California ADU Rules: State Law Basics

Where the law lives

ADU law is Government Code Title 7, Division 1, Chapter 13, sections 66310 to 66342. SB 477 added the chapter, effective March 25, 2024. SB 543 then amended it and renumbered some sections, effective January 1, 2026. For example, the old section 66324 is now 66311.5 and the old section 66332 is now 66311.7.

Older articles cite section 65852.2 as the home of these rules. The leginfo page for that section now shows no current text, and section 65852.27 (preapproved plans) now points to Article 2 of Chapter 13 where the bill as passed pointed to section 65852.2. So read the Chapter 13 sections below instead of 65852.2.

Source: https://leginfo.legislature.ca.gov/faces/codes_displayText.xhtml?lawCode=GOV&division=1.&title=7.&part=&chapter=13.&article=; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66311.5; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66311.7; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=65852.2; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=65852.27. Checked 2026-10-22.

Approval is ministerial, with deadlines

Under section 66317(a), an ADU permit application is approved ministerially, with no discretionary review or hearing. Any local ordinance that fails the state rules is void and the state standards apply instead (section 66316).

Review clock, section 66317
Step	Rule
Completeness notice	Within 15 business days of receiving the application. If the agency is late, the application is deemed complete.
Decision	Approve or deny within 60 days of a completed application when a single-family or multifamily home already exists on the lot. If it misses the deadline, the application is deemed approved.
Filed with a new home	The agency may wait for the new home's decision. An applicant-requested delay pauses the 60 days.
Denial	The agency must return written comments listing what is defective and how to fix it.
Appeal	Of an incomplete or denied decision; a final written answer is due within 60 business days of the appeal.

Source: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66317; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66316. Checked 2026-10-22.

What a city or county cannot require

Limits on local ADU rules
Topic	State rule	Section
Extra standards	No standards beyond section 66314 and no owner-occupant requirement. An agency may require rentals of 30 days or longer.	66315
Minimum lot size	Not allowed	66314(b)(1)
Side and rear setbacks	No more than 4 ft for new construction; none for a conversion or a rebuild in the same place and size	66314(d)(7)
Parking	No more than one space per ADU or per bedroom, whichever is less; tandem on a driveway allowed	66314(d)(10)
No parking at all	Within half a mile walking distance of public transit; in a historic district; when the ADU is part of the home or an accessory building; where on-street permits are required but not offered; with a car share within one block	66322(a)
Replacement parking	Cannot be required when a garage, carport or parking space is demolished or converted	66314(d)(11)
Maximum size	Cannot be set below 850 sq ft, or 1,000 sq ft if the ADU has more than one bedroom (interior livable space)	66321(b)(2)
Minimum size	Cannot ban an efficiency unit	66321(b)(1)
Height	Must allow at least 16 ft detached; 18 ft detached near major transit (plus 2 ft to match the roof pitch) or on a multistory multifamily lot; 25 ft or the home's zone height, whichever is lower, for an attached ADU	66321(b)(4)
Sprinklers	Not required if the main home does not need them, and an ADU cannot trigger sprinklers in the existing home	66314(d)(12)
Passageway	No walkway to the ADU can be required	66314(d)(6)

State law also sets outer limits: an attached ADU may be capped at 50% of the existing home, and a detached ADU at 1,200 sq ft (section 66314(d)(4) and (5)). HCD's fact sheet lists the same restrictions.

Source: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66314; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66315; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66321; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66322; https://www.hcd.ca.gov/sites/default/files/docs/planning-and-community/housing-law-fact-sheets.pdf. Checked 2026-10-22.

ADUs a city must always allow

Section 66323 says a local agency must approve, ministerially and in any combination, these units in residential and mixed-use zones:

One ADU and one JADU per single-family lot, inside existing or proposed space (or an existing accessory building), with exterior access and side and rear setbacks sufficient for fire and safety. A conversion of an existing accessory structure may expand up to 150 sq ft, only for entry and exit.
One new detached ADU with setbacks of no more than 4 ft. The agency may cap it at 800 sq ft of livable space and apply the height limits above.
On multifamily lots: ADUs in non-livable space (storage rooms, attics, basements, garages), at least one and up to 25% of existing units.
On a lot with an existing multifamily building: up to eight detached ADUs, not more than the number of existing units. On a lot with a proposed one: up to two.

An agency cannot make you fix nonconforming zoning conditions first, and rentals of these units must be for a term longer than 30 days (section 66323(c) and (e)).

Source: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66323. Checked 2026-10-22.

Impact fees

Section 66311.5(c)(1) says no local agency, special district or water corporation may charge an impact fee for an ADU of 750 sq ft of interior livable space or less, or a JADU of 500 sq ft or less. For a larger ADU, impact fees must be charged in proportion to the main home's square footage.

Connection fees and capacity charges are a separate matter. An ADU or JADU is not a new residential use for those, unless it was built with a new single-family home (subdivision (b)). An ADU or JADU under 500 sq ft also counts as not adding 500 sq ft of assessable space for school fees (subdivision (c)(3)). Other fees follow the general fee-justification rules in Chapters 5 and 7.

