Local zoning · Contra Costa County

Contra Costa County — Nonconforming Uses

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

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Last reviewed: July 6, 2026

Overview

In unincorporated areas of Contra Costa County, “nonconforming uses” are handled by Title 8 of the County Ordinance Code (Divisions 82 and 84). A nonconforming use is a lawful use that existed before current zoning rules took effect but no longer conforms to those rules. Key provisions describe when such uses may continue, when they may be repaired or enlarged, and how special contexts (like the P-1 planned unit district and airport safety zones) alter those rules. For context on how base districts and development rules fit together countywide, see the zoning overview, including Contra Costa County Zoning, Land Use, and Development Standards.

Plain-English anchor: A “nonconforming use” in unincorporated areas is a use that was legal when established but no longer meets today’s zoning; it can usually continue, but repairs, enlargements, or changes are tightly controlled by specific sections in Title 8.

What “nonconforming use” means in Contra Costa County

  • The County defines a nonconforming use as any lawful use existing when Divisions 82 and 84 became effective that does not conform to current provisions. It is not a violation until the use is discontinued or ceases for any reason. See § 82-8.002 .
  • Repairs/rebuilding after damage: If a building/structure “constituting a nonconforming use” is damaged more than 50% of its reasonable market value, it may not be repaired or rebuilt as nonconforming. If a nonconforming land use is interrupted by catastrophe, it may lawfully resume within six months. See § 82-8.004 .
  • Enlargement/extension: An existing nonconforming use may be extended or enlarged only if a land use permit is first obtained. See § 82-8.006 and the permit administration framework in § 82-6.004 (Board of Adjustment administration of land use permits) .

Nonconforming lots and small-lot occupancy

  • The County restricts lot divisions that would create substandard lots unless a variance is granted. See § 82-10.002(a) .
  • “Small-lot occupancy”: A substandard lot may still be occupied by a single-family dwelling if yard/setback standards are met (or a variance is granted) and certain creation-date conditions are met; the Zoning Administrator may require a public hearing to address neighborhood compatibility. See § 82-10.002(c) .
  • If public acquisition reduces lot area but the remainder retains at least 80% of the required area, the remainder is deemed to have required area; authorized nonconforming area status is preserved under stated thresholds. See § 82-10.004 .

Special contexts that modify nonconforming-use rules

  • P-1 planned unit district (interim): Before a development plan is approved, a legal nonconforming use on a P-1 site may be repaired, rebuilt, extended, or enlarged—but only in accordance with Chapter 82-8 (the nonconforming chapter). See § 84-66.406(2) .
  • Airport approach/turning/transition zones (Buchanan Field): Existing nonconforming structures/trees or uses can continue, but replacements or substantial alterations require a Board of Adjustment permit and cannot become more hazardous to air navigation. See § 86-4.018 (also see airport height/land-use limits in § 86-4.016) .
  • Existing alcoholic beverage sales: Existing licensed alcohol retailers at the effective date are a nonconforming use subject to Chapter 82-8, but also receive “deemed approved” status if they meet performance standards. See § 82-38.402 and cross-reference to § 82-8; standards at § 82-38.808 .
  • Firearms sales: Existing legal nonconforming firearms sales had to document nonconforming status and obtain a dealer license; any increase/expansion requires a land use permit. See § 82-36.204 .

ADUs on properties with legal nonconforming primary units

  • If the primary dwelling is a legal nonconforming unit, an ADU/JADU may be constructed only if the nonconformity is not expanded and the ADU/JADU meets current zoning and building standards. See § 82-24.018 .
  • State law further limits local denial based solely on nonconforming zoning conditions where they do not pose a health/safety threat and are unaffected by the ADU project; see the state summary for context. See HCD’s 2025 ADU Handbook discussion of nonconforming zoning conditions (Gov. Code §§ 66322(b), 66323(c), 66313(h)) . For broader ADU content, see California ADU law.

How this plays out by district/overlay in unincorporated areas

Below are the local districts/overlays that most often trigger nonconforming-use questions for homeowners and small businesses. For full base-district rules and measurements, refer to Contra Costa County Zoning and Development Standards. Related discretionary steps may involve Design Review and Parking compliance.

