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Local zoning · Contra Costa County

Contra Costa County — Zoning

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

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Quick answer

In unincorporated Contra Costa County, the adopted Zoning Map controls district boundaries (§ 84-2.002). Typical front setbacks are 20 ft in R-6 (§ 84-4.1004) and 25 ft in M-29 and A-2 (§ 84-26.1004; § 84-38.1004). D-1 duplex lots must be at least 8,000 sf (§ 84-22.602), and L‑I lots at least 7,500 sf (§ 84-58.602). New ADUs require 4 ft side and rear setbacks and are ministerially approvable if standards are met (§ 82-24.006; § 82-24.012(h)(3)).

Last reviewed: July 25, 2026 · AI-generated analysis · General information, not legal advice · details

Compiled from Contra Costa County's adopted code with AI research tools and grounded in the sources cited below. Verify with Contra Costa County planning staff before relying on it.

Overview

In unincorporated areas of Contra Costa County, zoning is governed by Title 8 of the County Ordinance Code and the officially adopted Zoning Map. Land is classified into specific base districts and combining districts, and all use and development must conform to those district regulations and the map’s boundaries. The County also applies countywide rules for hillside development, agricultural preserves, and accessory dwelling units where allowed.

The Zoning Map of Contra Costa County is the controlling reference for district boundaries in unincorporated areas; if boundaries are unclear, the County applies map-interpretation rules and, if needed, the Planning Commission determines the location (§ 84-2.002(d), (5)).

Zoning Map and How Districts Apply

  • The County has adopted the official Zoning Map of Contra Costa County; both paper and digital copies are on file with the Community Development Department (§ 84-2.002(a)–(b)).
  • Changes from rezonings are recorded on the map by the Community Development Director (§ 84-2.002(c)).
  • Boundary interpretation rules:
    • Along streets/right-of-way: boundary is the centerline (§ 84-2.002(d)(1)).
    • Along lot lines: boundary follows the property line (§ 84-2.002(d)(2)).
    • If a line divides a lot: scale on the map controls (§ 84-2.002(d)(3)).
    • Minor discrepancies: Director may identify the boundary; remaining uncertainty goes to the Planning Commission (§ 84-2.002(d)(4)–(5)).
  • All land in unincorporated areas is classified into the land use districts established by Division 84, as shown on the Zoning Map (§ 84-2.004).

Key Cross-Cutting Rules That Modify Zoning

  • Hillside development and slope density controls apply on steep terrain and near significant ridgelines. Grading on parcels with average slope over 26% or with significant ridgelines/hilltops requires specific authorization and must meet stated objectives (§ 814-2.1002; § 814-2.204; § 814-2.206). Final slope gradients cannot exceed the critical gradient and must support revegetation and safety (§ 88-11.822). Hillside street design emphasizes minimal grading and a rural character (§ 814-2.808). See also County Development Standards.
  • Agricultural preserves and Williamson Act contracts: The Board may designate agricultural preserves (§ 810-2.202). Preserves must primarily include land for commercial agriculture (§ 810-2.414), and land conservation contracts must restrict uses to those allowed in an agricultural preserve district (§ 810-4.406). Standards for contracts and preserves are uniform and mandatory (§ 810-2.402; § 810-4.402).
  • Cannabis Exclusion (-CE) Combining District applies in specified unincorporated communities (Acalanes Ridge, Alamo, Bethel Island, Blackhawk, Bollinger Canyon, Contra Costa Centre, Knightsen, Sandmound Slough, Saranap) (§ 84-86.204). The -CE overlay governs if it conflicts with an underlying zone (§ 84-86.206). Except as otherwise provided, all underlying uses remain permitted in a -CE area (§ 84-86.210). See Overlay Districts.

Accessory Dwelling Units (ADUs) in Zoning

  • Where allowed: ADUs are permitted on lots in single-family districts (R-6, R-7, R-10, R-12, R-15, R-20, R-40, R-65, R-100), multiple-family districts (M-6, M-9, M-12, M-17, M-29), F-1 Water Recreation, and P-1 planned district for residential uses; also in agricultural districts (A-2, A-3, A-4, A-20, A-40, A-80), subject to any Williamson Act contract limits (§ 82-24.010).
  • Ministerial approval: Applications are approved ministerially if they meet location, development standards, and applicable building/water/sewer requirements (§ 82-24.006(a)). Certain “by-right” internal conversions and small detached ADUs are explicitly ministerial with simplified standards (§ 82-24.006(b)(1)–(4)).
  • Core standards:
    • Size: Detached ADUs generally up to 1,000 sf, or 1,200 sf on lots ≥12,000 sf or in agricultural districts; attached ADUs are similarly limited and may also be capped at 50% of the primary dwelling’s living area, with minimums for 850/1,000 sf depending on bedrooms (§ 82-24.012(a)).
    • Setbacks: Internal conversions need no new setbacks; new detached/attached ADUs not replacing an existing footprint require 4 ft side and rear setbacks; front/height must follow zone rules except where State height limits apply (§ 82-24.012(h)(2)–(4)).
    • Parking: One additional off-street space is generally required, with exceptions; tandem or setback parking may be allowed (§ 82-24.012(i)(1)–(3)). See also County Parking and California ADU law.
    • Process: Ministerial permits require compliance with County building standards; see the California Building Standards Code reference (§ 82-24.006(a)).

