California ADU laws
The rules come from Cal. Gov. Code §§ 66310-66342. They cover approval deadlines, minimum sizes cities must allow, heights, setbacks and parking.
On this page
California sets statewide rules for accessory dwelling units that every city and county must follow. Local governments can add details, but not below these limits. Each rule below is quoted from the statute.
California ADU rules, in the statute's words
Cal. Gov. Code §§ 66310-66342 · in effect 1
- Ministerial, no hearing.
A permit application for an accessory dwelling unit shall be considered and approved ministerially without discretionary review or a hearing, notwithstanding Section 65901 or 65906 or any local ordinance regulating the issuance of variances or special use permits.
1 - 15 business days.
A permitting agency shall determine whether an application to create or serve an accessory dwelling unit is complete and provide written notice of this determination to the applicant not later than 15 business days after the permitting agency received the application.
1 - 60 days.
The permitting agency shall either approve or deny the application to create or serve an accessory dwelling unit within 60 days from the date the permitting agency receives a completed application if there is an existing single-family or multifamily dwelling on the lot.
1 - Deemed approved after 60 days.
If the local agency has not approved or denied the completed application within 60 days, the application shall be deemed approved.
1 - 1,200 square feet.
The total floor area for a detached accessory dwelling unit shall not exceed 1,200 square feet.
1 - 50%.
If there is an existing primary dwelling, the total floor area of an attached accessory dwelling unit shall not exceed 50 percent of the existing primary dwelling.
1 - 800 square feet.
Any requirement for a zoning clearance or separate zoning review or any other minimum or maximum size for an accessory dwelling unit, size based upon a percentage of the proposed or existing primary dwelling, or limits on lot coverage, floor area ratio, open space, front setbacks, and minimum lot size, for either attached or detached dwellings that does not permit an accessory dwelling unit with at least 800 square feet of interior livable space and with four-foot side and rear yard setbacks to be constructed in compliance with all other local development standards.
1 - 850 square feet.
Eight hundred fifty square feet of interior livable space.
1 - 1,000 square feet.
One thousand square feet of interior livable space for an accessory dwelling unit that provides more than one bedroom.
1 - 16 feet.
A height of 16 feet for a detached accessory dwelling unit on a lot with an existing or proposed single family or multifamily dwelling unit.
1 - 18 feet.
A height of 18 feet for a detached accessory dwelling unit on a lot with an existing or proposed single family or multifamily dwelling unit that is within one-half of one mile walking distance of a major transit stop or a high-quality transit corridor, as those terms are defined in Section 21155 of the Public Resources Code.
1 - 25 feet.
A height of 25 feet or the height limitation in the local zoning ordinance that applies to the primary dwelling, whichever is lower, for an accessory dwelling unit that is attached to a primary dwelling.
1 - 4 feet.
No setback shall be required for an existing living area or accessory structure or a structure constructed in the same location and to the same dimensions as an existing structure that is converted to an accessory dwelling unit or to a portion of an accessory dwelling unit, and a setback of no more than four feet from the side and rear lot lines shall be required for an accessory dwelling unit that is not converted from an existing structure or a new structure constructed in the same location and to the same dimensions as an existing structure.
1 Parking requirements for accessory dwelling units shall not exceed one parking space per accessory dwelling unit or per bedroom, whichever is less.
1- No parking standard within a half mile walk of transit.
Where the accessory dwelling unit is located within one-half of one mile walking distance of public transit.
1 - No replacement parking.
When a garage, carport, covered parking structure, or uncovered parking space is demolished in conjunction with the construction of an accessory dwelling unit or converted to an accessory dwelling unit, the local agency shall not require that those offstreet parking spaces be replaced.
1 - No sprinklers unless the primary home requires them.
Accessory dwelling units shall not be required to provide fire sprinklers if they are not required for the primary residence.
1 - No owner-occupancy requirement on single-family lots; rentals may be limited to 30 days or longer.
No additional standards, other than those provided in Section 66314, shall be used or imposed, including an owner-occupant requirement, except that a local agency may require that the property may be used for rentals of terms 30 days or longer.
1 - 750 square feet.
A local agency, special district, or water corporation shall not impose any impact fee upon the development of an accessory dwelling unit that has 750 square feet of interior livable space or less or a junior accessory dwelling unit that has 500 square feet of interior livable space or less.
1 - Generally cannot be sold separately.
Except as provided in Article 4 (commencing with Section 66340), the accessory dwelling unit may be rented separate from the primary residence, but shall not be sold or otherwise conveyed separate from the primary residence.
1 - 500 square feet.
“Junior accessory dwelling unit” means a unit that is no more than 500 square feet of interior livable space in size and contained entirely within a single-family residence.
1 - JADU owner-occupancy only with shared sanitation.
Owner-occupancy shall not be required if the junior accessory dwelling unit has separate sanitation facilities, or if the owner is another governmental agency, land trust, or housing organization.
1 - Permit for unpermitted pre-2020 ADU cannot be denied for code or ADU-rule violations alone.
Notwithstanding any other law, and except as otherwise provided in subdivision (b), a local agency shall not deny a permit for an unpermitted accessory dwelling unit or an unpermitted junior accessory dwelling unit that was constructed before January 1, 2020, due to either of the following…
1 - State-mandated ministerial approval: one detached new ADU up to 800 sq ft.
One detached, new construction, accessory dwelling unit that does not exceed four-foot side and rear yard setbacks for a lot with a proposed or existing single-family dwelling.
1 - 800 square feet.
A total floor area limitation of not more than 800 square feet of livable space.
1 - HCD lists the handbook as updated March 2026.
ADU Handbook Updated March 2026.
2 - HCD handbook updated March 2026 for the law effective January 1, 2026.
This updated ADU Handbook references the law as amended by recent legislation that went into effect on January 1, 2026.
3
- Applies to
- Applies to all local agencies, general law or chartered1
- Can local rules be stricter?
- Local ordinance that fails the article is void; state standards apply1
New state laws not yet in effect
These California statutes have been enacted but do not apply until the date shown; until then, the law in force applies. Each entry quotes the enacted text.
- Two detached new-construction ADUs allowed on a lot with a single-family home.
Two detached, new construction, accessory dwelling units that do not exceed four-foot side and rear yard setbacks for a lot with a proposed or existing single-family dwelling.
1 Stats. 2026, Ch. 791 (AB 956); in effect from 1 - No junior ADU required on a lot where two detached new ADUs were built.
Notwithstanding subdivision (a), a local agency is not required to ministerially approve an application for a building permit to create a junior accessory dwelling unit on the same lot where two detached, new construction, accessory dwelling units have been constructed pursuant to paragraph (2) of subdivision (a).
1 Stats. 2026, Ch. 791 (AB 956); in effect from 1 - For up to two ADUs on a lot, impact fees only on the area above 750 sq ft.
(B) For up to two accessory dwelling units on a lot, any impact fees charged for an accessory dwelling unit that has more than 750 square feet of interior livable space shall be charged proportionately in relation to the square footage of the primary dwelling unit, and only on the area in excess of 750 square feet of interior livable space.
1 Stats. 2026, Ch. 809 (SB 1117); in effect from 1
Building departments in California
An ADU still needs a building permit from the local department. Our city guides:
Sources
- Government Code Section 66317California Legislature, Legislative Information (leginfo) public data downloadEffective January 1, 2026Checked November 7, 2026
- Accessory Dwelling UnitsCalifornia Department of Housing and Community DevelopmentChecked November 5, 2026
- Accessory Dwelling Unit Handbook, March 2026California Department of Housing and Community DevelopmentPublished March 2026Checked November 5, 2026