California ADU laws in 2026, in plain English

ADU or junior ADU

An accessory dwelling unit is an attached or detached home on the same lot as a house, with its own permanent place to live, sleep, eat, cook and wash. It can be a new backyard cottage, an addition, or a converted garage or basement.

A junior ADU (JADU) is a unit of no more than 500 square feet of interior space carved out of a single-family house, which includes an attached garage. It needs at least an efficiency kitchen, and can share a bathroom with the house. There's one JADU per single-family lot at most.

Since January 1, 2026, sizes are measured as interior livable space: rooms for living, sleeping, eating, cooking or washing, including closets and interior stairs.

How many units you can build

On a single-family lot every city must approve, together:

• one ADU converted from space inside the house or an existing accessory building,
• one new detached ADU of up to 800 square feet with 4-foot side and rear setbacks, and
• one junior ADU.

That's up to three extra homes alongside the house. On a lot with an existing apartment building, owners can add up to eight detached ADUs (no more than the number of existing units), plus conversions of non-livable space like storage rooms and garages for up to a quarter of the units.

Size, height and setbacks

Converting space that already exists isn't subject to size limits, and a converted accessory building can grow by up to 150 square feet for an entrance.

The 60-day permit clock

ADU permits are ministerial: no hearing and no neighbor vote. Since 2026 the city has 15 business days to tell you whether your application is complete, or it's deemed complete. It then has 60 days to approve or deny. If it does neither, the permit is deemed approved. A denial must come with written comments explaining how to fix the application, and you have the right to appeal.

Parking

A city can't require any parking for an ADU that is:

• within half a mile walking distance of public transit, which includes a bus stop,
• in a historic district,
• part of the house or an existing accessory building,
• on a street that requires permits the ADU's tenant can't get, or
• within one block of a car-share vehicle.

Where parking can be required, it's one space at most, and a driveway space counts. If you convert or tear down a garage, carport or uncovered space for an ADU, the city can't make you replace that parking.

Living there, renting and selling

ADUs: no city may require the owner to live on the property. You can rent the ADU separately from the house, and a city may require rentals to be longer than 30 days, so no short-term vacation rentals.

Junior ADUs: since 2026 the owner has to live on site only if the JADU shares a bathroom with the house. JADUs can't be rented for 30 days or less, and can never be sold separately.

Selling an ADU on its own is possible only where the city has opted in to condominium sales. Every lender with a loan on the property must agree. The City of San Diego has opted in.

Fees the law limits

• Impact fees: none for an ADU of 750 square feet or less. Above that, fees must be proportional to the size of the main house.
• School fees: none for an ADU or JADU under 500 square feet.
• Utility connections: an ADU converted from existing space can't be made to install a new connection or pay a connection fee, unless it's built with a new house. Other ADUs can be charged, in proportion to their size or plumbing fixtures.

See what an ADU costs in San Diego for the fees you'll actually pay.

Unpermitted ADUs

If you have an ADU built without permits before January 1, 2020, the city can't refuse to permit it just because it breaks building or zoning rules, unless a fix is needed for health and safety. It also can't charge impact fees or penalize you for having it. San Diego explains the process in Information Bulletin 242.

City of San Diego rules

San Diego's code follows state law and is more generous in places:

• Size: 150 to 1,200 square feet for an ADU; conversions inside existing buildings have no maximum. JADUs run 150 to 500 square feet.
• Setbacks: an ADU 16 feet tall or less needs no interior side or rear setback, except in high and very high fire hazard zones, where it's 4 feet.
• Parking: none required, except in the Beach Impact Area outside transit priority areas.
• Rentals: at least 31 consecutive days.
• Impact fees: the first two ADUs on a property are exempt, whatever their size.
• Coastal zone: most ADUs need a Coastal Development Permit; state law requires a decision within 60 days.

The city's ADU Home Density Bonus, which allows extra ADUs in exchange for affordable ones, was cut back in 2025. Total units on a single-family lot are now capped at 4 to 6 depending on lot size, and the program is closed in several single-family zones.

What changes in 2027

Two bills signed on September 29, 2026 take effect on January 1, 2027:

• AB 956: cities must approve two new detached ADUs on a single-family lot, up from one.
• SB 1117: for ADUs over 750 square feet, impact fees are charged only on the area above 750.

We'll update this guide when the state's ADU handbook covers them.

Common questions