District-by-District Standards (Unincorporated Areas)

R-6 Single-Family Residential District

  • Purpose/character: Conventional single-family neighborhood fabric. Uses are established by the R-6 chapter.
  • Typical permitted uses: Not found in source materials (see § 84-4.402).
  • Key dimensional standards:
    • Front setback: 20 ft (§ 84-4.1004).
    • Corner lot second frontage: 15 ft (§ 84-4.1004).
    • Other yards/height: Not found in source materials (see § 84-4.1006; § 84-4.802 by cross-reference).
  • Applicability: Where R-6 is mapped on the Zoning Map in unincorporated areas (§ 84-2.002).

D-1 Two-Family Residential (Duplex) District

  • Purpose/character: Two-family housing on individual lots, with compatibility to nearby single-family districts (§ 84-22.202 by structure; § 84-26.204 is analogous purpose for multifamily).
  • Permitted uses:
    • All R-6 permitted uses (§ 84-22.402(1)).
    • One detached duplex per lot and customary accessory uses (§ 84-22.402(2)).
    • Uses requiring a land use permit: all R-6 LUP uses (§ 84-22.404).
  • Key dimensional standards:
    • Minimum lot area: 8,000 sf (§ 84-22.602).
    • Front setback: same as R-6 (i.e., 20 ft; 15 ft on the secondary corner frontage) (§ 84-22.1004; § 84-4.1004).
    • Side yard: same as R-10 (§ 84-22.1002; numeric standard not in source materials).
    • Rear yard: same as R-6 (§ 84-22.1006; numeric standard not in source materials).
    • Height: same as R-6 (§ 84-22.802; numeric standard not in source materials).
    • Off-street parking: at least two covered spaces per dwelling unit, min. 9 ft x 19 ft each (§ 84-22.1202). See also County Parking.

M-29 Multiple Family Residential District

  • Purpose/character: Higher-density multifamily, with compatibility to nearby single-family areas (§ 84-26.204).
  • Typical permitted uses: Not found in source materials (see § 84-26.202).
  • Key dimensional standards:
    • Front setback: 25 ft (§ 84-26.1004).
    • Other yards/height/lot standards: Not found in source materials.
  • Applicability: Where M-29 is mapped on the Zoning Map in unincorporated areas.

A-2 General Agricultural District

  • Purpose/character: General agriculture; also functions as an open space zoning district when applied per General Plan open space policies (§ 82-2.018).
  • Typical permitted uses: Governed by the A-2 chapter; Williamson Act contracts restrict lands to commercial agriculture and compatible uses (§ 810-4.406; § 810-2.414).
  • Key dimensional standards:
    • Front setback: 25 ft (principal frontage on corners); 20 ft on the other frontage of a corner lot (§ 84-38.1004).
    • Other yards/height/lot standards: Not found in source materials.
  • Applicability: Where A-2 is mapped; confirm if parcel is also in an agricultural preserve or under contract (§ 810-2.202; § 810-2.402).

R-B Retail Business District

  • Purpose/character: Retail/service commercial, with some light industrial-like activities under permits.
  • Uses requiring a land use permit include: lumber yard, cabinet shop, sheet metal shop, animal hospital, kennels, auto body/paint garage, contractor’s yard, apartments (3+ units), certain outdoor retail activities, specified light manufacturing research meeting strict performance standards, single-room occupancy per Chapter 82-48, and commercial cannabis activities per Chapter 88-28 (§ 84-52.404).
  • Key dimensional standards: Not found in source materials for setbacks/heights/lot.
  • Special access control: Adjacent to narrow roads (≤55 ft ROW) next to residential zones, access may require a permit to address traffic/pedestrian impacts (§ 84-52.404(13)).

