Alameda County spans the East Bay’s waterfront cities, hillside neighborhoods, suburban communities, and inland valleys. Explore ADU information for Oakland and the county’s many distinctive residential areas.
Incorporated cities inside Alameda County adopt their own ADU standards, so a property inside city limits follows that city's rules. County standards apply to the unincorporated areas.
Rules are grouped by topic. Open a topic for the answers, the conditions on them, and the official source each one came from. Each rule names the authority that set it: Statewide standard and Alameda County standard.
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64 rules
What can I build?
The kinds of accessory dwelling unit this jurisdiction recognises.11 rules
Detached ADU allowed
Allowed
Detached ADUs are authorized on the same lot as a proposed or existing primary dwelling.
Set by: Statewide standard
In force from: Effective
Explanation
Whether a detached, newly constructed ADU is permitted.
Part of Statewide, published by California.
Source
California Government Code, Title 7, Division 1, Chapter 13, § Gov. Code § 66314(d)(3)
Source document
California Government Code, Title 7, Division 1, Chapter 13
JADUs are locally limited to R-1 single-family properties.
Set by: Alameda County standard
Note: Conditions apply
Allowed
JADUs are authorized on qualifying single-family residential lots with a proposed or existing single-family residence.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Where a topic is recorded at more than one level, both entries are shown with the authority that set them. Which one governs a particular property is a question for the responsible planning agency.
Explanation — Alameda County standard
Whether a junior ADU is permitted.
When this applies
Applies when all of the following are true:
Property primary structure type is Single family
Property zoning is R-1
Part of Alameda Local Rules, published by Alameda County.
Explanation — Statewide standard
Whether a junior ADU is permitted.
When this applies
Applies when all of the following are true:
Property primary structure type is Single family
Part of Statewide, published by California.
Source — Alameda County standard
Accessory Dwelling Units ADU Handout, June 2024, § Question 5
Multifamily sites may have up to two detached ADUs.
Set by: Alameda County standard
Note: Conditions apply
Up to 2 count
A single-family site may have one new-construction ADU and one conversion ADU, subject to attachment limits.
Set by: Alameda County standard
Note: Conditions apply
Up to 2 count
A lot with a proposed multifamily dwelling may have up to two detached ADUs.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Up to 8 count
An existing multifamily lot may have up to eight detached ADUs, but no more than its existing dwelling-unit count.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Up to 1 count
One detached new-construction ADU is ministerially allowed on a qualifying single-family lot.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Where a topic is recorded at more than one level, both entries are shown with the authority that set them. Which one governs a particular property is a question for the responsible planning agency.
Explanation — Alameda County standard
Greatest number of detached ADUs permitted on the property.
When this applies
Applies when all of the following are true:
Property primary structure type is Multifamily
Part of Alameda Local Rules, published by Alameda County.
Explanation — Alameda County standard
Greatest number of detached ADUs permitted on the property.
When this applies
Applies when all of the following are true:
Property primary structure type is Single family
Part of Alameda Local Rules, published by Alameda County.
Explanation — Statewide standard
Greatest number of detached ADUs permitted on the property.
When this applies
Applies when all of the following are true:
Property primary structure type is Multifamily
Property has existing primary dwelling is no
Part of Statewide, published by California.
Explanation — Statewide standard
Greatest number of detached ADUs permitted on the property.
When this applies
Applies when all of the following are true:
Property primary structure type is Multifamily
Property has existing primary dwelling is yes
Part of Statewide, published by California.
Explanation — Statewide standard
Greatest number of detached ADUs permitted on the property.
When this applies
Applies when all of the following are true:
Property primary structure type is Single family
Part of Statewide, published by California.
Source — Alameda County standard
Alameda County Board of Supervisors ADU/JADU Ordinance, § Section 17.55.050(2)
Source document
Alameda County Board of Supervisors ADU/JADU Ordinance
An ADU is a residential use consistent with the lot's existing general-plan and zoning designations where the lot allows single-family or multifamily residential use.
Explanation
Whether the zoning district permits ADUs.
Part of Statewide, published by California.
Source
California Government Code, Title 7, Division 1, Chapter 13, § Gov. Code § 66314(c)
Source document
California Government Code, Title 7, Division 1, Chapter 13
New-construction ADUs with more than one bedroom are limited to 1,200 square feet.
Set by: Alameda County standard
Note: Conditions apply
Up to 850 sqft
New-construction ADUs with one bedroom or less are limited to 850 square feet.
