Contra Costa County — Development Standards

Last reviewed: July 6, 2026

Overview

This page distills the site development standards that the Contra Costa County Zoning Ordinance applies in the unincorporated areas. The ordinance organizes rules by district in Division 84, with countywide rules in Division 82 and special provisions in Division 88. Division 82 confirms these titles regulate all private/public uses in the unincorporated territory, not inside incorporated cities (§ 82-2.004 ). For context and broader code navigation, see the zoning overview at Contra Costa County zoning & planning overview and the district list at Contra Costa County Zoning.

Most residential single-family districts in unincorporated Contra Costa County share the same maximum building height of 2.5 stories or 35 ft and draw setbacks by district; appurtenances like chimneys and flagpoles can exceed height limits under § 82-2.008 .

Countywide rules that cut across districts

• Applicability and enforcement. Divisions 82 and 84 apply throughout the unincorporated areas (§ 82-2.004; violations are a public nuisance, § 82-2.006 ).
• How height is measured/exempted. Mechanical appurtenances, chimneys, towers, and similar features are exempt from district height limits (§ 82-2.008 ).
• Front-yard/setback chapter. The code points to district chapters for front yard requirements (§ 82-12 [cross-reference] and “Ch. 84-4 ff.”), so always check the specific district’s chapter (§ 82-12.202 note ).
• Substandard “small lot” relief. A substandard lot can still be occupied by a single-family dwelling if yards/setbacks are met or varied, and the parcel meets the criteria in § 82-10.002(c); the Zoning Administrator may require a compatibility review (§ 82-10.002(c) ).
• Lots split by district lines. The least restrictive district can extend 30 ft over the line (§ 82-10.006 ).
• Utilities & pipelines. Utility rights-of-way are largely exempt from Divs. 82 and 84 except they must meet setback regulations (§ 82-2.010(a) ).
• Airport height overlay. Near Buchanan Field, separate, lower height planes apply by approach/turn/transition zone; many locations are capped well below 150 ft (§§ 86-4.012, 86-4.014 ). See Contra Costa County Overlay Districts.

SB 9 two-unit “Urban Housing Development” (UHD) standards

UHDs are allowed only on specific single-family lots (R-6, R-7, R-10, R-12, R-15, R-20, R-40, R-65, R-100, and P-1 for single-family) and must meet objective standards, including lot coverage tiers: up to 67% (lots <3,000 sf), 50% (3,000–5,999 sf), 40% (6,000–11,999 sf), and 30% (≥12,000 sf), with small-unit allowances beyond these caps for one added unit (e.g., 800/1,000/1,200 sf depending on lot size) (§ 88-36.010; § 88-36.012(d) ). Design submittals are required (§ 88-36.008 ). For discretionary review triggers, coordinate with Contra Costa County Design Review.

ADUs and how they interact with local standards

Accessory dwelling units and JADUs are recognized in several residential chapters (e.g., R‑20 lists ADUs/JADUs; § 84-14.402(9) ). State ADU law requires jurisdictions to allow at least an 800 sf ADU with 4 ft side/rear setbacks, and to avoid lot coverage/FAR limits that would preclude that minimum; detached ADU height is generally 16 ft (with limited increases in specific transit contexts) (Gov. Code §§ 66321–66323; HCD 2025 ADU Handbook ). For a deeper state-law primer, see California ADU law.

District-by-district development standards (unincorporated areas)

Below are the core dimensional controls—lot area/width/depth, setbacks, height, and, where applicable, lot coverage—plus a brief “what’s typical” for uses. All locations are where the County zoning map shows the district in the unincorporated areas; confirm with the Planning Division (§ 82-2.004 ). Where other standards (e.g., parking, signs) apply, they are cited.

R-6 — Single-Family Residential

• Purpose/uses: Single-family homes are the typical use; additional uses may require a land use permit (§ 84-4.404 ).
• Key standards: Min lot area 6,000 sf (§ 84-4.602), min width 60 ft (§ 84-4.604), min depth 90 ft (§ 84-4.606); front setback 20 ft; corner secondary frontage 15 ft (§ 84-4.1004); side yards aggregate 15 ft, min 5 ft each (§ 84-4.1002); rear 15 ft (3 ft for accessory structures) (§ 84-4.1006); max height 2.5 stories or 35 ft (§ 84-4.802) .
• Notes: R‑6 parking is two off-street spaces per unit, outside setbacks; some legacy lots may have reduced minimums (§ 84-4.1202 ). See also Contra Costa County Parking.

