ADU Cost & Rules in San Diego, CA
Planning an accessory dwelling unit in San Diego? 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)
- Setbacks
- 4 ft side and rear
- Owner-occupancy required
- Not required
- Typical permit & city fees
- $10,000 – $15,000
- Typical timeline (design → done)
- 6–12 months
How much does an ADU cost in San Diego?
A detached new-build ADU in San Diego typically costs $250,000 – $400,000, while a garage conversion runs $120,000 – $180,000. Permit and city fees add $10,000 – $15,000, and most projects take 6–12 months from design to completion.
Do you need a permit to build an ADU in San Diego?
Yes. Every ADU in San Diego requires building permits, with typical city and permit fees of $10,000 – $15,000. Setback requirements are 4 ft side and rear, and owner occupancy is not required.
How big can an ADU be in San Diego?
ADUs in San Diego can be up to 1200 sq ft. No minimum lot size (state law). Local note: ADUs under 750 sq ft are exempt from development impact fees — often a $5,000+ saving. Properties in the Coastal Overlay Zone may need a Coastal Development Permit, adding 2–4 months. New utility connections can add $7,000+ in capacity charges.
Cost breakdown for San Diego (2026)
- Detached new-build ADU
- $250,000 – $400,000
- Garage conversion
- $120,000 – $180,000
Local note: ADUs under 750 sq ft are exempt from development impact fees — often a $5,000+ saving. Properties in the Coastal Overlay Zone may need a Coastal Development Permit, adding 2–4 months. New utility connections can add $7,000+ in capacity charges.
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 Diego planning department before designing. Last reviewed 2026.