Source: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66311.5. Checked 2026-10-22.

JADUs

A junior ADU is no more than 500 sq ft of interior livable space, entirely inside a single-family home (section 66313(d)). If a city allows JADUs, section 66333 lets it require:

One JADU per single-family lot.
Owner occupancy when the JADU shares sanitation with the home. The owner can live in the home or the JADU. It is not required if the JADU has its own bathroom or the owner is a government agency, land trust or housing organization.
A recorded deed restriction that bars selling the JADU separately.
A space within the walls of the home, including an attached garage, with a separate entrance and an efficiency kitchen.
Rentals of the JADU for a term longer than 30 days (section 66333(g)).

A JADU ordinance cannot require additional parking (section 66334(a)). HCD's fact sheet lists the same JADU points.

Source: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66313; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66333; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66334; https://www.hcd.ca.gov/sites/default/files/docs/planning-and-community/housing-law-fact-sheets.pdf. Checked 2026-10-22.

Selling an ADU, and old unpermitted ADUs

An ADU may be rented separately but not sold apart from the main home, except under Article 4 (sections 66340 to 66342) (section 66314(d)(1)). Section 66341 allows a sale to a qualified low- or moderate-income buyer when a nonprofit built the unit. Section 66342 lets a city or county adopt an ordinance allowing the ADU and main home to be sold as condominiums. San Diego County adopted such a program in 2026; see the county guide.

Section 66311.7 bars a local agency from denying a permit for an unpermitted ADU or JADU built before January 1, 2020 because it violates building standards or local ADU rules, unless the agency finds the fix is needed to meet the health and safety standards in Health and Safety Code section 17920.3. It also exempts the homeowner from impact fees, with exceptions, and tells agencies to offer a confidential third-party code inspection before applying. The section was amended by AB 2533 (2024) and renumbered from 66332 by SB 543.

Source: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66314; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66311.7; https://www.hcd.ca.gov/sites/default/files/docs/planning-and-community/housing-law-fact-sheets.pdf. Checked 2026-10-22.

Pre-approved plans

Government Code section 65852.27, added by AB 1332 (2023), requires every local agency to run a program that preapproves ADU plans by January 1, 2025. If a detached ADU application uses a preapproved plan (or one identical to a plan the agency already approved in the current building code cycle), the agency must approve or deny it within 30 days of a completed application. San Diego County says it has offered preapproved plans since 2019. The City of San Diego gives applications with preapproved plans a 30-day review.

Source: https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=65852.27; https://leginfo.legislature.ca.gov/faces/billTextClient.xhtml?bill_id=202320240AB1332; https://www.sandiegocounty.gov/content/sdc/pds/longrangeplanning/ADU-ZO.html; https://www.sandiego.gov/development-services/forms-publications/information-bulletins/400. Checked 2026-10-22.

Recent changes in the HCD fact sheet

SB 1211 (2024): up to eight detached ADUs on a lot with an existing multifamily building (confirmed in section 66323), and no replacement parking when uncovered parking is converted (confirmed in section 66314(d)(11)).
SB 543 (2025): size limits measured as interior livable space, the 15-business-day completeness decision, and clearer impact fee exemptions.
AB 462 (2025): after a declared disaster, a certificate of occupancy for an ADU can issue before the damaged main home (section 66328), and coastal development permit decisions for ADUs follow the 60-day clock without public hearings (section 66329).
AB 2533 (2024): legalizing unpermitted ADUs and JADUs built before January 1, 2020 (section 66311.7, confirmed above).

Source: https://www.hcd.ca.gov/sites/default/files/docs/planning-and-community/housing-law-fact-sheets.pdf (April 2026 edition); https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66328; https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=GOV&sectionNum=66329. Checked 2026-10-22.

What this guide leaves out

Sections of Chapter 13 not summarized here, such as the remaining general provisions and the coastal zone rules beyond the review deadline.
Local rules differ. Anything in this guide is a state floor and ceiling, not what your city or county will accept in practice.
The law changes, often on January 1. Confirm the current section text on leginfo or with your permit office.

Next, read your local rules: City of San Diego or San Diego County. To test an ADU as a rental, run the rental cash flow calculator.

FAQ

Can a city make me provide parking for an ADU?

Sometimes one space, but not within half a mile of public transit, in a historic district, or when the ADU is part of the existing home. It also cannot require replacement parking when a garage becomes an ADU (sections 66314 and 66322).

Do I pay impact fees on a small ADU in California?

Not on an ADU of 750 square feet or less, or a JADU of 500 square feet or less. Larger ADUs are charged in proportion to the main home (section 66311.5).

How long does the city have to decide on my ADU permit?

Fifteen business days to say whether the application is complete, then 60 days to approve or deny a completed application. A missed deadline means deemed approved (section 66317).

Can I use my ADU as a short-term rental?

Local agencies may limit it, and for certain ADUs state law requires rentals longer than 30 days (sections 66315 and 66323). Check your local rule.