R-7 — Single-Family Residential

• Uses: Same as R-6 for permitted and land-use-permit uses (§§ 84-6.402, 84-6.404 ).
• Key standards: Min lot area 7,000 sf (§ 84-6.602); min width 70 ft (§ 84-6.604); depth per R‑6 (§ 84-6.606); front/side/rear per R‑6 (§§ 84-6.1004, 84-6.1002, 84-6.1006); max height per R‑6 (§ 84-6.802) .

R-10 — Single-Family Residential

• Uses: Same as R-6 (§§ 84-8.402, 84-8.404 ).
• Key standards: Min lot area 10,000 sf (§ 84-8.602); min width 80 ft (§ 84-8.604); depth per R‑6 (§ 84-8.606); front per R‑6 (§ 84-8.1004); side yards aggregate 20 ft, min 10 ft each (§ 84-8.1002); rear per R‑6; max height per R‑6 (§ 84-8.802) .

R-12 — Single-Family Residential

• Uses: Same as R-6 (§§ 84-10.402, 84-10.404 ).
• Key standards: Min lot area 12,000 sf (§ 84-10.602); min width 100 ft (§ 84-10.604); min depth 100 ft (§ 84-10.606); front per R‑6 (§ 84-10.1004); aggregate side yards 25 ft, min 10 ft each (§ 84-10.1002); rear per R‑6; max height per R‑6 (§ 84-10.802) .

R-15 — Single-Family Residential

• Uses: Same as R-6 (§§ 84-12.402, 84-12.404 ).
• Key standards: Min lot area 15,000 sf (§ 84-12.602); width/depth/side yards per R‑12; front/rear per R‑6; max height per R‑6 (§§ 84-12.604–.1006, .802) .

R-20 — Single-Family Residential

• Uses: R‑20 permitted/permit uses are listed in Article 84‑14 (e.g., ADUs/JADUs recognized; § 84‑14.402(9)); additional uses may require a permit (§ 84-14.404) .
• Key standards: Min lot area 20,000 sf (§ 84-14.602); min width 120 ft (§ 84-14.604); min depth 120 ft (§ 84-14.606); front 25 ft (corner secondary 20 ft) (§ 84-14.1004); aggregate side yards 35 ft, min 15 ft (§ 84-14.1002); rear per R‑6; max height per R‑6 (§ 84-14.802) .

R-40 — Single-Family Residential

• Uses: Same as R-20 (§§ 84-16.402, 84-16.404 ).
• Key standards: Min lot area 40,000 sf (§ 84-16.602); min width 140 ft (§ 84-16.604); min depth 140 ft (§ 84-16.606); front per R‑20 (§ 84-16.1004); aggregate side yards 40 ft, min 20 ft (reduced accessory side yard if ≥75 ft from front line) (§ 84-16.1002); rear per R‑6; max height per R‑6 (§ 84-16.802) .

R-65 — Single-Family Residential

• Uses: Permitted uses mirror R‑20; some R‑6 special uses are excluded unless permitted (§§ 84‑18.402, 84‑18.404) .
• Key standards: Min lot area 65,000 sf (§ 84-18.602); width/depth per R‑40 (§§ 84‑18.604, ‑18.606); front per R‑20; side per R‑40; rear per R‑6; max height per R‑6 (§§ 84‑18.802, ‑18.1002, ‑18.1004, ‑18.1006) .

R-100 — Single-Family Residential

• Uses: Permitted uses mirror R‑20; land-use-permit uses mirror R‑65 (§§ 84‑20.402, ‑20.404) .
• Key standards: Min lot area 100,000 sf; min width 200 ft; min depth 200 ft; front 30 ft (corner secondary 25 ft); aggregate side yards 60 ft, min 30 ft; rear per R‑6; max height per R‑6 (§§ 84‑20.602–.1006, ‑20.802) .

D-1 — Two-Family Residential

• Uses: Duplex/two-family area type (see ch. 84‑22).
• Key standards: Min lot area 8,000 sf (§ 84‑22.602); width per R‑10 (§ 84‑22.604); depth per R‑6 (§ 84‑22.606); front per R‑6 (§ 84‑22.1004); side per R‑10 (§ 84‑22.1002); rear per R‑6; max height per R‑6 (§ 84‑22.802) .

