San Francisco / ADU construction
ADU Construction in San Francisco
San Francisco added 1,354 ADUs from 2021 to 2025. Yours starts with choosing the right program.
Most San Francisco ADUs are carved out of garages, basements and ground floors of flats and apartment buildings. We design and build them here with the program choice, tenant notices and fire review planned before a floor plan is drawn.
PLANNING DIRECTOR BULLETIN NO. 3
State program or Local program.
San Francisco runs two ADU programs for single-family buildings. The State program trades flexibility for speed; the Local program allows waivers on existing buildings but adds Planning review and tenant notice.
| State program | Local program | |
|---|---|---|
| Review | Ministerial, 60 days from a complete application | Planning review first, then DBI |
| Detached ADU size, single-family lot | 850 sq ft studio or 1 bedroom, 1,000 sq ft 2+ bedrooms | Planning Code standards, waivers possible |
| Units on a single-family lot | One detached, one conversion and one junior ADU | 1 ADU plus 1 detached ADU (4 or fewer units) |
| Tenant notice | Not required | Posted 15 days before applying, filed with the Rent Board |
| Past evictions | Do not block the ADU | Owner move-in in 5 years or no-fault in 10 years blocks it |
| Appeals | None for permits filed on or after January 1, 2024 | Standard Planning process |
Source: SF Planning, Planning Director Bulletin No. 3 and ADU program page ↗
STATE PROGRAM OR LOCAL PROGRAM
Two programs, different trade-offs.
Under the State ADU Program a detached ADU on a single-family lot can reach 850 square feet as a studio or one bedroom and 1,000 square feet with two or more bedrooms, at 18 feet plus 2 feet to match the roof pitch. Review is ministerial and limited to 60 days. The Local Program goes through Planning first, takes longer, but allows Planning Code waivers for existing buildings.
Garage and ground-floor conversion
The most common San Francisco ADU. A converted ADU has no size limit, but a ground-floor unit sharing a single exit may need sprinklers or a second exit.
Detached backyard ADU
850 or 1,000 square feet on a single-family lot under the State program, 4 foot side and rear setbacks, 18 feet plus 2 for roof pitch.
Attached ADU
850 or 1,000 square feet, or 50 percent of the main home if larger, up to 25 feet high. Cannot be combined with other ADU types.
Junior ADU
Up to 500 square feet inside a single-family home. If it shares a bathroom, a deed restriction requires the owner to live on site.
ADUs in apartment buildings
Conversions of up to 25 percent of existing units, plus up to 8 detached ADUs on a lot with an existing multifamily building, not exceeding the unit count.
Legalizing an existing unit
San Francisco's legalization program lets owners register an unwarranted unit and bring it up to safety standards through DBI.
SAN FRANCISCO AT A GLANCE
Who does what on a San Francisco ADU.
San Francisco is a city and county in one, so Planning, DBI, SF Fire, the Rent Board, Public Works and the SFPUC can all touch the same ADU. Here is where each one comes in.
- 1,354
- ADUs added or legalized in San Francisco, 2021 to 2025
- 223
- ADUs added in 2025, per the city's Housing Inventory
- 60
- days for a State program ADU review once the application is complete
Planning
SF Planning ADU staff
Program choice, Planning Code waivers and historic review for Local program projects. ADU planners answer questions at CPC.ADU@sfgov.org.
SF Planning ADU program ↗Permits
DBI and PermitSF
Applications go through the PermitSF portal with electronic plans, a Back Check page and the 60-day tolling declaration. The Permit Center help desk is on the 2nd floor at 49 South Van Ness.
(628) 652-3200ADU building permit steps ↗Tenants
Rent Board notice
For Local program ADUs in occupied buildings, the notice and owner declaration are filed with the Rent Board before Planning accepts the application. Tenants have 30 calendar days to object.
Rent Board ADU notice rules ↗Fire and water
SF Fire and SFPUC
SF Fire reviews fire flow and exits; the SFPUC fixture count form is needed when fixtures or a new water service are added. PG&E delivers power and gas, and CleanPowerSF is the city's default electricity provider.
SF Fire ADU checklist ↗
Planning the work
How a San Francisco ADU gets built.
Site check
Free visit. Building type, existing units, exits, eviction history and whether State or Local rules fit.
