Local zoning · Colusa

Colusa — Nonconforming Uses

Q: What is a "nonconforming use" in Colusa and where is it defined?

A nonconforming use in Colusa is a use of land or a building that was lawful when established but no longer conforms to current zoned uses; the definition appears in the code definitions under Nonconforming use and Nonconforming building , and the governing rules are in Article 35 (see § 35.01 for continuation and definitions) .

Q: Are outdoor commercial or industrial uses treated differently?

Yes. Nonconforming commercial and industrial uses operated on open land not accessory to a permanent building may be continued for no longer than five years after becoming nonconforming (§ 35.01(a)) .

Q: Can a nonconforming use convert to another nonconforming use?

Yes — if no external structural alterations are made, a nonconforming use of a building may be changed to another nonconforming use of the same or a more restricted classification (§ 35.02) .

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

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Last reviewed: July 1, 2026

Overview

This page explains how the City of Colusa treats nonconforming uses, nonconforming buildings, and nonconforming lots under the local zoning ordinance (commonly called Title 17). It summarizes the code rules that control whether a previously lawful use may continue, when it must convert or terminate, and what triggers loss of nonconforming status. For city-wide background see the Colusa zoning & planning overview and the Colusa Zoning menu.

Important: every rule cited below comes from the Colusa Zoning Code; where the ordinance text did not answer a practical question I note that it is "Not found in retrieved materials" or flag "Verify with the jurisdiction".

How to read this page

Bolded district names and numeric standards are called out so you can find the precise rules (for example R-1, 35.01, 5 years).
The first natural mention of related topics is hyperlinked to the Colusa site menus: setbacks and development standards, parking, design review, overlays, ADUs, and the California Building Standards Code are linked where they are first mentioned in the text.

Key city rules (what the Colusa code says)

The City’s nonconforming-use rules are codified in Article 35 (Nonconforming Uses). The ordinance defines nonconforming use and nonconforming building and sets the primary rules on continuation, abandonment, alteration, destruction, and district-specific amortization (§ 35.01–§ 35.05) .
Continuation: A lawful use existing when the ordinance took effect may continue, but there are express limits (for example, certain open commercial/industrial uses on open land are limited to continuation for no longer than five years after becoming nonconforming) (§ 35.01(a)) .
Abandonment: If a nonconforming use is discontinued for six months or more, that is prima facie evidence of abandonment and the property must thereafter be used in conformity with the code (§ 35.01(c)) .
Changes of use: A nonconforming building may be changed to another nonconforming use of the same or more restricted classification if no external structural alterations are made (§ 35.02) .
Alteration and reconstruction: Except when a use permit is approved, a building devoted to a non-permitted use may not be enlarged, extended, reconstructed or structurally altered unless the use is converted to a permitted use; maintenance is allowed up to a monetary/percentage cap (authorized maintenance not to exceed, during a five-year period, fifty percent of the assessed value) (§ 35.03) .
Destruction threshold: If a nonconforming building is destroyed by fire, act of God, etc., to the extent of more than one-half the replacement value, the building and land become subject to current district regulations (i.e., you lose the nonconforming rights) (§ 35.04) .
District changes: The nonconforming-use rules apply to uses that become nonconforming because of later amendments or changes in district boundaries; any amortization time limit dates from the ordinance or boundary-change that first created the nonconforming use (§ 35.05) .
Special category — adult-oriented businesses: Article 27 contains specific amortization and extension procedures for adult-oriented businesses, including a default 5-year termination for nonconforming adult businesses (and a 1-year rule for some annexed properties), and a formal extension/hearing process with findings if the operator seeks more time (Sec. 27.04; extension rules and findings) .
Definitions: The code defines Nonconforming building and Nonconforming use in the definitions article (as a use or building lawfully existing on the effective date that does not conform to the current allowed uses or development standards) (Definitions: Nonconforming building/use) .

District-by-district breakdown

Below are Colusa districts that are directly relevant to nonconformity questions. For each I list the purpose, typical permitted uses, key dimensional standards, and where that district’s rules appear in the code. If you need the full permitted-use lists or full development tables, check the Colusa Zoning and Colusa Development Standards menus.

Note: the nonconforming rules in Article 35 apply across districts; district subsections below quote the district-specific permitted uses and standards that matter for understanding conversion/compatibility.

