Berkeley sets ADU standards in Municipal Code Chapter 23.306. Limits differ inside and outside the Hillside Overlay.[1]
What is an ADU? An accessory dwelling unit is a small second home on the same lot as the main house: a backyard unit, garage conversion, attached addition or guest house with its own kitchen and bath.
California cities can set their own ADU rules, but never stricter than state law. Grey lines show the state floor from the HCD ADU Handbook.
| Size limits | Outside the Hillside Overlay: max 1,200 sq ft gross floor area. Inside the Hillside Overlay: 850 sq ft for a studio or one bedroom, 1,000 sq ft for two or more bedrooms. A conversion that already exceeds those caps may add at most 150 sq ft, and the addition must meet height and setback rules. JADU: up to 500 sq ft entirely within the single-family dwelling or its attached garage.[1] State law: a city's maximum size must allow at least 850 sq ft, or 1,000 sq ft for more than one bedroom, and local rules cannot block an 800 sq ft ADU with 4 ft side and rear setbacks (Gov. Code 66321).[4] |
|---|---|
| Height | Outside Hillside Overlay, new detached or attached: 25 ft. Inside Hillside Overlay: detached 20 ft; attached 25 ft or the existing building height limit, whichever is lower. Conversions keep the existing structure height.[1] State law: detached ADUs get at least 16 ft; 18 ft within a half mile walk of a major transit stop or high-quality transit corridor (plus 2 ft to match roof pitch) or on a lot with a multistory multifamily building; attached ADUs up to 25 ft or the main home's limit if lower (Gov. Code 66321).[4] |
| Setbacks | Minimum 4 ft rear, interior side and street side. Detached ADUs may use a lesser setback if the comparable accessory building standard in 23.304.060 allows it.[1] State law: side and rear setbacks can be no more than 4 ft for new ADUs; converted existing space needs no new setback (Gov. Code 66314, 66323).[4] |
| Parking | Required off-street parking for ADUs follows BMC 23.322.030. Check that section and the city ADU info sheet for your lot.[1] State law: at most 1 space per ADU or per bedroom, whichever is less, and none within a half mile walk of public transit, in a historic district, within one block of a car share, or for ADUs inside the house (Gov. Code 66314, 66322).[4] |
| Owner occupancy | A JADU that shares a bathroom with the main home needs an internal connection to the main living area.[1] State law: no owner occupancy requirement for ADUs (Gov. Code 66315). A JADU requires the owner to live on site if it shares a bathroom with the main home (Gov. Code 66333).[4] |
| Permit steps and timeline | No city-specific figure verified. The state minimum below applies; confirm local details with the city. State law: the city must approve or deny a complete application within 60 days when there is an existing home on the lot (Gov. Code 66317).[4] |
| Fees | No city-specific figure verified. The state minimum below applies; confirm local details with the city. State law: no impact fees on ADUs of 750 sq ft or less; above that, impact fees must be proportional to the size of the main home. Plan check, permit and school fees can still apply.[4] |
We connect you with builders from this directory who serve your area. Free, no obligation.
Sources
Every fact above links to an official city or state page. Rules change; check the source before you build.
- [1] Berkeley Municipal Code 23.306.030 (ADU Development Standards) checked Oct 2026
- [2] City of Berkeley: Residential Additions and Accessory Dwelling Units checked Oct 2026
- [3] City of Berkeley: ADU Information Sheet checked Oct 2026
- [4] HCD ADU Handbook (March 2026) checked Oct 2026