Set by: Alameda County standard
Note: Conditions apply
Up to 1,200 sqft
A detached ADU may not exceed 1,200 square feet under the statewide baseline.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Where a topic is recorded at more than one level, both entries are shown with the authority that set them. Which one governs a particular property is a question for the responsible planning agency.
Explanation — Alameda County standard
Greatest permitted floor area of the ADU.
When this applies
Applies when all of the following are true:
Project bedrooms is more than 1
Project construction type is one of Detached new, Attached new, Addition
Part of Alameda Local Rules, published by Alameda County.
Explanation — Alameda County standard
Greatest permitted floor area of the ADU.
When this applies
Applies when all of the following are true:
Project bedrooms is at most 1
Project construction type is one of Detached new, Attached new, Addition
Part of Alameda Local Rules, published by Alameda County.
Explanation — Statewide standard
Greatest permitted floor area of the ADU.
When this applies
Applies when all of the following are true:
Project unit type is Detached adu
Part of Statewide, published by California.
Source — Alameda County standard
Accessory Dwelling Units ADU Handout, June 2024, § Question 8, Attached ADU standards
A single-family attached addition over 800 square feet may not exceed half of the primary dwelling’s living area.
Set by: Alameda County standard
Note: Conditions apply
Up to 50 percent
An attached ADU on a lot with an existing primary dwelling may not exceed half of the primary dwelling's floor area.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Where a topic is recorded at more than one level, both entries are shown with the authority that set them. Which one governs a particular property is a question for the responsible planning agency.
Explanation — Alameda County standard
Greatest permitted ADU floor area expressed as a percentage of the primary dwelling.
When this applies
Applies when all of the following are true:
Project unit type is Attached adu
Project construction type is one of Attached new, Addition
Project proposed size sqft is more than 800
Property primary structure type is Single family
Part of Alameda Local Rules, published by Alameda County.
Explanation — Statewide standard
Greatest permitted ADU floor area expressed as a percentage of the primary dwelling.
When this applies
Applies when all of the following are true:
Project unit type is Attached adu
Property has existing primary dwelling is yes
Part of Statewide, published by California.
Source — Alameda County standard
Accessory Dwelling Units ADU Handout, June 2024, § Question 8, Attached ADU standards
When parking has to be provided, and when it is excused.9 rules
Parking spaces required
Up to 1 spaces
New-construction attached or detached ADUs require no more than one space, based on the lesser of units or bedrooms.
Set by: Alameda County standard
Note: Conditions apply
0 spaces
No additional parking may be required for a JADU.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Up to 1 spaces
ADU parking may not exceed one space per ADU or per bedroom, whichever is less; JADUs may not require additional parking.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Where a topic is recorded at more than one level, both entries are shown with the authority that set them. Which one governs a particular property is a question for the responsible planning agency.
Explanation — Alameda County standard
Off-street parking spaces required for the ADU.
When this applies
Applies when all of the following are true:
Project construction type is one of Detached new, Attached new, Addition
Part of Alameda Local Rules, published by Alameda County.
Explanation — Statewide standard
Off-street parking spaces required for the ADU.
When this applies
Applies when all of the following are true:
Application type is Jadu
Part of Statewide, published by California.
Explanation — Statewide standard
Off-street parking spaces required for the ADU.
When this applies
Applies when all of the following are true:
Application type is one of Adu, Adu and jadu
Part of Statewide, published by California.
Source — Alameda County standard
Accessory Dwelling Units ADU Handout, June 2024, § Question 6
Connections, meters and the charges that come with them.8 rules
Separate utility meter required
Not required
For qualifying conversion ADUs and JADUs, a new or separate direct utility connection may not be required except with a new single-family dwelling or separate conveyance.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Explanation
Whether the ADU must have its own utility meter.
When this applies
Applies when all of the following are true:
Project construction type is one of Interior conversion, Accessory structure conversion, Garage conversion
Part of Statewide, published by California.
Source
California Government Code, Title 7, Division 1, Chapter 13, § Gov. Code § 66311.5(d)
Source document
California Government Code, Title 7, Division 1, Chapter 13
Projects involving a new septic system require an Environmental Health permit.
Set by: Alameda County standard
Note: Conditions apply
Required
Where a private sewage-disposal system is used, local-health-officer approval may be required.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Where a topic is recorded at more than one level, both entries are shown with the authority that set them. Which one governs a particular property is a question for the responsible planning agency.
Explanation — Alameda County standard
Whether septic system review or approval is required.
When this applies
Applies when all of the following are true:
Property sewer type is Septic
Part of Alameda Local Rules, published by Alameda County.