R-1 — Single-Family Residential (Article 5)

Purpose: Intended for areas subdivided/designed for single-family residential development (§ 5.01) .
Typical permitted uses: One-family dwellings, accessory buildings, small residential care, parks and public uses, secondary dwelling units (ADUs) (subject to ADU rules) (§ 5.02) . See the Colusa ADUs page for ADU specifics.
Key dimensional standards: Lot area 8,000 sq ft, front yard setback 20 ft, maximum building coverage 35%, side and rear yards as specified in § 5.05 (§ 5.05) . For detailed setback and lot standards see Colusa Development Standards.
Where it applies: Residential single-family neighborhoods; Article 35’s age-based removal rule specifically references all "R districts" for amortization of nonconforming buildings (see § 35.01(b)) .

R-3 — High Density / Multifamily Residential (Article 8)

Purpose: Higher-density residential and mixed residential uses (Article 8, Sec. 8.01–8.05) .
Typical permitted uses: Multifamily dwellings, boarding houses; some public uses may require permits (Sec. 8.02–8.04) .
Key dimensional standards: Lot area 6,000 sq ft, front yard setback 20 ft (10 ft in High Density Combining District), building coverage up to 60%, and building height up to 50 ft (4 stories) (Sec. 8.05) .
Where it applies: Higher-density residential corridors; Article 35 rules on alteration and destruction apply to nonconforming buildings here as elsewhere (§ 35.03–§ 35.04) .

C-N — Neighborhood Business (Article 9)

Purpose: Local neighborhood commercial services (Article 9: Regulations generally) .
Typical permitted uses: Retail and service uses tailored to neighborhood needs (see Article 9 for the full list) (Article 9) .
Key dimensional standards: See the specific Article 9 standards; nonconforming commercial uses on open land are treated specially (may be limited to 5 years continuation) (§ 35.01(a)) .
Where it applies: Neighborhood commercial strips and mixed-use parcels; repairs or enlargements of nonconforming commercial buildings require review under § 35.03 .

P-F — Public Facilities (Article 16)

Purpose: Public facilities, utilities, and uses such as schools, parks, public buildings (Sec. 16.01–16.02) .
Typical permitted uses: Public schools, parks, utilities, public buildings; accessory uses incidental to these (Sec. 16.02) .
Dimensional standards: See Article 16 and Article 32 (general rules) for applicable setbacks and lot standards; nonconforming uses there fall under Article 35 rules (Article 16; Article 35) .

O-S — Open Space (Article 17)

Purpose: Conservation, recreation, and limited agricultural/open uses (Sec. 17.01–17.02) .
Typical permitted uses: Trails, parks, crop/tree farming, grazing, conservation uses (Sec. 17.02) .
Dimensional/use notes: Nonconforming open uses (for example, open contractor yards) that are not accessory to a permanent building are subject to Article 35 limits (see § 35.01(a)) .

Decision‑relevant standards (quick reference table)

Topic / Standard	Rule (plain-English)	Code Reference
Continuation of lawful nonconforming use	A lawful nonconforming use can continue, but commercial/industrial open‑land uses not accessory to a building may only continue up to 5 years after becoming nonconforming	§ 35.01(a)
Abandonment presumption	Stopping a nonconforming use for 6 months or more creates a presumption of abandonment and requires conforming use thereafter	§ 35.01(c)
Exchange to another nonconforming use	You may change a nonconforming building to another nonconforming use of the same or more restricted class if no external structural changes are made	§ 35.02
Alteration / enlargement	No enlargement, extension, reconstruction, or structural alteration unless converted to a permitted use—maintenance allowed up to a 5‑year window or 50% of assessed value	§ 35.03
Destruction by disaster	If more than 50% of replacement value is destroyed, nonconforming status ends and current district rules apply	§ 35.04
R‑district age amortization	In all R districts, nonconforming nonresidential buildings must be removed or converted when they reach specified ages by building class (Class I & II: 40 yrs; Class III & IV: 30 yrs; Class V: 20 yrs) — regulation delayed until 20 years after the article’s effective date	§ 35.01(b)
Adult-oriented businesses	Nonconforming adult businesses generally amortize (terminate) in 5 years; owner may apply for extension through a hearing with specific findings	Sec. 27.04

Practical guidance & interpretation (plain-English synthesis)

