Local zoning · Alameda County

Alameda County — Zoning

Q: What can I build on an R‑1 lot in unincorporated Alameda County?

An R‑1 lot generally allows one one‑family dwelling and limited horticultural uses; in Castro Valley some day‑care uses are explicitly permitted. Conditional uses (community facilities, certain parking, nurseries, larger care facilities) require approval by the Board of Zoning Adjustments (§ 17.08.030; § 17.08.040) .

Q: What if my project is partly commercial and partly residential?

Mixed-use sites are explicitly recognized in M‑U and other districts; when residential and commercial coexist the residential portion must meet the residential standards and the commercial portion must meet the commercial standards of the zoning title (see § 17.13.010 and Sunol “SD” mixed rules) — verify both district chapters and any applicable site development review requirements file.

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

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Last reviewed: July 3, 2026

Overview

Zoning in Alameda County applies only to the county's unincorporated areas and is administered through Title 17 of the Alameda County Ordinance (commonly called the zoning ordinance). The ordinance establishes an official zoning map, base districts (residential, commercial, industrial, agricultural, etc.), and a number of combining/overlay districts used to calibrate density and permitstreamlining. Confirm district boundaries on the official zoning map before planning a project — the map and its rules are the legal starting point for any land-use analysis (§ 17.02.090; § 17.02.100) .

For background on how zoning fits with other review topics, see Alameda County’s general Land Use overview and the county Development Standards guidance. Practical steps for applicants (parking calculations, when design review applies, and overlay rules) are summarized below and linked to the county menu pages as they arise.

How the ordinance is structured (short)

The list of established districts is in § 17.02.060 (the ordinance enumerates A, R-1, R-2, R-S, M-U, R-3, R-4, SD, PD, HP, various combining districts such as B, D, DV, L, X, S, F, housing-element HE overlays, numerous commercial and industrial districts, and a Castro Valley (CV) chapter) .
The official zoning map shows district boundaries for all lands in unincorporated Alameda County and is maintained by the Planning Commission (§ 17.02.090 — § 17.02.100) .
Combining districts (density, sign control, housing-element overlays) modify or add to the base-district standards; where a conflict exists the overlay language can govern (§ 17.31.040) .

For project-level standards see the county pages on development standards, parking, and design review.

District-by-district (selected, ordinance-grounded)

Note: each district subsection below summarizes the ordinance language for the unincorporated areas. Where the code text retrieved does not include specific numeric dimensional controls for a district, I note that as "Not found in retrieved materials" and advise verification with the Planning Department.

A (Agricultural)

Purpose: The A district is intended for agricultural uses and to protect farming/open-space patterns; the district is established at Chapter 17.06 (district list) .
Typical permitted uses: The ordinance enumerates the A district but specific permitted-use list and numeric standards for A were not included in the retrieved snippets. Verify permitted uses in Chapter 17.06. Not found in retrieved materials to quote exact uses or setbacks .
Key dimensional standards: Not found in retrieved materials — verify with Chapter 17.06 and the zoning map.
Where it applies: Parcels shown as A on the official zoning map (§ 17.02.090) .

R-1 (Single-family residence)

Purpose: R-1 protects one-family neighborhoods and allows limited compatible community uses (§ 17.08.010) .
Typical permitted uses: One one-family dwelling and limited horticultural uses; small- and large-family day care are specifically allowed in Castro Valley areas (§ 17.08.030) .
Conditional uses: Community facilities, parking to serve abutting lots, plant nurseries, medical/residential care (7+ persons) subject to BZA approvals (§ 17.08.040) .
Key dimensional standards: The retrieved materials do not provide a full table of setbacks/height for R‑1 in the excerpts; the code does reference some side-yard rules (e.g., side yard may be none except five feet where abutting residential) but the specific section number for standard setbacks was not retrieved in full. Verify numeric setbacks and height limits in Chapter 17.08 and cross-check the county Development Standards page (§ 17.08.020—§ 17.08.040 referenced) .
Where it applies: Parcels mapped R-1 in unincorporated Alameda County (§ 17.02.060; § 17.08.020) .

R-2 (Two-family residence)

Purpose & uses: The ordinance lists R-2 districts at Chapter 17.10; the retrieved file list includes the district designation but not the full text of permitted uses in the excerpts. Verify Chapter 17.10 for uses and standards (§ 17.02.060) .
Key dimensional standards: Not found in retrieved materials — verify with Chapter 17.10.