R-6 Single-Family Residential District

  • Purpose and where it applies: The R-6 district is a single-family residential base district applied on the County zoning map for low-density neighborhoods in unincorporated areas. “Where it applies” parcel-by-parcel is map-based. Not found in retrieved materials (map narrative). Verify with the jurisdiction. See district establishment in § 84-2.004 and R-6 chapter heading in Title 84, Chapter 84-4 .
  • Typical permitted uses: One detached single-family dwelling per lot; crop and tree farming; public parks/playgrounds; small or large family child care homes; supportive housing (≤6 residents); urban farm animal keeping; ADUs/JADUs per Chapter 82-24; other allowances listed in district text. See § 84-4.402 .
  • Key dimensional standards: Not found in retrieved materials. Verify with the jurisdiction.
  • Nonconforming takeaway in R-6: A use that was legal but no longer permitted may continue subject to § 82-8; any enlargement requires a land use permit (§ 82-8.006), and rebuild limits apply if damaged >50% (§ 82-8.004) .

P-1 Planned Unit District

  • Purpose and where it applies: P-1 is a planned district used for master-planned development. The zoning map shows where P-1 applies; minimum site areas are set by use type. See § 84-66.602 and related P-1 procedures in § 84-66.1002–1006 .
  • Typical permitted uses: Determined by the approved development plan; prior to plan approval, interim exceptions allow a single-family dwelling on a legal lot and continuation of existing nonconforming uses per Chapter 82-8. See § 84-66.404 and § 84-66.406 .
  • Key dimensional standards: P-1 relies on the adopted development plan; minimum site areas include 5 acres (residential), 10 acres (nonresidential), 15 acres (mixed), and no minimum for certain office uses. See § 84-66.602 .
  • Nonconforming takeaway in P-1: Until a final development plan is approved, a lawful nonconforming use may be repaired, rebuilt, extended, or enlarged, but only per § 82-8 (including permit and rebuild limits). See § 84-66.406(2) .

Airport Approach/Turning/Transition Zones (Buchanan Field) — Overlay

  • Purpose and where it applies: Airport safety overlay areas near Buchanan Field impose height and use limits to protect air navigation. See § 86-4.016 (use restrictions) and height tables in the same chapter. See also § 86-4.018 (nonconforming uses/structures/trees) .
  • Typical permitted uses: Uses permitted by the underlying base district remain, subject to special airport restrictions that prohibit glare, interference, or other aviation hazards. See § 86-4.016 .
  • Key dimensional standards: Height maximums vary by approach/turning/transition zone; examples include 20 ft at 600–1,000 ft from runway ends with step-ups to 150 ft, and 150 ft in turning zones (see height tables). See § 86-4.016 and related height limits in Chapter 86-4 .
  • Nonconforming takeaway in the overlay: Existing nonconforming structures/trees or uses can continue, but any replacement or substantial alteration needs a Board of Adjustment permit and cannot become a greater hazard than before. See § 86-4.018 . For the County’s overlay framework generally, see Overlay Districts.

Existing Alcoholic Beverage Sales — Nonconforming/Deemed-Approved Framework

  • Purpose and where it applies: Existing licensed alcohol outlets in unincorporated areas are treated as nonconforming uses under § 82-8 but also enjoy “deemed approved” status if they meet performance standards. See § 82-38.402 and § 82-38.808 .
  • Typical permitted uses: Retail sale of alcoholic beverages under a state ABC license, subject to deemed approved standards and enforcement provisions. See § 82-38.808 .
  • Key standards: The deemed-approved activity must avoid nuisance conditions and comply with all laws, or it can lose its status and face permit requirements. See § 82-38.808 .
  • Nonconforming takeaway: These outlets continue as nonconforming uses but are actively regulated by deemed-approved standards layered on top of § 82-8 .

Decision-relevant rules at a glance

Topic What the County allows/restricts Code Reference
Definition of nonconforming use Lawful use existing when Divs. 82 & 84 took effect; not a violation until discontinued/ceased § 82-8.002
Rebuild after damage If damage > 50% of reasonable market value, rebuilding as nonconforming is not allowed; resume interrupted land use within 6 months § 82-8.004
Enlargement/extension Allowed only with a land use permit (administered by Board of Adjustment) § 82-8.006, § 82-6.004
P-1 interim exceptions Until a final plan is approved, lawful nonconforming uses in P-1 may be repaired/rebuilt/extended/enlarged per Chapter 82-8 § 84-66.406(2)
Airport overlay Existing nonconforming structures/trees/uses can continue; significant changes require a Board of Adjustment permit and cannot heighten hazards § 86-4.018
Existing alcohol outlets Treated as nonconforming but “deemed approved” if performance standards are met; otherwise subject to permitting/enforcement § 82-38.402, § 82-38.808
Small-lot occupancy A substandard lot may host one single-family dwelling if yard/setbacks met (or variance granted) and creation-date tests are met § 82-10.002(c)
Area reduced by public taking If remainder retains ≥80% of required area, it is deemed to have required area; certain nonconforming statuses preserved § 82-10.004
ADU on nonconforming primary ADU/JADU allowed if nonconformity is not expanded and ADU/JADU meets current standards § 82-24.018