If your business or building predates a zoning change and is now nonconforming, you can usually keep operating, but:
- Do not make exterior enlargements or structural changes unless you obtain the discretionary permit that allows alteration (see § 35.03) .
- Do not voluntarily discontinue the use for six months or more — that likely ends your legal nonconforming status (§ 35.01(c)) .
- If a nonconforming structure is damaged beyond half its replacement value, you cannot rebuild it as nonconforming — the property must meet current district rules (§ 35.04) .
For open commercial or industrial operations that are not accessory to a permanent building (for example storage yards), expect a five‑year limit on continuation after nonconformity is triggered (§ 35.01(a)) .
Adult‑oriented uses have a specialized amortization and extension process; read Sec. 27.04 early if that applies to you (there is a formal hearing schedule, filing window and variance‑type fee) .
For district‑specific dimensional implications (setbacks, coverage, height) review the district article (for instance § 5.05 for R‑1) and the City’s development standards; nonconforming uses that create conflicts with required setbacks or parking sometimes trigger enforcement actions or required conversions — verify with planning staff (District articles: § 5.05; § 8.05; Article 9; see Colusa Development Standards and Colusa Parking) .

Links to related local menus (first mention):

For general context, see the Colusa zoning & planning overview.
For the full local code and Title 17 context see Colusa Zoning.
For dimensional controls like setbacks see Colusa Development Standards.
For minimum off‑street requirements see Colusa Parking.
For whether a physical change will require discretionary design review see Colusa Design Review.
If an overlay might affect your nonconforming rights see Colusa Overlay Districts.
If you are thinking about converting part of a nonconforming property to an ADU, consult Colusa ADUs and be mindful of state ADU law and local nonconforming rules.
For building‑code references (structural class, replacement value, etc.) consult the California Building Standards Code.

Checklist — what an applicant must satisfy (practical, stepwise)

Confirm whether your use or building was lawful on the ordinance effective date (establish continuous history) — review title deeds, permits, and business licenses. (Definitions: Nonconforming use/building)
Determine if use was discontinued for six months or more (abandonment presumption) (§ 35.01(c))
If you propose exterior structural work, plan for either conversion to a permitted use or obtain a use permit/variance because enlargement is barred for nonconforming uses (§ 35.03)
If the building was damaged, have the building inspector estimate replacement cost to determine the >50% threshold (§ 35.04)
If your nonconforming activity is open commercial/industrial without permanent building coverage, check the 5‑year continuation rule (§ 35.01(a))
If you operate an adult‑oriented business, consider the amortization schedule and apply for extension within the required time window if needed (Sec. 27.04)
Check district standards (setbacks, coverage, height) — if conversion to a conforming use requires building changes, coordinate with Planning and Building (see Colusa Development Standards and California Building Standards Code)
Expect application fees and hearing notices for extensions/variances (fees same as variance; hearing procedures are described in the ordinance) (Sec. 27.04(b); variance rules)

Risks & Ambiguities

Issue	Why it matters	What to verify
Age-based removal in R districts	The code limits how long certain nonresidential buildings in R districts may remain; the rule ties to building class and time since erection	Verify the building class per the Building Code in effect at adoption and compute the age; confirm the ordinance effective date and whether the 20‑year delay applies (§ 35.01(b))
Maintenance cap ambiguity	The maintenance allowance is stated as "during a period of five years, or fifty percent of the assessed value" — how that is applied in practice can be unclear	Verify how the City calculates "assessed value," the five‑year window start date, and whether cumulative work triggers the cap (§ 35.03)
Abandonment presumption (6 months)	The 6‑month rule is a prima facie presumption — it can be rebutted but can also trigger enforcement	Document continuous use to rebut the presumption; get written confirmations (leases, receipts) if use sporadic (§ 35.01(c))
Open‑land commercial/industrial uses 5‑yr limit	Some nonconforming outdoor uses are explicitly time‑limited	Confirm whether your use is "open" vs. accessory to a permanent building; check precise triggering date for the 5‑year clock (§ 35.01(a))
Destruction >50% valuation	The valuation test can cause loss of nonconforming rights following damage	Obtain the building inspector’s replacement‑in‑kind estimate and consider professional appraisal/appeal procedures (§ 35.04)
Adult-business amortization & extension	Special amortization timelines and an extension hearing process apply	If your use falls in Article 27, file extension requests within the code's deadlines and prepare the required findings and financial/investment evidence (Sec. 27.04)

Plain-English Summary

If a use or building in Colusa was legal when the zoning changed, you can often keep it, but you cannot enlarge it or make structural changes without converting to a permitted use or getting a permit; if you stop the use for six months or your building is more than half destroyed, you lose the nonconforming right (§ 35.01–§ 35.04) .

