As of November 2026, California law requires cities to approve qualifying ADUs ministerially, within 60 days of a complete application. It caps side and rear setbacks at 4 feet, guarantees at least 16 feet of height for a detached unit, bans owner-occupancy rules for ADUs, and waives impact fees for units of 750 square feet or less. San Francisco applies these state rules alongside its own local standards.
How big can an ADU be?
Cities must allow at least 850 square feet, or 1,000 square feet for an ADU with more than one bedroom, measured as interior livable space. Where no compliant local ordinance exists, the default cap for a new detached ADU is 1,200 square feet. A junior ADU is limited to 500 square feet. Conversions of existing space are treated more flexibly.
How close to the property line?
No more than 4 feet can be required for side and rear setbacks on a new unit, and none for an ADU built inside an existing structure or in the same footprint. Fire and building code separations still apply.
How tall?
- Detached: at least 16 feet, more near major transit or on some multifamily lots.
- Attached: at least 25 feet or the height limit for the main home, whichever is lower.
- Conversions: the height of the existing structure.
How many units can go on my lot?
On a single-family lot, state law allows a combination of a converted ADU, a junior ADU and a new detached ADU, subject to its conditions. Multifamily lots have separate allowances.
Parking, owners and rentals
- No replacement parking when a garage is converted or demolished for an ADU.
- No parking requirement within half a mile walking distance of public transit, among other exemptions.
- No owner-occupancy requirement for ADUs. For a junior ADU that shares a bathroom with the house, a city can require the owner to live on site.
- Rentals of state-guaranteed ADUs and JADUs must be longer than 30 days.
What about San Francisco?
San Francisco applies state law through its State ADU Program and offers a separate Local Program with different unit counts and waivers. Planning also notes that an ADU applied for on or after May 1, 2025, on a lot with four or fewer existing units, can be eligible for condominium sale under the State Program. Confirm eligibility with Planning.
Sources, as of November 2026: California Government Code section 66310 and following (ADU law), including SB 543 (2025); California Department of Housing and Community Development, ADU Handbook. General information, not legal advice. San Francisco Planning, "Accessory Dwelling Units".
Updated November 2026