Santa Monica regulates ADUs and JADUs in SMMC 9.31.025. On a single-unit dwelling parcel you may establish one converted ADU, one JADU, one detached ADU, and (in the R1 district) one additional attached or detached ADU. Review is ministerial: building permit only, no design review or public hearing.[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 new ADU: studio/one-bedroom up to 850 sq ft; two or more bedrooms up to 1,200 sq ft; minimum 150 sq ft. Converted ADU from existing SUD floor area: up to 50% of the existing primary dwelling or the bedroom caps, whichever is less, with at least 800 sq ft guaranteed. JADU: 150 to 500 sq ft.[2] 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 | Detached ADU: 2 stories or 24 ft. ADU inside an existing or proposed single-unit dwelling: underlying zoning height for the primary dwelling.[2] 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: 4 ft. Not permitted in the required front setback of the zoning district. Detached ADUs must be at least 4 ft from the primary dwelling, measured wall to wall. Existing structures converted in place generally need no new setback.[2] 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 | On-site parking is not required (confirm Coastal Zone rules with the California Coastal Commission if your lot is in the Coastal Zone). Parking removed for an ADU need not be replaced.[2] 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 | No owner occupancy for an ADU. A JADU requires owner occupancy in the main home or the JADU, plus a recorded deed restriction.[2] 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 | Building permit only. Coastal lots may also need a Coastal Development Permit or Waiver. Historic resources on the California Register may have extra standards.[2] 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] |
Also worth knowing: Short-term rentals of 30 days or less are not permitted for ADUs or JADUs.[1]
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Sources
Every fact above links to an official city or state page. Rules change; check the source before you build.
- [1] City of Santa Monica: Accessory Dwelling Units checked Oct 2026
- [2] City of Santa Monica: ADU Guide for Single-Unit Dwelling parcels (Nov 2025) checked Oct 2026
- [3] Santa Monica Municipal Code 9.31.025 checked Oct 2026
- [4] HCD ADU Handbook (March 2026) checked Oct 2026