Source References

Colusa Zoning Code — Article 35, Nonconforming Uses: § 35.01 – § 35.05
Colusa Zoning Code — Alteration/Maintenance and Destruction rules: § 35.03; § 35.04
Colusa Zoning Code — Adult-oriented business amortization and extension rules: Sec. 27.04 (Article 27)
Colusa Zoning Code — Definitions (Nonconforming use / Nonconforming building): Definitions article (N.)
Colusa Zoning Code — R‑1 district rules (uses and development standards): § 5.01–§ 5.05
Colusa Zoning Code — R‑3 district rules (uses and development standards): Article 8 (Sec. 8.03–8.05)
Colusa Zoning Code — P‑F and O‑S district rules: Article 16; Article 17
Colusa Zoning Code — ADU article and related local ADU standards: Article 49 (ADU rules) (see Colusa ADUs)

If you need a scanned official copy or the exact code text for a particular §, contact Colusa Planning; for parcel‑specific interpretations, verify with the jurisdiction.

Sources

Retrieved passages

California Building Code High relevance
Colusa Zoning Code (Article 27) High relevance
Colusa Zoning Code (Article 29) High relevance
California Building Code (Article 35.) High relevance
Colusa Zoning Code (Section 34.01) High relevance
Colusa Zoning Code (Section 18008) Medium relevance
Colusa Zoning Code (title which) Medium relevance
CBC § 66314 (§ 66314) Medium relevance

Cited sections

Official Colusa code library

Frequently asked questions

What is a "nonconforming use" in Colusa and where is it defined?

A nonconforming use in Colusa is a use of land or a building that was lawful when established but no longer conforms to current zoned uses; the definition appears in the code definitions under Nonconforming use and Nonconforming building, and the governing rules are in Article 35 (see § 35.01 for continuation and definitions) .

Can I enlarge or remodel a nonconforming building in Colusa?

Not generally. Except where a use permit is approved, a building devoted to a non‑permitted use may not be enlarged, extended, reconstructed, or structurally altered unless converted to a permitted use; routine maintenance is allowed but limited (maintenance up to a five‑year period or 50% of assessed value) (§ 35.03) .

If I stop operating my nonconforming business for a few months, do I lose my status?

Possibly. The code treats discontinuance of a nonconforming use for six months or more as prima facie evidence of abandonment; that would require subsequent use to conform to the ordinance (§ 35.01(c)) .

What happens if a nonconforming building is damaged or burned down?

If a nonconforming building is destroyed by fire, act of God, etc., to the extent of more than one-half the replacement value, then it loses nonconforming status and must be brought into compliance with current district regulations (§ 35.04) .

Are outdoor commercial or industrial uses treated differently?

Yes. Nonconforming commercial and industrial uses operated on open land not accessory to a permanent building may be continued for no longer than five years after becoming nonconforming (§ 35.01(a)) .

My property is in **R-1** but contains a commercial structure built decades ago — will it be allowed to remain?

Article 35 includes an amortization rule for nonconforming buildings in all R districts that ties removal/conversion to the building's age and building class; the code lists ages by class (e.g., 40 years for Class I & II, 30 years for Class III & IV, 20 years for Class V) and notes a delayed effective date for operation of that rule (§ 35.01(b)) — verify building class with the Building Department (§ 35.01(b)) .

Can a nonconforming use convert to another nonconforming use?

Yes — if no external structural alterations are made, a nonconforming use of a building may be changed to another nonconforming use of the same or a more restricted classification (§ 35.02) .

If I run an adult‑oriented business that became nonconforming, how long do I have?

Adult‑oriented businesses are covered by Article 27: in general, nonconforming adult uses may be amortized (terminated) within five years of the ordinance, with special rules for annexed properties and a formal extension/hearing process if you apply (Sec. 27.04) .

Does the City allow fixing code violations to build an ADU on a nonconforming lot?

The Colusa ordinance contains an ADU article; state ADU rules also constrain local requirements. The local ADU section addresses lot coverage and compatibility; for how nonconforming zoning conditions interact with ADU approval, check the ADU article and consult planning staff (local ADU specifics are in Article 49 and the Colusa ADUs menu) .

If I need an exception, how do I apply for one?

Requests that effectively alter development standards are handled through variances or use permits; Article 15/16/34 and the variance rules set the public hearing and finding requirements. For adult‑use extensions the planning commission/hearing protocols and fees are specified in Sec. 27.04 .

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