Ministerial approval — no hearings
Qualifying ADUs must be approved ministerially. That means a permit technician checks the plans against objective standards and issues the permit. There is no design review board, no discretionary hearing, no neighbor comment period and no CEQA review. If a planner tells you your ADU is going to a hearing, that is a red flag worth challenging in writing.
The clock is 60 days from a complete application. If the jurisdiction fails to act within 60 days, the application is deemed approved by operation of law.
Size, setbacks and height floors
| Standard | State floor |
|---|---|
| Any ADU | 800 sq ft must be allowed regardless of lot coverage or FAR |
| One bedroom | At least 850 sq ft |
| Two or more bedrooms | At least 1,000 sq ft |
| Side and rear setback | No more than 4 feet required |
| Detached height | At least 16 ft; 18–25 ft in defined transit and multistory cases |
| Conversion of existing space | No new setback required for the existing footprint |
Parking, owner-occupancy and HOAs
- No parking may be required within half a mile walking distance of public transit
- Replacement parking cannot be demanded when a garage is converted to an ADU
- Owner-occupancy cannot be imposed on standard ADUs; junior ADUs are the exception
- HOA rules that effectively prohibit ADUs on single-family lots are unenforceable
- Short-term rentals under 30 days may be restricted locally — this is where cities still have teeth
Utilities and fees
For an ADU converted within an existing single-family home, a city cannot require a separate utility connection or charge connection and capacity fees. For new detached construction, a separate connection may be required, but fees must be proportional to the burden — typically calculated on square footage or fixture count rather than as a flat single-family charge.
Impact fees cannot be charged at all on ADUs under 750 sq ft. Above that threshold they must be proportional to the primary dwelling. This is the single most useful threshold in the statute for planning purposes.
Where cities still have real authority
Objective design standards — materials, roof pitch, window placement — remain enforceable if they are truly objective and do not physically preclude an 800 sq ft unit. Fire sprinkler requirements apply where the primary dwelling has them. Building code, energy code and health-and-safety requirements apply in full. And in genuine high-fire-severity or flood zones, additional siting constraints are legitimate.
None of this is legal advice. Statutes get amended most years, and local implementation varies. We confirm the current rules for your parcel during feasibility and put them in writing before you spend money on design.