L-I Light Industrial District

  • Purpose/character: Light industrial uses that avoid significant nuisances or impacts (§ 84-58.202; § 84-58.402).
  • Permitted uses: Light industrial; operations emitting dust/smoke/fumes/noise/brilliant light or offensive impacts may require a land use permit with conditions; examples include hot mix plants, rendering, food processing, tanneries, wineries, breweries (§ 84-58.402).
  • Uses requiring a land use permit: Any uses from residential, retail, neighborhood business, general commercial, agricultural, and forestry recreation districts; commercial cannabis activities per Chapter 88-28 (§ 84-58.404).
  • Key dimensional standards:
    • Minimum lot area: 7,500 sf (§ 84-58.602).
    • Other yards/height: Not found in source materials.

W-3 Controlled Heavy Industrial District

  • Purpose/character: Heavier industrial operations under specific controls (§ 84-60.202).
  • Typical permitted/conditional uses: Governed by the W-3 chapter and Chapter 84-63; details not in source materials (§ 84-60.202).
  • Key dimensional standards: Not found in source materials.

C (Commercial) Districts — Development Plan Requirement

  • Development plan required: No development is lawful in any C district until a development plan has been submitted and approved per Article 84-50.16 (§ 84-54.1602). Coordinate early with County Design Review.
  • Permitted uses/setbacks/heights: Not found in source materials.

-CE Cannabis Exclusion Combining District (Overlay)

  • Coverage: Applies across multiple unincorporated communities listed in § 84-86.204.
  • Priority: Overlay governs over underlying zone if there is a conflict (§ 84-86.206).
  • Permitted uses: Underlying zoning uses remain permitted except as otherwise provided (§ 84-86.210). “Commercial cannabis activities” is as defined in Chapter 88-28 (§ 84-86.208).
  • Practical note: If siting cannabis-related uses, confirm whether § 84-86.212 applies and how it limits activities. Verify with the jurisdiction.

Selected Standards and Where They Apply

Topic / District Core Standard or Allowance Where It Applies Code Reference
Zoning Map controls Map on file; centerline/property line rules; Planning Commission resolves uncertainty All unincorporated areas § 84-2.002(a)–(d)(1)–(5)
R-6 front setbacks 20 ft front; 15 ft on secondary corner frontage R-6 lots § 84-4.1004
D-1 minimum lot area 8,000 sf D-1 lots § 84-22.602
D-1 front setbacks Same as R-6 (20 ft; 15 ft on corner’s second frontage) D-1 lots § 84-22.1004; § 84-4.1004
M-29 front setback 25 ft M-29 lots § 84-26.1004
A-2 setbacks 25 ft principal frontage; 20 ft other corner frontage A-2 lots § 84-38.1004
L-I minimum lot area 7,500 sf L-I lots § 84-58.602
C district development plan Development plan approval required before any development All C districts § 84-54.1602
Hillside grading control Authorization required on avg slope >26% and at significant ridgelines/hilltops Parcels meeting criteria § 814-2.1002
-CE overlay priority Overlay governs if conflict with underlying zone Listed communities § 84-86.206
ADU setbacks 4 ft side/rear for new ADUs not in existing footprint Zones allowing ADUs § 82-24.012(h)(3)
ADU ministerial approval Ministerial if standards met; special by-right cases Zones allowing ADUs § 82-24.006(a)–(b)

Practical Guidance and Tips

  • Start by confirming your parcel’s base district and any combining/overlay designation on the official Zoning Map. Boundary rules in § 84-2.002 help resolve edge cases.
  • In commercial corridors mapped “C,” plan on a formal development plan submittal before any site work (§ 84-54.1602). Coordinate this with County Design Review.
  • If your site is hilly or near a ridgeline, evaluate average slope early. Grading on parcels >26% average slope requires special authorization and design that meets hillside objectives (§ 814-2.1002; § 814-2.206).
  • For ADUs, use the specific size, setback, and parking allowances in § 82-24.012 and the ministerial pathways in § 82-24.006; also confirm any local overlay constraints and California housing laws.
  • Agricultural properties under Williamson Act contracts face additional use restrictions tied to agricultural preserve standards (§ 810-4.406; § 810-2.414). Verify contract status before proposing non-agricultural uses.

