Santa Rosa allows ADUs on lots that permit single-family or multifamily dwellings (including RR, R-1, R-2, R-3 and TV-R). They are not allowed in MH zones. A building permit with ministerial planning approval is required.[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 | Detached ADUs: up to 1,200 sq ft per local rules summaries that cite the city ordinance. State law still guarantees at least an 800 sq ft ADU with 4 ft side and rear setbacks. Confirm the current size table on the city checklist before you design.[2][3] 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 | No city-specific figure verified. The state minimum below applies; confirm local details with the city. 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 | Side and rear setbacks of 4 ft for the statewide floor. Confirm front setback and any local extras on the city checklist.[2][3] 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 | No city-specific figure verified. The state minimum below applies; confirm local details with the city. 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 | ADUs cannot be sold separately from the primary residence. Rentals under 30 days are not allowed. ADUs are not permitted on or adjacent to California Register of Historic Places properties per the ordinance packet.[3] 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 | Complete applications must be decided within 60 days under the city ordinance materials. Use the ADU Requirements and Application Checklist when you prepare plans.[3][1] 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] City of Santa Rosa: ADU Requirements and Application Checklist checked Oct 2026
- [2] Napa Sonoma ADU Center: City of Santa Rosa local rules checked Oct 2026
- [3] Santa Rosa ADU Ordinance (2020) checked Oct 2026
- [4] HCD ADU Handbook (March 2026) checked Oct 2026