Accessory Dwelling Unit (ADU) Rules in California
A secondary living unit on the same lot as a primary home, such as a garage conversion, basement apartment or detached backyard cottage.
What the state law requires
Cities and counties must ministerially approve an accessory dwelling unit up to at least 800 square feet with four-foot side and rear setbacks. Detached units may reach at least 1,200 square feet. Agencies may not require owner occupancy, and may not require parking when the unit is within one-half mile of a public transit stop. Approval must occur within 60 days of a complete application.
Citation: Cal. Gov. Code §§ 66310–66342 (ADU law, formerly § 65852.2) · https://leginfo.legislature.ca.gov/ · Retrieved 2026-08-29
State law usually sets the floor for what local governments must allow. Your city or county can still apply objective standards, so confirm the local rules as well.
Get a checklist for your address
Questions to ask your local department
- Ask the local planning or building department whether a state ADU statute applies to your parcel and whether the city has a conforming local ordinance.
- Request the objective standards used for ministerial review: size cap, height, setbacks and lot coverage.
- Confirm utility connection requirements and any separate metering rules.
- Ask whether owner occupancy, short-term rental use, or parking is regulated for your unit type.
Back to Accessory Dwelling Unit (ADU) rules or the yard rules hub.
Accessory Dwelling Unit (ADU) in California: common questions
Does California have a statewide accessory dwelling unit (adu) law?
Cities and counties must ministerially approve an accessory dwelling unit up to at least 800 square feet with four-foot side and rear setbacks. Detached units may reach at least 1,200 square feet. Agencies may not require owner occupancy, and may not require parking when the unit is within one-half mile of a public transit stop. Approval must occur within 60 days of a complete application.
Does the state law replace my city or county rules?
Usually it sets a floor, not a ceiling. A statewide statute typically tells local governments what they must allow, while your city or county can still apply objective standards such as setbacks, height and utility connections. Local rules cannot usually contradict the state mandate, but they can add reasonable requirements.
What should I confirm locally before I start?
Ask the local planning or building department whether a state ADU statute applies to your parcel and whether the city has a conforming local ordinance. Request the objective standards used for ministerial review: size cap, height, setbacks and lot coverage. Confirm utility connection requirements and any separate metering rules. Ask whether owner occupancy, short-term rental use, or parking is regulated for your unit type.
ZoneFig provides general reference information, not legal advice. Yard and zoning rules are adopted locally, so the only binding answer for your address comes from your city, town or county planning and building department. Typical thresholds shown here describe patterns across many jurisdictions and are not the rule at any specific property.