R-S (Suburban residence)

Purpose: R-S supports suburban residential patterns and is often combined with D or DV districts to vary intensity (§ 17.12 & 17.24—17.25) .
Typical uses: Residential uses consistent with suburban density; required open-space standards are referenced (§ 17.12.120 lists usable open space requirements) .
Key dimensional standards: Chapter 17.24 (D combining districts) provides dwelling-unit-area calculations (e.g., D-35 = 3,500 sq ft per unit, D-25 = 2,500, D-20 = 2,000, D-15 = 1,500) — see § 17.24.040 and Table 17.24.040 .

R-3 (Four-family)

Purpose: R-3 allows limited multiple dwellings (up to four units) (§ 17.14.010) .
Typical permitted uses: One- to four-family dwellings, limited medical/residential care up to six persons, transitional/supportive housing up to six persons; day care in Castro Valley (§ 17.14.020) .
Key dimensional standards: The ordinance references design standards and the county “Residential Design Standards and Guidelines” for R‑3 in certain planning areas (§ 17.14.015); numeric setbacks/height not fully reproduced in the retrieved snippets — verify Chapter 17.14 and the design guidelines .

R-4 (Multiple residence / high density)

Purpose & uses: R-4 supports higher-density residential development; Chapter 17.16 is the base for standards and the HE overlay references R‑4 types for design guidelines (§ 17.31.240; § 17.31.130) .
Key dimensional standards: HE overlay ties minimum/maximum densities for some districts; see HE overlay subsections for numeric density ranges where applicable .

M-U (Mixed Use residential/commercial)

Purpose: M‑U regulates combined residential and commercial on the same building site to maintain neighborhood compatibility (§ 17.13.010) .
Typical permitted uses: Mixed residential/commercial per Chapter 17.13; site development review is required for disposition of buildings and parking/ circulation (§ 17.13.020) .
Key dimensional standards: Max height is explicitly stated: 35 feet for structures unless excepted (§ 17.13.080) .
Where it applies: Parcels mapped M‑U in unincorporated areas (§ 17.02.060) .

C-N, C-1, C-2 (Commercial)

Purpose & uses: These are the county's neighborhood, retail and general commercial districts (Chapters 17.36, 17.38, 17.40 referenced in the district list) — the enumeration is in § 17.02.060 .
Permitted uses & dimensional standards: Specific use lists and standards live in the chapters listed above; the HE overlay (Chapter 17.31) can modify allowed residential/mixed‑use outcomes on certain parcels (§ 17.31.140) .
Where it applies: Parcels mapped C‑N/C‑1/C‑2 on the official zoning map (§ 17.02.090) .

M-1, M-2, M-P (Industrial / Industrial Park)

Purpose & uses: Light and heavy industrial districts and industrial park designations are enumerated (Chapters 17.44, 17.46, 17.42) — use details are in those chapters (§ 17.02.060) .
Key dimensional standards: Not found in the retrieved snippets — verify Chapters 17.42–17.46 for setbacks, buffering, and conditional uses.

PD (Planned Development)

Purpose: PD districts promote integrated, flexible development that conforms to General Plan policies and preserves open space and amenities (§ 17.18.010) .
Typical process & standards: A change to PD requires the procedures in Chapter 17.54, submission of preliminary land use and development plans (professional certifications required), public hearings, and a planning commission evaluation (§ 17.18.020—§ 17.18.070) .
Where it applies: Only where the county rezones to PD; PD regulations apply once the zoning change is adopted (§ 17.18.020) .

HP (Historical preservation)

Purpose: HP is a historic-preservation combining district (Chapter 17.20 listed); it modifies the base district to protect identified historic resources (§ 17.02.060) .
Key standards: Not fully reproduced in the retrieved snippets — verify Chapter 17.20 for permitted work, design review triggers, and demolition controls.

Combining districts: B, D, DV, S, L, X

Purpose: Combining districts adjust site-area/density (D and DV), add sign control (S), agricultural-use combining (L), air pollution controls (X), and other site-specific rules (§ 17.24; § 17.25; § 17.30; § 17.26; § 17.28) .
Example: The D table sets required number of square feet per dwelling unit (e.g., D‑35 = 3,500 sq ft/unit), which is used to calculate maximum units for a given lot (§ 17.24.040; Table 17.24.040) .
Where to verify: See the combining-district chapters for specifics.