Program and design
Program chosen, tenant notice posted if Local, fire flow data requested, plans drawn by a licensed professional.
Permit and review
Submittal through PermitSF, the 60-day tolling declaration, and a virtual Permit Review Roundtable for State projects.
Build and final
Framing, rough-in inspections, separate trade finals, then the building final and the job card closed.
WHAT SLOWS ADUS IN SAN FRANCISCO
Problems San Francisco owners run into, and how we plan around them.
From local reporting and the city's own ADU, fire and permit pages. Most delays come from the building around the ADU, not the ADU itself.
Fire and life safety work was skipped, and the unit fails later.
A Noe Valley ADU passed inspection but had no sprinkler or fire alarm permit on record. Fire permits are pulled with the building permit, never after.
A ground-floor unit shares the only exit with the rest of the building.
Exits are checked at the site visit; the choice between a full sprinkler system and a second exit is made before design.
Tenants object, and the Rent Board clock adds months.
For Local program projects the 15-day notice goes out early, and the State program is compared first, since it needs no notice.
Hydrant flow data is out of date when plans are submitted.
SF Fire accepts data less than a year old, so the request goes in at the start of design, not at submittal.
Waivers bring rent control the owner did not expect.
Whether a Costa-Hawkins agreement would apply is explained before choosing the Local program.
Street, sidewalk or sewer work adds Public Works permits and fees.
Utility routes are walked at the site visit and the right-of-way permit is lined up with the building permit.
Sources: SocketSite, September 2021; Mission Local, February 2025; sf.gov ADU and Rent Board pages; SF Fire ADU checklist and Information Sheet EG-05.
BEFORE YOU APPLY
What San Francisco asks for.
Documents to gather
- Plans by a licensed design professional, with a Back Check page
- ADU screening form and Rent Ordinance affidavit
- Permit Application Processing Time Tolling Declaration
- SF Fire water flow request and fire flow study
- SFPUC fixture count form if fixtures are added
The State program fits when
- The ADU meets the 850 or 1,000 sq ft and 18 foot limits
- No unrelated construction is bundled into the permit
- Planning Code waivers are not needed
- The owner wants the 60-day ministerial review
Expect a longer path when
- The building has tenants and the Local program is used
- The property is a historic resource
- Soil disturbance of 50 cubic yards or more triggers Maher review
- A Site permit is chosen instead of a Full permit
How big can a detached ADU be in San Francisco?
Up to 850 square feet for a studio or one bedroom and 1,000 square feet for two or more bedrooms on a single-family lot under the State ADU Program. Height is 18 feet, plus 2 feet to match the main roof pitch, with 4 foot side and rear setbacks. On a lot with a multifamily building there is no maximum size for a detached ADU.
What is the difference between the State and Local ADU programs in San Francisco?
State program ADUs get a ministerial review within 60 days of a complete application, with no discretionary review or appeals. Local program ADUs go through Planning first and need a Planning Approval Letter, but can use Planning Code waivers on existing buildings. The State program is generally faster.
Are new ADUs in San Francisco under rent control?
Yes, in some cases. When a Local program ADU uses Planning Code waivers, the city may require a Costa-Hawkins Regulatory Agreement that places the new unit under rent control, signed before the permit is issued. SF Planning notes that some State program ADUs may be shielded from rent stabilization.
Can I add an ADU to a building with tenants in San Francisco?
Yes. Under the Local program the owner posts and delivers a Notice of Addition and a Declaration to every unit at least 15 calendar days before applying, and tenants have 30 calendar days to object at the Rent Board. Lots with an owner move-in eviction in the past 5 years, or another no-fault eviction in the past 10, cannot use the Local program; evictions do not block State ADUs.
Do I need a fire flow study for an ADU in San Francisco?
Yes, for new construction or added floor area. SF Fire requires a calculation showing the water supply meets California Fire Code Section 507 and Appendix B, using hydrant flow data less than one year old. A ground-floor ADU that shares a single exit may also need a sprinkler system or a second exit.
Are there impact fees for an ADU in San Francisco?
No, not for an ADU under 750 square feet of interior livable space. Above that, fees are proportional to the floor area of the main home. The SFUSD school impact fee is handled separately, at 135 Van Ness Avenue, Room 116.