Practical guidance for applicants in unincorporated areas

  • Start with your base district, overlays, and property history: confirm whether the use or structure predates current zoning. See Contra Costa County Zoning and Overlay Districts.
  • If damage occurred, prepare evidence of market value and repair cost to evaluate the 50% threshold under § 82-8.004. Methodology for “reasonable market value” is not specified in § 82-8. Not found in retrieved materials. Verify with the jurisdiction.
  • Considering expansion? Plan for a land use permit under § 82-8.006; be ready to demonstrate compatibility with Development Standards and any objective Parking or Design Review criteria that may apply.
  • In P-1 areas, check whether a final development plan is already approved; if not, § 84-66.406 governs interim nonconforming allowances (still subject to § 82-8).
  • Near Buchanan Field, always confirm airport overlay restrictions; even maintenance may require specific approvals if it changes height or hazard profiles under § 86-4.018.
  • For ADUs on a nonconforming primary home, ensure the ADU itself is fully compliant and does not expand the existing nonconformity under § 82-24.018; state law further limits denials based on unrelated nonconforming conditions (see state ADU guidance) . If building standards are implicated, coordinate early with the California Building Standards Code.

Checklist

  • Confirm property is in unincorporated Contra Costa County and identify base district(s) and any overlays on the zoning map (R-6, P-1, airport zones, etc.).
  • Determine whether the use/structure predates the applicable zoning and meets the definition in § 82-8.002 .
  • If damaged, document market value and repair scope to evaluate the 50% rebuild limitation in § 82-8.004; track the six-month resumption window for interrupted land uses .
  • For any enlargement/extension, prepare a land use permit application per § 82-8.006 and the permit administration framework in § 82-6.004 .
  • If in P-1, verify whether a final development plan is in place; if not, rely on § 84-66.406 for interim nonconforming rules (still subject to § 82-8) .
  • If near Buchanan Field, confirm any airport-zone restrictions and whether a Board of Adjustment permit is required under § 86-4.018 .
  • If the site has a substandard lot, test eligibility for “small-lot occupancy” under § 82-10.002(c) or consider relief via Variances and Exceptions .
  • For ADUs on nonconforming primary units, confirm compliance with § 82-24.018 and state ADU protections against denials based on unrelated nonconforming conditions .

Risks & Ambiguities

Issue Why it matters What to verify
No general “abandonment clock” in § 82-8 § 82-8.002 says protection ends when a use is “discontinued or ceases,” but no time period is specified for voluntary cessation Not found in retrieved materials; ask County staff how they determine discontinuance and evidence thresholds
“Reasonable market value” for the 50% test The rebuild bar in § 82-8.004 turns on market value; valuation method is not specified in § 82-8 Not found in retrieved materials; request the County’s accepted appraisal method for § 82-8.004 cases
Difference between “repair” vs “substantial alteration” in airport zones In airport overlays, substantial changes to nonconforming features need a Board of Adjustment permit Scope of “substantial” and required submittals under § 86-4.018; coordinate with staff early
P-1 interim rights vs. approved plan conditions Interim nonconforming allowances end once a final plan is adopted Confirm status of development plan and applicable conditions under § 84-66.406 and § 84-66.1004
Small-lot occupancy hearings Zoning Administrator may schedule a hearing for compatibility review Check notice/hearing process and any design conditions referenced in § 82-10.002(c); may implicate Design Review
ADUs on nonconforming sites Local and state rules interact; a compliant ADU cannot be denied for unrelated, non-safety nonconformities Confirm local application of § 82-24.018 and HCD guidance (Gov. Code §§ 66322(b), 66323(c))

Plain-English Summary

If your property in unincorporated Contra Costa County has a use that was legal when it started but doesn’t match today’s zoning, you can usually keep using it. But if it’s badly damaged, you may not be able to rebuild it the same way; if you want to enlarge it, you’ll need a land use permit. Special rules apply in the P-1 planned district and near Buchanan Field. ADUs can still be added to a legal nonconforming home if the ADU is fully compliant and doesn’t make the old nonconformity worse.