Housing Element overlay (HE combining district)

Purpose: The HE overlay is a housing-element zoning overlay that is combined with base districts to implement the 2023–2031 housing element, provide permit streamlining, and set objective standards and densities (§ 17.31.010—§ 17.31.050) .
Key rules: Parcels within the HE map are subject to the HE provisions; the overlay can (1) allow residential uses as primary uses regardless of base district if specified, (2) provide ministerial (by-right) approvals for qualifying affordable projects, and (3) fix minimum/maximum densities on specific HE sites (e.g., RSL‑17‑HE, RMF‑29‑HE, HDR‑86‑HE) (§ 17.31.030—§ 17.31.050; § 17.31.200—§ 17.31.260) .
Parking: The HE chapter caps parking requirements for HE projects and sets maximum per-unit parking by unit type (studio = 1, 1BR = 1.5, 2+BR = 2, with aggregate caps) (§ 17.31.090) — see county parking for cross-reference .
Sunset: The HE overlay will sunset upon adoption of the next (7th) cycle housing element (§ 17.31.110) .

RSL (Residential Small Lot) — example of a district with local design standards

Purpose: RSL supports small‑lot infill (duplexes, small detached, townhouses) in Castro Valley and elsewhere (§ 17.51.020) .
Permitted uses & conditional uses: One- to multiple-dwelling types, limited care/transitional housing, day care; conditional uses include community facilities and parking where meeting residential parking requirements (§ 17.51.020(C–D)) .
Design standards: Projects in RSL in Castro Valley are subject to the county "Residential Design Standards and Guidelines for the Unincorporated Communities of West Alameda County" (§ 17.51.020(B)) — consult the design guidelines and the Design Review page .

Quick reference table — selected decision-relevant standards and code citations

Topic / District	Quick rule or common permit trigger	Code Reference
Official zoning map (unincorp.)	Zoning map shows district classification; planning commission keeps official copy	§ 17.02.090; § 17.02.100
District list (which zones exist)	Base and combining districts enumerated (A, R‑1, R‑2, R‑S, M‑U, R‑3, R‑4, PD, HP, HE overlays, C‑N, C‑1, C‑2, M‑1, M‑2, etc.)	§ 17.02.060
R‑1 permitted uses	One single‑family dwelling; limited agriculture; day care in Castro Valley	§ 17.08.030
R‑3 permitted uses	Up to four dwelling units; limited care/transitional housing rules	§ 17.14.020
PD (Planned Development)	Requires rezoning, preliminary plan, professional certifications, PC review	§ 17.18.010–§ 17.18.070 file
Housing Element overlay (HE)	Overlay defines parcel list, dims/densities and can provide by‑right approvals for qualifying affordable projects; caps HE parking	§ 17.31.010—§ 17.31.050; § 17.31.090 file
Combining D districts	Square‑feet per dwelling unit formula (D‑35, D‑25, D‑20, etc.)	§ 17.24.040 (Table 17.24.040)
Site development review triggers	Many districts require site development review for larger projects (e.g., >10 units, >1,000 sq ft non‑res.)	See district chapters and Chapter 17.54; examples in § 17.31.200—210

Practical guidance & interpretation (plain-English synthesis)

Start at the official zoning map: confirm the zoning designation for YOUR parcel (the map is the legal source of district boundaries — § 17.02.090; disputes over boundaries are decided by the Planning Commission under § 17.02.110) file.
Match uses to the base district's permitted/conditional lists. If your parcel is inside an HE overlay or other combining district, read the overlay chapter first because the overlay can change permit procedures, allowed residential uses, and density limits (§ 17.31.040) .
If you plan housing on an HE parcel, note the parking caps and ministerial/streamlined pathways for qualifying affordable projects — see § 17.31.090 and the HE review table (Table 1) for process/density mapping file.
Design rules and site‑specific standards: many residential districts within Castro Valley, San Lorenzo, Ashland, Cherryland and Fairview refer applicants to the county "Residential Design Standards and Guidelines for the Unincorporated Communities of West Alameda County" — use those design guidelines when numeric standards are not spelled out in the zoning chapter (§ 17.08.015; § 17.18.015; § 17.14.015) file.
For dimensional questions (setbacks, height, lot coverage) consult the specific district chapter and the county Development Standards. For construction code compliance, coordinate with the California Building Standards Code (Title 24) — zoning decides use and siting; Title 24 decides construction and life-safety.

