ADU Cost & Rules in San Francisco, CA
Planning an accessory dwelling unit in San Francisco? Here are the current construction cost ranges, permit fees, and the zoning rules that apply to most residential lots — compiled from city and state requirements and 2026 regional cost data.
- Maximum ADU size
- 1200 sq ft
- Minimum lot size
- No minimum lot size (state law); local program units often capped at 850–1,000 sq ft
- Setbacks
- 4 ft side and rear
- Owner-occupancy required
- Not required
- Typical permit & city fees
- $5,000 – $20,000
- Typical timeline (design → done)
- 10–18 months
How much does an ADU cost in San Francisco?
A detached new-build ADU in San Francisco typically costs $250,000 – $450,000, while a garage conversion runs $120,000 – $250,000. Permit and city fees add $5,000 – $20,000, and most projects take 10–18 months from design to completion.
Do you need a permit to build an ADU in San Francisco?
Yes. Every ADU in San Francisco requires building permits, with typical city and permit fees of $5,000 – $20,000. Setback requirements are 4 ft side and rear, and owner occupancy is not required.
How big can an ADU be in San Francisco?
ADUs in San Francisco can be up to 1200 sq ft. No minimum lot size (state law); local program units often capped at 850–1,000 sq ft. Local note: The most expensive major California market: detached builds run $350–$500 per sq ft, and the median permit timeline is around 186 days. Impact fees are waived under 750 sq ft, and pre-approved plans can save $3,000–$10,000 in design costs and 2–3 months of review.
Cost breakdown for San Francisco (2026)
- Detached new-build ADU
- $250,000 – $450,000
- Garage conversion
- $120,000 – $250,000
Local note: The most expensive major California market: detached builds run $350–$500 per sq ft, and the median permit timeline is around 186 days. Impact fees are waived under 750 sq ft, and pre-approved plans can save $3,000–$10,000 in design costs and 2–3 months of review.
Get an estimate for your project
Ranges above assume typical lots and standard finishes. For a number tailored to your size, type, and finish level, run the calculator:
Open the ADU Cost Calculator →Figures reflect published city fee schedules and 2026 regional construction data; rules change — confirm with the San Francisco planning department before designing. Last reviewed 2026.