M-29/M-12/M-9/M-6 — Multiple-Family Residential

• Programmatic standards: M‑29 requires a development plan and sets open area and building spacing: at least 25% landscaped open area (§ 84‑26.1402), and 20 ft between buildings (§ 84‑26.1602) with development plan content spelled out (§ 84‑26.1802) .
• Density/coverage by subdistrict:
  • M‑12: Max 12 units/acre; max lot coverage 25% (§ 84‑29.404) .
  • M‑9: Max 9 units/acre; max lot coverage 25% (§ 84‑30.402) .
  • M‑6: Max 6 units/acre; max lot coverage 25% (§ 84‑31.404) .
• Where it applies: Where mapped in unincorporated areas; project-level plans are routinely required—coordinate early with Contra Costa County Design Review.

C — General Commercial

• Typical uses: Wholesale, warehousing, lumberyards, contractor yards, auto repair, and uses from N‑B/R‑B; apartments (3+ units) by land-use permit (§§ 84‑54.402, ‑54.404) .
• Key standards: Min lot area 7,500 sf (§ 84‑54.602); aggregate side yards ≥10 ft; rear 20 ft (§ 84‑54.1002); front/road setback ≥10 ft (§ 84‑54.1004); height per N‑B (§ 84‑54.802; numeric not found in retrieved materials) .

R-B — Retail Business

• Typical standards: No side yards required; front/road setback 10 ft; height and lot area track N‑B (§§ 84‑52.1002, ‑52.1004, ‑52.602, ‑52.802) .

O-1 — Administrative Office

• Typical uses: Institutional/office, including hospitals, schools, community clubs, etc. (§ 84‑44.402) .
• Key standards: Min lot area 15,000 sf; min width 100 ft; min depth 90 ft; max coverage 35%; max height 35 ft/2.5 stories; aggregate side yards 15 ft (15 ft min where abutting a residential district) (§§ 84‑44.602–.1002, ‑44.608, ‑44.802) .

L-I — Light Industrial

• Typical uses: Light industry with performance standards; some broader uses by land-use permit (§§ 84‑58.402, ‑58.404) .
• Key standards: Min lot area 7,500 sf (§ 84‑58.602); front/road setback 10 ft (§ 84‑58.1004); side yards 10 ft each (§ 84‑58.1002); max height 3 stories (§ 84‑58.802) .

C-M — Commercial Manufacturing

• Typical uses: Heavier commercial/manufacturing with on-site screening; on-site parking/loading in yards allowed with required landscaping (§§ 84‑56.1602, ‑56.1202) .
• Key standards: Min lot width 120 ft and min lot area 40,000 sf (§ 84‑56.602); max coverage 30% (§ 84‑56.604); front setback 50 ft (§ 84‑56.1004); side/rear 20 ft (50 ft when abutting res/ag districts) (§ 84‑56.1002); max height 35 ft/2 stories (§ 84‑56.802) .

A-3 — Agricultural

• Key standards: Residential buildings max 35 ft (other structures: no max) (§ 84‑40.802); front 25 ft, side 25 ft (50 ft to animal structures from residential district), rear 25 ft (§§ 84‑40.1002–.1006) .

A-4 — Agricultural Preserve (Williamson Act)

• Key standards: Min parcel 40 ac (non-prime) or 10 ac (prime); side 50 ft; front 50 ft; rear 25 ft; residential height max 35 ft (no max otherwise) (§§ 84‑42.602–.1206, ‑42.1002) .

F-R — Forestry Recreation

• Typical uses: Parks, summer homes, hotels, recreation camps (§ 84‑32.402) .
• Key standards: Min lot area 0.5 ac and min width 80 ft (§ 84‑32.602); side yards aggregate 35 ft, min 15 ft; front/road setback 25 ft; max height 4 stories or 50 ft (§§ 84‑32.1002–.1004, ‑32.802) .

HE‑C — Housing Element Combining District (overlay)

• What it does: Applies objective standards by assigned density category (low/medium/high; residential or mixed-use). Examples: front 10 ft, side 5 ft, rear 15 ft; max height 35–65 ft depending on category; max coverage 50–70% (§ 84‑92.604) with a development plan required (§ 84‑92.802) .
• Use with care alongside base district: HE‑C combines with the mapped base district; confirm both sets of standards.

Quick-reference standards table (selected districts)

Notes:

• FAR. Not found in retrieved materials as a countywide standard; confirm for any project- or overlay-specific FAR.
• Multiple detached units on large lots may be allowed with a land use permit, subject to minimum land area per dwelling by district (e.g., R‑6 = 6,000 sf/unit, R‑10 = 10,000 sf/unit) (§ 84‑4.404(5) ).
• Airport approach overlays may impose lower effective heights than base districts (§ 86‑4.014 ).