Checklist — what an applicant must satisfy (unincorporated Alameda County)

Confirm the parcel's official zoning designation on the county zoning map and any combining/overlay districts (§ 17.02.090; § 17.31.020) file.
Verify the use is listed as permitted in the base district or permitted via overlay; if not, evaluate conditional use/rezoning routes (§ 17.02.060; district chapters) .
Check whether the parcel is in an HE overlay and whether the project qualifies for by‑right or ministerial processing (§ 17.31.040—§ 17.31.050) .
Confirm dimensional standards (setbacks, height, lot coverage) in the specific district chapter or design standards referenced therein; consult county Development Standards and applicable design guidelines (§ 17.08.015; § 17.51.020) file.
Calculate parking using county limits and HE special caps where applicable; consult the county parking guidance and § 17.31.090 for HE parcels .
Determine whether Site Development Review, Design Review, or Board of Zoning Adjustments approval is required (e.g., >10 units, >1,000 sq ft non‑res., or specific conditional uses) and prepare the required application materials (§ 17.31.200—§ 17.31.240; Chapter 17.54) .
Where applicable, follow the "Residential Design Standards and Guidelines for the Unincorporated Communities of West Alameda County" for Castro Valley and other planning areas (§ 17.08.015; § 17.51.020) file.
If building, confirm compliance with the California Building Standards Code and applicable permitting channels; zoning approval does not replace building permits.

Risks & Ambiguities

Issue	Why it matters	What to verify
District boundary uncertainty	Boundaries on the zoning map can be ambiguous at lot lines; approvals depend on the mapped district	Verify the official zoning map and, if ambiguous, request Planning Commission determination under § 17.02.110
Overlay vs base conflict (HE overlay)	The HE overlay can supersede base rules (permit streamlining, density) and change whether a use is allowed	Confirm whether the parcel is in the HE overlay and which overlay provisions apply (see § 17.31.040)
Design‑standards cross‑references (Castro Valley, etc.)	Some districts defer numeric standards to separate design guidelines; lacking those can stall plan completeness	Check the specific district note that references the "Residential Design Standards and Guidelines" (e.g., § 17.08.015, § 17.51.020) file
Parking caps under HE overlay	HE parking caps may differ from base district; underestimating required parking triggers re‑submittal	Use § 17.31.090 for HE projects; confirm transit proximity adjustments and state law exceptions
Missing numeric setbacks/heights in retrieved snippets	Many district chapters have numeric controls not present in the excerpts; relying on summaries risks error	Consult the full district chapter in Title 17 and county Development Standards; verify with Planning staff
Sunset of HE overlay	HE provisions are time-limited pending the next housing element; project timing matters for eligibility	Verify current status: § 17.31.110 notes sunset on adoption of the 7th cycle housing element

Plain-English Summary

If your property is in unincorporated Alameda County, first check the official zoning map to see which district and any overlays (like the housing element overlay) apply; then read that district’s permitted-use list and the district chapter in Title 17 for dimensional standards, conditional-use triggers, and site‑development review requirements. Overlays (especially the HE overlay) can change allowed uses, density and parking rules — always confirm the map and applicable § text before designing a project (§ 17.02.090; § 17.31.040) file.

Source References

§ 17.02.060 — Districts enumerated (list of base and combining districts) .
§ 17.02.090 — Zoning map; classification of lands in unincorporated Alameda County .
§ 17.02.100 — Planning Commission maintains the official zoning map .
§ 17.02.110 — Procedure when district boundary uncertainty exists .
Chapter 17.08 (R‑1) — Intent, map designations, permitted and conditional uses (§ 17.08.010—§ 17.08.040) file.
Chapter 17.13 (M‑U) — Mixed‑use district intent and standards (§ 17.13.010—§ 17.13.090) file.
Chapter 17.14 (R‑3) — Four‑family district permitted uses and conditions (§ 17.14.010—§ 17.14.020) .
Chapter 17.18 (PD) — Planned Development intent and rezoning procedures (§ 17.18.010—§ 17.18.070) file.
Chapter 17.24 (D combining districts) — Dwelling units per required area, Table 17.24.040 (§ 17.24.040) .
Chapter 17.25 (DV combining districts) — Density variable district intent (§ 17.25.010—§ 17.25.040) .
Chapter 17.31 (Housing Element overlay combining district HE) — Intent, map, general provisions, review procedures, parking caps, and district‑specific densities (§ 17.31.010—§ 17.31.110; § 17.31.140—§ 17.31.260) file.
Chapter 17.51 (RSL & Castro Valley-specific standards) — Residential small lot district rules and design‑guideline references (§ 17.51.020) .
For related county topics referenced in this page: Alameda County zoning & planning overview, Alameda County Land Use, Alameda County Development Standards, Alameda County Parking, Alameda County Design Review, Alameda County Overlay Districts, Alameda County Nonconforming Uses, Alameda County Variances and Exceptions, California Building Standards Code, California ADU law.