Source References

Information Gaps

  • District-specific dimensional standards (setbacks, height, coverage) for R-6 and other base districts were not in the retrieved materials. Not found in retrieved materials.
  • A County-wide, explicit “abandonment period” for nonconforming uses beyond catastrophe-related interruptions was not located. Not found in retrieved materials.
  • A formal County methodology for “reasonable market value” under § 82-8.004 was not provided. Not found in retrieved materials.

Sources

Retrieved passages

  • Contra Costa County Zoning Code (Chapter 82-8.) High relevance
  • Contra Costa County Zoning Code (§ 8215) High relevance
  • Contra Costa County Zoning Code (Section 82-28.1202) High relevance
  • CBC § 66321 (§ 66321) High relevance
  • Contra Costa County Zoning Code (§ 8107) Medium relevance
  • Contra Costa County Zoning Code (§ 8214) Medium relevance
  • Contra Costa County Zoning Code (§ 1) Medium relevance
  • Contra Costa County Zoning Code (chapter which) Medium relevance
  • Contra Costa County Zoning Code (article are) Medium relevance
  • Contra Costa County Zoning Code (§ 2) Medium relevance
  • Contra Costa County Zoning Code (§ 66314) Medium relevance
  • Contra Costa County Zoning Code (§ II) Medium relevance
  • Contra Costa County Zoning Code (Chapter 46-10) Medium relevance
  • Contra Costa County Zoning Code (§ 66333) Medium relevance
  • Contra Costa County Zoning Code (§ III) High relevance
  • Contra Costa County Zoning Code (Chapter 82-48.) High relevance
  • Contra Costa County Zoning Code (Chapter 84.30) Medium relevance
  • Contra Costa County Zoning Code (Section 84-24.1202) Medium relevance
  • Contra Costa County Zoning Code Medium relevance
  • Contra Costa County Zoning Code Medium relevance

Cited sections

Frequently asked questions

What is a “nonconforming use” in unincorporated Contra Costa County?

A lawful use that existed before the current zoning took effect but doesn’t meet today’s rules. It isn’t a violation unless and until it’s discontinued or ceases for any reason. See § 82-8.002 .

Can I rebuild a nonconforming building after a fire or disaster?

Only if damage is 50% or less of its reasonable market value; above 50%, rebuilding the nonconforming use isn’t allowed. If a land use is interrupted by catastrophe, it may resume within six months. See § 82-8.004 .

Can I expand a legal nonconforming business or home?

You can only extend or enlarge an existing nonconforming use if you first obtain a land use permit. The Board of Adjustment administers such permits. See § 82-8.006 and § 82-6.004 .

What if my lot is smaller than today’s standards?

A substandard lot may still have one single-family home if yard/setback rules are met (or a variance is granted) and creation-date tests are satisfied. The Zoning Administrator may review neighborhood compatibility. See § 82-10.002(c) .

How do airport-zone overlays affect nonconforming structures near Buchanan Field?

Existing nonconforming structures/trees/uses can continue, but any replacement or substantial alteration needs a Board of Adjustment permit and cannot create a greater hazard to air navigation. See § 86-4.018 (also see § 86-4.016 use restrictions) .

Are existing alcohol retailers treated differently as nonconforming uses?

Yes. They are nonconforming under § 82-8 but are also “deemed approved” if they meet performance standards; violations can trigger enforcement or permitting. See § 82-38.402 and § 82-38.808 .

Can I build an ADU if my primary home is a legal nonconforming structure?

Yes, if you don’t expand the existing nonconformity and the ADU meets all current zoning and building standards. See § 82-24.018; state law also limits denials based on unrelated nonconforming conditions. See HCD handbook summary (Gov. Code §§ 66322(b), 66323(c)) .

In a P-1 district without a final plan, can a nonconforming use change?

Interim exceptions allow repair, rebuilding, extension, or enlargement of a lawful nonconforming use, but only per Chapter 82-8 (including permits and limits). See § 84-66.406(2) .

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