Checklist

• Confirm the parcel is in the unincorporated areas and identify its base district and any overlays on the County zoning map (§ 82‑2.004 ).
• Verify base-district dimensional standards: minimum lot area/width/depth, setbacks, height, and any coverage limits (district‑specific §§ in Division 84).
• Screen for overlay constraints: HE‑C, airport height, hillside/open-space policies, etc. (§§ 84‑92.604; 86‑4.014; 82‑1.016 ).
• If planning ADUs, apply the state “safe harbor” (≥800 sf, 4‑ft side/rear) and County allowances; ensure local standards do not preclude state minimums (Gov. Code §§ 66321–66323; County residential chapters) .
• Check Contra Costa County Parking counts and placement, especially in R‑ districts (e.g., § 84‑4.1202) .
• Determine whether a development plan or site plan/elevations approval is explicitly required for your district (e.g., M‑ and N‑B districts, HE‑C) (§§ 84‑26.1802; 84‑50.1602; 84‑92.802) .
• If nonconforming or substandard lots are involved, review Contra Costa County Nonconforming Uses and § 82‑10.002(c) small‑lot provisions .
• For any needed relief, see Contra Costa County Variances and Exceptions.

Risks & Ambiguities

Plain-English Summary

If you’re building in the unincorporated areas, your lot’s district sets your minimum lot size, setbacks from the street and neighbors, and a typical max height of 35 ft. Larger-lot districts push yards wider; office/industrial districts carry deeper front or side yards, coverage caps, or both. Overlays—including airport height and Housing Element Combining (HE‑C)—can change the numbers, and state ADU law guarantees at least an 800‑sf ADU with 4‑ft side/rear setbacks even if your district would normally require more.

Source References

• Division 82, Countywide rules and definitions: §§ 82‑1.010, 82‑2.004, 82‑2.006, 82‑2.008, 82‑2.010, 82‑10.002, 82‑12.202 (cross‑ref) .
• R‑district dimensional standards: R‑6 §§ 84‑4.602–.1006, .802, .1202; R‑7 §§ 84‑6.602–.1006, .802; R‑10 §§ 84‑8.602–.1006, .802; R‑12 §§ 84‑10.602–.1006, .802; R‑15 §§ 84‑12.602–.1006, .802; R‑20 §§ 84‑14.602–.1006, .802; R‑40 §§ 84‑16.602–.1006, .802; R‑65 §§ 84‑18.602–.1006, .802; R‑100 §§ 84‑20.602–.1006, .802 .
• D‑1 two‑family: §§ 84‑22.602–.1006, .802, .1202 .
• Multi‑family M‑districts: M‑29 §§ 84‑26.1402, ‑26.1602, ‑26.1802; M‑12 § 84‑29.404; M‑9 § 84‑30.402; M‑6 § 84‑31.404 .
• Commercial/Office/Industrial: C §§ 84‑54.402–.1004; R‑B §§ 84‑52.602, .802, .1002, .1004; O‑1 §§ 84‑44.402, .602–.1002, .608, .802; L‑I §§ 84‑58.402–.1004, .602, .802; C‑M §§ 84‑56.602–.1004, .604, .802, .1202, .1602 .
• Agricultural/Forestry: A‑3 §§ 84‑40.802, ‑40.1002–.1006; A‑4 §§ 84‑42.602–.1206, ‑42.1002; F‑R §§ 84‑32.402, .602, .802, .1002–.1004 .
• Overlays: HE‑C §§ 84‑92.604, ‑92.802; Airport Height §§ 86‑4.012, ‑4.014 .
• State ADU law reference (HCD 2025 ADU Handbook excerpts): side/rear 4‑ft minimums; minimum 800 sf; height parameters; local standards may not preclude (§§ 66321–66323 Gov. Code) .
• For related process/criteria pages: Contra Costa County Land Use, Contra Costa County Design Review, Contra Costa County Overlay Districts, California Building Standards Code.