Sources

Retrieved passages

Alameda County Zoning Code (Section 17.02.060) High relevance
Alameda County Zoning Code (§ 5) High relevance
Alameda County Zoning Code (Chapter 17.32) High relevance
Alameda County Zoning Code (§ 8-26.0) High relevance
Alameda County Zoning Code (§ 1) High relevance
Alameda County Zoning Code (Section 17.31.050) High relevance
Alameda County Zoning Code (Section 17.52.090.) High relevance
Alameda County Zoning Code (§ 1) High relevance

Cited sections

Official Alameda County code library

Frequently asked questions

What can I build on an R‑1 lot in unincorporated Alameda County?

An R‑1 lot generally allows one one‑family dwelling and limited horticultural uses; in Castro Valley some day‑care uses are explicitly permitted. Conditional uses (community facilities, certain parking, nurseries, larger care facilities) require approval by the Board of Zoning Adjustments (§ 17.08.030; § 17.08.040) .

How do I find the zoning for my unincorporated Alameda County parcel?

Use the county’s official zoning map — the ordinance requires the map show district classifications for all unincorporated lands and the Planning Commission to maintain the official copy (§ 17.02.090; § 17.02.100) . If a boundary is unclear, the Planning Commission can determine the location under § 17.02.110.

What is the Housing Element (HE) overlay and how does it affect my project?

The HE overlay is a combining district to implement the county’s housing element; it identifies parcels for streamlined housing approvals, sets site‑specific densities, and can provide by‑right approval for qualifying affordable projects. Where HE provisions conflict with base district rules, the HE governs (§ 17.31.010—§ 17.31.040) .

Do HE overlay parcels have different parking rules?

Yes. HE overlay projects have capped parking requirements and special reductions for transit-proximate sites; the HE chapter provides per‑unit maximums (studio = 1, 1BR = 1.5, 2+BR = 2, and an overall cap in some cases) — see § 17.31.090 and the county parking guidance .

When is Site Development Review or Design Review required?

Several districts require Site Development Review (SDR) for larger projects or significant remodels (examples in HE districts: construction of >10 units, remodels over 50% exterior volume, or >1,000 sq ft of non‑residential floor area triggers SDR). Many districts in the Castro Valley Urbanized Area also reference the Residential Design Standards and Guidelines, which can trigger design or site review (§ 17.31.200—§ 17.31.210; § 17.08.015) file.

Can the county change my parcel’s zoning designation?

Yes — district boundaries and classifications can be changed by Board of Supervisors action and, when changed, the zoning map is amended and certified by the Planning Director (see the map amendment rule § 17.02.120) .

Where are density rules like “D‑25” or “DV” explained?

The combining D districts define required square footage per dwelling unit (Table 17.24.040 lists D‑35 = 3,500 sq ft/unit, D‑25 = 2,500, etc.) and DV districts allow density variations tied to R‑S districts; see § 17.24.040 and § 17.25.010 for the combining district framework .

Does the zoning ordinance tell me how to comply with building codes or ADU law?

No. Zoning governs uses, density and siting. For construction and code compliance consult the California Building Standards Code and for ADU-specific state rules consult the California ADU law. Zoning chapters may note where ADUs are permitted by district but the construction/code checklist is separate — verify both sources.

What if my project is partly commercial and partly residential?

Mixed-use sites are explicitly recognized in M‑U and other districts; when residential and commercial coexist the residential portion must meet the residential standards and the commercial portion must meet the commercial standards of the zoning title (see § 17.13.010 and Sunol “SD” mixed rules) — verify both district chapters and any applicable site development review requirements file.

Who decides boundary disputes or appeals of Planning Commission actions?

The ordinance gives the Planning Commission authority to determine boundary locations under § 17.02.110, and many planning determinations are appealable to the Board of Supervisors under the procedures in Chapter 17.54 (appeal and hearing rules). Verify the exact appeal path in Chapter 17.54 for your case. Not all Chapter 17.54 excerpts were in the retrieved materials; verify with Planning staff for parcel‑specific appeal procedures. Not found in retrieved materials for full Chapter 17.54 text.

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