Checklist

  • Identify base zoning and any overlays on the official Zoning Map (§ 84-2.002).
  • Confirm district-specific yard, height, and lot standards (e.g., R-6 20 ft front setback, M-29 25 ft front; § 84-4.1004; § 84-26.1004; § 84-38.1004).
  • If in a C district, prepare and submit the required development plan (§ 84-54.1602).
  • If in a -CE area, check cannabis-related limitations; overlay controls conflicts (§ 84-86.204; § 84-86.206; § 84-86.210).
  • For hillside sites (>26% slope or near significant ridgelines), obtain grading authorization and design to hillside standards (§ 814-2.1002; § 88-11.822).
  • For ADUs, verify zone eligibility, size/setbacks/parking, and ministerial path (§ 82-24.010; § 82-24.012; § 82-24.006) and coordinate with Development Standards.
  • Check for agricultural preserve/Williamson Act status and related use restrictions (§ 810-2.202; § 810-4.406).
  • Confirm Parking and any project-level Design Review, Signage, Landscaping and Screening requirements.
  • If standards cannot be met, evaluate relief via Variances and Exceptions. Existing situations may be governed by Nonconforming Uses.

Risks & Ambiguities

Issue Why it matters What to verify
Map boundary uncertainty Can change which standards/uses apply Apply § 84-2.002(d) rules; if still unclear, seek Planning Commission determination (§ 84-2.002(d)(5)).
Split-zoned parcels Different standards on one lot Exact boundary location per map scale (§ 84-2.002(d)(3)).
D-1 cross-references Several D-1 standards defer to R-6 or R-10 Obtain the current R-6/R-10 yard/height values (not in source materials) (§ 84-22.1002; § 84-22.1004; § 84-22.802).
R-B conditional uses Industrial-like uses need LUP and performance controls Scope and conditions in § 84-52.404; traffic access control on narrow roads (§ 84-52.404(13)).
L-I nuisance thresholds Some uses require LUP to avoid nuisances Apply § 84-58.402 criteria; confirm need for LUP (§ 84-58.404).
C district plan requirement Development not lawful without plan Ensure development plan approval under Article 84-50.16 (§ 84-54.1602).
Hillside grading triggers >26% slope triggers special authorization Slope analysis and hillside compliance documentation (§ 814-2.1002; § 88-11.822).
Cannabis in -CE areas Overlay priority can constrain activities Whether § 84-86.212 applies and how; underlying district allowances; Chapter 88-28 definition linkage (§ 84-86.206; § 84-86.208–.210).
Williamson Act constraints Contract may limit non-agricultural uses or ADUs Contract terms and preserve standards (§ 810-4.406; § 810-2.414; § 82-24.010(b)).

Plain-English Summary

In unincorporated areas, the County’s Zoning Map sets your base district and any overlays. Typical residential front setbacks are 20 ft in R-6 and 25 ft in M-29 and A-2. Duplex lots (D-1) must be at least 8,000 sf. Light industrial (L‑I) has a 7,500 sf minimum lot size. Commercial districts require a development plan. Hillside sites with steep slopes need special grading authorization. ADUs are broadly allowed with 4 ft side/rear setbacks when newly built.

Source References

  • § 84-2.002 Zoning map adopted; boundaries and interpretation. https://library.municode.com/ca/contra_costa_county/codes/ordinance_code
  • § 84-2.004 Districts established (Division 84 applies to unincorporated areas).
  • § 84-4.1004 R-6 front and corner setbacks.
  • § 84-22.202; § 84-22.402; § 84-22.404; § 84-22.602; § 84-22.604; § 84-22.606; § 84-22.802; § 84-22.1002; § 84-22.1004; § 84-22.1006; § 84-22.1202 (D-1 district).
  • § 84-26.202; § 84-26.204; § 84-26.1004 (M-29 district).
  • § 84-38.1004 A-2 setbacks.
  • § 84-52.404 R-B uses requiring a land use permit.
  • § 84-54.1602 Development plans required in C districts.
  • § 84-58.202; § 84-58.402; § 84-58.404; § 84-58.602 (L-I district).
  • § 84-60.202 (W-3 district).
  • § 84-86.204; § 84-86.206; § 84-86.208; § 84-86.210 (-CE overlay).
  • § 82-2.018 Open space zoning districts.
  • § 810-2.202; § 810-2.402; § 810-2.414; § 810-4.402; § 810-4.406 (Agricultural preserves; Williamson Act contracts).
  • § 814-2.204; § 814-2.206; § 814-2.808; § 814-2.1002 (Hillside development objectives and restrictions).
  • § 88-11.822 Final slope gradient standards.
  • § 82-24.004; § 82-24.006; § 82-24.010; § 82-24.012 (Accessory dwelling units).
  • § 82-1.032 Definitions (land within the county; nonurban uses).
  • § 82-18.004 Exceptions (visibility at corners).

