ADU Builders in San Francisco: Costs and Permits
ADUs in San Francisco
The city issued 223 permits for ADU projects of all property types over the last 12 months; the median estimated construction cost on one- and two-family homes was $100,000.
San Francisco at a glance
- Issued ADU permits, all property types, last 12 months
- 223 permits
- Share of issued ADU permits on one- or two-family dwellings, last 12 months
- 77.6%
- Median estimated construction cost, ADU permits on one- and two-family homes, last 12 months
- $100,000
San Francisco Department of Building Inspection, Building Permits (DataSF) · data as of
- Numbers from SF DBI, HCD and US Census public records
- Up to three local contractors, never a long list
- Free, no obligation
San Francisco ADU permits and housing facts
San Francisco ADU permits and housing facts
Local numbers for San Francisco, each with its source and date.
- Median days from filing to issue, ADU permits on one- and two-family homes, last 12 months1
- 204 days
- ADU units with building permits issued in 2025, San Francisco, as reported so far2
- 171
- ADU units completed in 2025, San Francisco, as reported so far2
- 218
- Share of San Francisco housing units built before 1980, 2020–20243
- 76.5%
- Median year structure built, San Francisco housing units, 2020–20243
- 1946
- Share of occupied San Francisco housing units that are owner-occupied, 2020–20243
- 38.2%
- Median value of owner-occupied homes in San Francisco, 2020–20243
- $1,394,500
Planning your project
What San Francisco's homes mean for your ADU
In San Francisco, the Department of Building Inspection issued 223 permits for ADU projects over the last 12 months, all property types. Of those, 77.6% were on one- or two-family dwellings, and the median estimated construction cost on those permits was $100,000.
Most homes here are older. 76.5% of San Francisco housing units were built before 1980, and the median year built is 1946 (Census 2020–2024). An older main house can share its electrical panel, water and sewer lines with a new unit, so ask your builder to check their capacity. If you convert an old garage, plan for lead-based paint testing on structures built before 1978 and check for possible asbestos in old materials. These are things to check, not certainties for every house.
Only 38.2% of occupied San Francisco homes are owner-occupied, so many homes are rentals. If you own a rental, plan the work around your tenants' schedule and think about what the project means for the rental. The median value of owner-occupied homes is $1,394,500 (Census 2020–2024). Compare any budget with the likely resale value in general terms.
The city's state report counts 171 ADU units with permits issued in 2025 and 218 units completed in 2025, both as reported so far. These are units, not permits, and the counts may still rise.
What the permit figure measures
| Project | Figure | Range on a shared scale |
|---|---|---|
| Median estimated construction cost, ADU permits on one- and two-family homes, last 12 monthsEstimated cost written on the permit application, not a contract price or quote. | $100,000 |
Bars share one scale, from $0 to $100,000.
The figure is the median estimated construction cost written on San Francisco permit applications for one- and two-family homes over the last 12 months. It is not a contract price. The real project cost is often higher because of design, finishes, work not on the permit, and the home's condition. Get an estimate for your home to know your number.
The typical path for an ADU in San Francisco
The typical path for an ADU in San Francisco
Check what your lot allows
Ask the city which rules apply to your lot and building. Confirm the details with your builder before you commit to a design.
Design and plans
Your builder drafts plans for the unit. Include the capacity of the existing electrical panel and the water and sewer lines in the plans.
Plan check and permit
The Department of Building Inspection reviews the plans before a permit is issued. For one- and two-family homes, the median time from filing to issue was 204 days over the last 12 months, so plan ahead.
Construction and inspections
Work is inspected at set stages. For an older home, test for lead-based paint if you convert a structure built before 1978, and watch for possible asbestos in old materials.
Final sign-off
After the inspections pass, the permit can receive final sign-off. Ask your builder to confirm the final steps and paperwork.
Questions homeowners ask about ADUs in San Francisco
Do I need a permit for an ADU?
Most ADU projects in San Francisco go through a city permit. Confirm the rules for your property with the Department of Building Inspection and your builder.
Why do older homes matter for an ADU?
76.5% of San Francisco housing units were built before 1980, and the median year built is 1946 (Census 2020–2024). Check the electrical panel and the water and sewer lines before you design the unit.
What does an ADU cost?
The median estimated construction cost on ADU permits for one- and two-family homes was $100,000 over the last 12 months. That figure is an estimate on the permit application, not a contract price. Real costs are often higher, so get an estimate for your home.
How long do ADU permits take?
The median time from filing to issue was 204 days for ADU permits on one- and two-family homes over the last 12 months. Timing varies by project, so ask your builder and the city.
How do I start?
Check what your lot allows, then send a request for a free estimate. The request goes to one local builder. You can check any contractor's license status with the CSLB (Contractors State License Board).
Recent work by a contractor in our network
Photos from the contractor's own projects, used with permission. Captions name the type of work.
Bathroom in an ADU 
Addition / ADU interior 
Addition / ADU interior 
Addition / ADU bathroom
Ask a local builder for a free estimate for your ADU
Tell us about the project. It takes about 30 seconds.
- You send a short request. Project type, ZIP code, timing and how to reach you.
- We match it. A local contractor for your project gets your request. Up to three may contact you, and we email you each one's name.
- You talk about your project. The estimate is free, with no obligation to hire.
Thanks — your request is in.
We're matching your project now. When a contractor takes it, we email you their name and phone number so you know who is calling.
We're matching your project now. A local contractor will call you at the number you gave us to talk about the next step.
Who gets your request
Your local match
Your project · works in San Francisco
Matched to your project. We check the project type and ZIP first. Up to three local contractors may contact you, and we email you each one's name.