ADU rules in California
Representative cities: Los Angeles, San Francisco, San Diego.
ADU permit rule
Permit requiredGenerally allowedcity authority
Fee basis
Permit and plan-check fees set by the local jurisdiction; state law limits impact fees on ADUs. Verify with the city building department.
Typical timeline
~3–6 months for full plan review; many cities offer pre-approved plans or over-the-counter review.
Setback
State standard: 4 ft side/rear setback; local front/side yards still apply.
Area threshold
By-right up to 1,200 sq ft (≤800 sq ft for a 1-bedroom unit) under state law.
Exempt if
None — ADUs always require a building permit.
Go / no-go
allowed
State law (Gov. Code §65852.2) requires cities to approve ADUs ministerially by right in most zones; local design review is limited to objective standards. Local fees, setbacks, and coastal/historic overlays still apply.
🧮
Estimate build cost
Model this ADU's construction cost by type, size & finish.
📊
Model rental ROI
Turn the build cost into rent, payback & 20-year cash flow.
Frequently asked questions
Do I need a permit to build an ADU in California?
Per California rules, an ADU is "yes" for a permit and the authority is "city". State law (Gov. Code §65852.2) requires cities to approve ADUs ministerially by right in most zones; local design review is limited to objective standards. Local fees, setbacks, and coastal/historic overlays still apply. Always confirm with the issuing building department.
How big can an ADU be in California?
Area threshold: By-right up to 1,200 sq ft (≤800 sq ft for a 1-bedroom unit) under state law.
What are the ADU setbacks in California?
Setback: State standard: 4 ft side/rear setback; local front/side yards still apply.
How much does an ADU permit cost in California?
Fee basis: Permit and plan-check fees set by the local jurisdiction; state law limits impact fees on ADUs. Verify with the city building department.