit (§ 17.33.040(A)); do not enlarge a nonconforming use of land (§ 17.33.020).
For nonconforming buildings, keep repair/maintenance within the 15% annual cap unless fully compliant (§ 17.33.030(B)).
If damaged, document extent of damage; follow ≤50% or >50% pathways in § 17.33.050, including 12‑month permit timing.
Avoid lapses: maintain continuous operation/use to prevent the 1‑year abandonment presumption (§ 17.33.060).
For substandard parcels, verify eligibility as a nonconforming lot of record (§§ 17.33A.005–.030).
In R-D-1, check the district’s special amortization/discontinuance rules (§ 17.26.100(B)).

Risks & Ambiguities

Issue	Why it matters	What to verify
Proving “lawfully established”	Nonconforming protections hinge on legality at inception	Gather historic permits, approvals, and assessor data; confirm with Planning (§ 17.33.010).
“15% of appraised value” cap	Exceeding the cap can forfeit protections	Confirm the current appraised value basis and scope of work (§ 17.33.030(B)).
Extent of “>50% damage”	Triggers use-permit and findings pathway	How “replacement value” is determined and by whom (§ 17.33.050(B)).
One-year discontinuance	Loss of status if presumed abandoned	Track operational continuity; clarify what counts as discontinuance for your use (§ 17.33.060).
SFR exemption scope	Only the abandonment rule applies to SFR uses	Whether a specific SFR qualifies as “legally established” (§ 17.33.070).
R-D-1 amortization dates	Legacy timelines may affect old signs/uses/structures	Whether a site falls in R-D-1 and whether any extensions were granted (§ 17.26.100(B)).
Permit timing during appeals	Building permits paused during use-permit hearings/appeals	Project schedule implications (§ 17.32.130).

Plain-English Summary

If your use or building in the unincorporated areas was legal when created but doesn’t meet today’s rules, Trinity County generally lets you keep it, maintain it within limits, and sometimes rebuild it after damage. But you can’t expand a nonconforming use onto more land, worsening a setback is off-limits, a long pause can cost you rights after one year, and bigger changes usually require a use permit. Special rules apply in the R‑D‑1 recreation district and for older, legally created small lots.

Source References

Trinity County Title 17 Zoning Ordinance — reference and naming: § 17.39.010.
Nonconforming uses and buildings: §§ 17.33.005–.070.
Use permits and procedures: Chapter 17.32 (including § 17.32.130).
Nonconforming lots of record: §§ 17.33A.005–.030.
R-D-1 district standards and nonconforming timelines: §§ 17.26.008, 17.26.030–.100 (notably § 17.26.100(B)).
State ADU law on nonconforming conditions: 2025 California ADU Handbook summary (Gov. Code §§ 66322–66323).

Sources

Retrieved passages

Trinity County Zoning Code (Chapter 17.33) High relevance
Trinity County Zoning Code (title may) High relevance
Trinity County Zoning Code (Chapter 17.30E) High relevance
Trinity County Zoning Code (Chapter 17.30) Medium relevance
Trinity County Zoning Code (Chapter 17.31) Medium relevance
Trinity County Zoning Code (section shall) Medium relevance
Trinity County Zoning Code (§ 66314) Medium relevance
CBC § 66314 (§ 66314) Medium relevance

Cited sections

Official Trinity County code library

Frequently asked questions

How does Trinity County define a nonconforming use or building?

A nonconformity is a building, structure, or use that complied with the rules when established but no longer meets one or more current zoning provisions. See § 17.33.010.

Can I expand a nonconforming use of land in unincorporated Trinity County?

No. You may continue, transfer, or sell it, but you cannot enlarge or extend it to occupy more area than before it became nonconforming. See § 17.33.020.

My building encroaches into a setback. Can I add on?

Possibly. If the building is nonconforming only as to height or setbacks, the County may allow enlargement if the new work meets all other rules and does not encroach further into the setback. See § 17.33.030(A).

What if a nonconforming building is damaged by fire?

If damage is 50% or less of replacement value, you may restore and continue the use by getting permits within 12 months and not increasing floor area. If more than 50%, you’ll need a use permit and specific findings. See § 17.33.050.

How long can a nonconforming use sit idle before I lose it?

One year. If discontinued for a continuous year, it’s presumed abandoned and future use must comply with current zoning. See § 17.33.060.

Are single-family homes treated differently?

Yes. For a legally established, nonconforming single-family residential use, only the abandonment rule applies (the 1‑year discontinuance test). See § 17.33.070.

Can I expand a nonconforming use within a conforming building?

Only with a use permit. The County may allow the nonconforming use to extend throughout the building if a use permit is approved. See § 17.33.040(A) and Chapter 17.32.

My parcel is smaller than today’s minimum. Can I still build?

Possibly. A “nonconforming lot of record” can be a lawful building site if it meets criteria such as creation by an approved subdivision, a legally recorded deed prior to the rezoning that created the nonconformity, or a lot line adjustment. See §§ 17.33A.005–.030.

Are there districts with special nonconforming timelines?

Yes. In the R‑D‑1 Recreation Development District, nonconforming signs, uses, and structures are subject to legacy amortization/discontinuance timelines tied to the ordinance’s effective date, with limited extensions by the Board. See § 17.26.100(B).

Do state ADU rules override zoning nonconformities?

In part. For ADUs, the County generally cannot require correction of nonconforming zoning conditions unless the ADU creates or relates to a health/safety threat. See the 2025 ADU Handbook (Gov. Code §§ 66322–66323). Verify with the County.

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