Explanation — Statewide standard
Whether septic system review or approval is required.
When this applies
Applies when all of the following are true:
Property sewer type is Septic
Part of Statewide, published by California.
Source — Alameda County standard
Accessory Dwelling Units ADU Handout, June 2024, § Question 11
A completed ADU or JADU application on a lot with an existing qualifying dwelling must be approved or denied within 60 days; applicant-requested delay tolls the period.
In force from: Effective
Note: Conditions apply
Explanation
Longest period the agency may take to approve or deny a completed application. Frequently scoped to lots with an existing dwelling; that condition belongs in the claim's applicability, not in this description.
When this applies
Applies when all of the following are true:
Property has existing primary dwelling is yes
Part of Statewide, published by California.
Source
California Government Code, Title 7, Division 1, Chapter 13, § Gov. Code §§ 66317(a)(3), 66335(a)(3)
Source document
California Government Code, Title 7, Division 1, Chapter 13
Maximum period to act on a coastal development permit
Up to 60 days
A completed coastal development permit application for an ADU must be approved or denied within 60 days, subject to the concurrent-primary-dwelling exception.
In force from: Effective
Note: Conditions apply
Explanation
Longest period the agency may take to act on a coastal development permit application. Separate from the underlying ADU application timeline.
When this applies
Applies when all of the following are true:
Property overlays includes Coastal overlay
Part of Statewide, published by California.
Source
California Government Code, Title 7, Division 1, Chapter 13, § Gov. Code § 66329(a)
Source document
California Government Code, Title 7, Division 1, Chapter 13
For a detached garage replaced by an ADU, written notice or placarding for demolition cannot be required outside an architecturally and historically significant historic district.
In force from: Effective
Note: Conditions apply
Explanation
Whether a demolition permit review or delay applies to the project.
When this applies
Applies when all of the following are true:
Property overlays does not include Historic district
Part of Statewide, published by California.
Source
California Government Code, Title 7, Division 1, Chapter 13, § Gov. Code § 66314(f)
Source document
California Government Code, Title 7, Division 1, Chapter 13
Who may live in an ADU, and how it may be rented or sold.6 rules
Minimum rental term
At least 30 days
ADUs and JADUs may not be rented for fewer than 30 days.
Set by: Alameda County standard
At least 31 days
ADU and JADU rentals must be for terms longer than 30 days.
Set by: Statewide standard
In force from: Effective
Where a topic is recorded at more than one level, both entries are shown with the authority that set them. Which one governs a particular property is a question for the responsible planning agency.
Explanation — Alameda County standard
Shortest rental term permitted for the ADU.
Part of Alameda Local Rules, published by Alameda County.
Explanation — Statewide standard
Shortest rental term permitted for the ADU.
Part of Statewide, published by California.
Source — Alameda County standard
Accessory Dwelling Units ADU Handout, June 2024, § Question 7(a)
Source document
Accessory Dwelling Units ADU Handout, June 2024
Publisher
Alameda County
Document type
Ordinance
Source type
Official guidance
Section
Question 7(a)
Source checked
August 23, 2026
Excerpt
may not be rented for a period of fewer than 30 days
An ADU or JADU generally may not be sold separately from the primary residence, subject to a statutory separate-conveyance exception not captured by this broad rule.
Set by: Statewide standard
In force from: Effective
Note: Conditions apply
Explanation
Whether the ADU may be sold separately from the primary dwelling.
When this applies
Applies when all of the following are true:
Project separate sale intended is yes
Part of Statewide, published by California.
Source
California Government Code, Title 7, Division 1, Chapter 13, § Gov. Code § 66314(d)(1)
Source document
California Government Code, Title 7, Division 1, Chapter 13
ADUDesk summarises recorded rules for informational purposes and may not include every requirement. Confirm current requirements with the responsible planning agency before making design, purchase, or permit decisions.
About this information
Dates, versions and how rules are recorded
Rules are recorded from official sources and each one links to the document it came from. A source check confirms the document was retrieved and read; it is not a legal review, and the record may not cover every requirement that applies to a property or project.
Report as of
The date the rules on this page were resolved for.
Jurisdiction record reviewed
Not recordedWhen this jurisdiction's record was last checked. Not a legal review.
Statewide
Published by California
Rule-set effective from
Published
Statewide rules reviewed
A staff check of this rule set against its sources.
What changed in this version: Initial
Alameda Local Rules
Published by Alameda County
Rule-set effective from
Published
Local rules reviewed
A staff check of this rule set against its sources.
What changed in this version: Created from V2 research draft #2 (run #18).