Sources

Source passages

  • Contra Costa County Zoning Code (§ 84-2.002) High relevance
  • Contra Costa County Zoning Code (§ 84-86.204) High relevance
  • Contra Costa County Zoning Code (§ 84-2.004) Medium relevance
  • Contra Costa County Zoning Code (§ 82-1.032) Medium relevance
  • Contra Costa County Zoning Code (§ 810-4.402) Medium relevance
  • Contra Costa County Zoning Code (§ 84-26.1004) Medium relevance
  • Contra Costa County Zoning Code (§ 88-11.822) Medium relevance
  • Contra Costa County Zoning Code (§ 84-52.404) Medium relevance
  • Contra Costa County Zoning Code (§ 84-54.1602) Medium relevance
  • Contra Costa County Zoning Code (§ 82-24.010) Medium relevance
  • Contra Costa County Zoning Code (§ 810-4.406) Medium relevance
  • Contra Costa County Zoning Code (§ 814-2.204) Medium relevance
  • Contra Costa County Zoning Code (§ 84-58.202) Medium relevance
  • Contra Costa County Zoning Code (§ 82-24.004) Medium relevance
  • Contra Costa County Zoning Code (§ 82-18.004) Medium relevance
  • Contra Costa County Zoning Code (§ 84-4.1004) Medium relevance

Cited sections

Frequently asked questions

What can I build on an R-6 lot in unincorporated Contra Costa County?

R-6 is a single-family district. The code sets a front setback of 20 ft (15 ft on the secondary frontage of a corner lot) (§ 84-4.1004). The list of permitted uses is in § 84-4.402, which is not included in the source materials here—verify permitted uses with the County.

What are the duplex (D-1) requirements?

D-1 allows a detached two-family dwelling (duplex) and the same permitted uses as R-6 (§ 84-22.402). Minimum lot area is 8,000 sf (§ 84-22.602). Front setbacks match R-6 (20 ft; 15 ft secondary corner frontage) (§ 84-22.1004; § 84-4.1004). Side and rear yards cross-reference R-10 and R-6 standards, respectively; confirm the numeric values (§ 84-22.1002; § 84-22.1006).

What are the multifamily (M-29) setbacks?

In M-29, the required front setback is 25 ft (§ 84-26.1004). Other dimensional standards and permitted uses are governed by the M-29 chapter; details are not in the source materials provided (§ 84-26.202; § 84-26.204). Verify with the County.

Are ADUs allowed and what setbacks apply?

Yes. ADUs are allowed on lots in many residential and agricultural zones (§ 82-24.010). Ministerial approvals are available if standards are met (§ 82-24.006). New ADUs not in an existing footprint must observe 4 ft side and rear setbacks; internal conversions have no new setback requirement (§ 82-24.012(h)(2)–(3)).

Do commercial projects need a special plan?

Yes—no development is lawful in a C (commercial) district until a development plan is submitted and approved per Article 84-50.16 (§ 84-54.1602). Coordinate this requirement early in your entitlement strategy.

How does the Cannabis Exclusion (-CE) overlay affect my property?

The -CE combining district applies in specified unincorporated communities (§ 84-86.204). If there’s a conflict between -CE requirements and the underlying zone, -CE controls (§ 84-86.206). Underlying uses generally remain permitted unless otherwise provided (§ 84-86.210). Confirm any specific prohibitions in § 84-86.212 (not in source materials).

What are A-2 (General Agricultural) setbacks?

Any structure in A-2 must be set back 25 ft from the front; on a corner lot, the principal frontage is 25 ft and the other frontage is 20 ft (§ 84-38.1004). Lands under agricultural preserve or Williamson Act contracts have additional use restrictions (§ 810-2.414; § 810-4.406).

What’s required for grading on steep hillside parcels?

Parcels with average slope over 26% or with significant ridgelines/hilltops cannot be graded without specific authorization, and grading must meet hillside objectives (§ 814-2.1002; § 814-2.206). Final slope gradients must not exceed the critical gradient and must support revegetation and safety (§ 88-11.822).

What’s allowed in L-I (Light Industrial)?

Light industrial uses are allowed; operations with potential nuisances (e.g., emissions, brilliant light) may require a land use permit with conditions (§ 84-58.402). Some uses from other districts are allowed with a land use permit, and the minimum lot area is 7,500 sf (§ 84-58.404; § 84-58.602).

Can I do apartments or kennels in an R-B (Retail Business) area?

Certain uses in R-B require a land use permit, including apartments with three or more units, kennels, contractor’s yards, and specified manufacturing research uses meeting performance standards (§ 84-52.404). Traffic-related access controls may apply where R-B abuts residential across narrow roads (§ 84-52.404(13)).

General information, not legal advice.

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