Retrieved passages

• Contra Costa County Zoning Code (§ II) High relevance show source text
• CBC § 66314 (§ 66314) High relevance show source text
• Contra Costa County Zoning Code (Article 84-10.10.) Medium relevance show source text
• Contra Costa County Zoning Code (Chapter 82-24.) Medium relevance show source text
• CBC § 4 (§ XI) Medium relevance show source text
• Contra Costa County Zoning Code (chapter the) Medium relevance show source text
• Contra Costa County Zoning Code (§ 3) Medium relevance show source text
• CFC § 66314 (§ 66314) Medium relevance show source text
• Contra Costa County Zoning Code (§ 5) High relevance show source text
• Contra Costa County Zoning Code (§ 1) High relevance show source text
• Contra Costa County Zoning Code (§ 8158) High relevance show source text
• Contra Costa County Zoning Code (§ VIII) High relevance show source text
• Contra Costa County Zoning Code (§ 8148.7) High relevance show source text
• Contra Costa County Zoning Code (§ 3) High relevance show source text
• Contra Costa County Zoning Code (§ II) High relevance show source text
• Contra Costa County Zoning Code (Article 84-56.6.) High relevance show source text
• Contra Costa County Zoning Code (Section 84-44.608) High relevance show source text
• Contra Costa County Zoning Code (§ 8145) Medium relevance show source text
• Contra Costa County Zoning Code (title 22) Medium relevance show source text
• Contra Costa County Zoning Code (§ 6) Medium relevance show source text
• Contra Costa County Zoning Code (§ IV) Medium relevance show source text
• Contra Costa County Zoning Code (Section 84-4.602) High relevance show source text
• Contra Costa County Zoning Code (Article 84-4.8.) High relevance show source text
• Contra Costa County Zoning Code (§ 8143) High relevance show source text
• Contra Costa County Zoning Code (§ 8148) High relevance show source text
• Contra Costa County Zoning Code (§ 8148) High relevance show source text
• Contra Costa County Zoning Code (Article 84-52.6.) Medium relevance show source text
• Contra Costa County Zoning Code (§ 8143) High relevance show source text
• Contra Costa County Zoning Code (§ 8149) High relevance show source text
• Contra Costa County Zoning Code (§ 8146) High relevance show source text

Cited sections

• Division 82, Countywide rules and definitions: §§ 82‑1.010, 82‑2.004, 82‑2.006, 82‑2.008, 82‑2.010, 82‑10.002, 82‑12.202 (cross‑ref) . (§ 82)
• R‑district dimensional standards: **R‑6** §§ 84‑4.602–.1006, .802, .1202; **R‑7** §§ 84‑6.602–.1006, .802; **R‑10** §§ 84‑8.602–.1006, .802; **R‑12** §§ 84‑10.602–.1006, .802; **R‑15** §§ 84‑12.602–.1006, .802; **R‑20** §§ 84‑14.602–.1006, .802; **R‑40** §§ 84‑16.602–.1006, .802; **R‑65** §§ 84‑18.602–.1006, .802; **R‑100** §§ 84‑20.602–.1006, .802 . (§ 84)
• D‑1 two‑family: §§ 84‑22.602–.1006, .802, .1202 . (§ 84)
• Multi‑family M‑districts: **M‑29** §§ 84‑26.1402, ‑26.1602, ‑26.1802; **M‑12** § 84‑29.404; **M‑9** § 84‑30.402; **M‑6** § 84‑31.404 . (§ 84)
• Commercial/Office/Industrial: **C** §§ 84‑54.402–.1004; **R‑B** §§ 84‑52.602, .802, .1002, .1004; **O‑1** §§ 84‑44.402, .602–.1002, .608, .802; **L‑I** §§ 84‑58.402–.1004, .602, .802; **C‑M** §§ 84‑56.602–.1004, .604, .802, .1202, .1602 . (§ 84)
• Agricultural/Forestry: **A‑3** §§ 84‑40.802, ‑40.1002–.1006; **A‑4** §§ 84‑42.602–.1206, ‑42.1002; **F‑R** §§ 84‑32.402, .602, .802, .1002–.1004 . (§ 84)
• Overlays: **HE‑C** §§ 84‑92.604, ‑92.802; Airport Height §§ 86‑4.012, ‑4.014 . (§ 84)
• State ADU law reference (HCD 2025 ADU Handbook excerpts): side/rear 4‑ft minimums; minimum 800 sf; height parameters; local standards may not preclude (§§ 66321–66323 Gov. Code) . (§ 66321)
• For related process/criteria pages: Contra Costa County Land Use, Contra Costa County Design Review, Contra Costa County Overlay Districts, California Building Standards Code.
• ContraCostaCounty_ZoningCode.md
• 2025 California ADU handbook.md
• 2022 PGE Greenbook.md

• Official Contra Costa County code library