ADU Builders in San Francisco, CA (2026)

ADU builders in San Francisco typically quote $300,000-$550,000 for a new detached unit, or about $350-$650 per square foot, including design, permitting, and construction. A garage conversion runs $120,000-$300,000 and a prefab/modular ADU averages $180,000-$350,000. Add city permit and plan-review fees (Planning Department building-permit review (Fee Schedule effective August 29, 2025, revised June 15, 2026): new construction $3,502 under $100,000; $3,504 plus 3.855% of cost above $100,000 up to $499,999; $19,226 plus 1.230% above $500,000. Alteration or conversion: $504 under $10,000; $516 plus 5.274% above $10,000; $3,838 plus 3.524% above $50,000; $5,638 plus 3.855% above $100,000; back-check $366. DBI building permit (Building Code Table 1A-A, permits issued on or after July 12, 2026): plan review $1,617 plus $15.60 per $1,000 over $50,000, or $4,011 plus $13.31 per $1,000 over $200,000; permit issuance $677 plus $4.83 per $1,000 over $50,000, or $1,402 plus $4.21 per $1,000 over $200,000; plumbing, electrical, mechanical, Fire, Public Works and Public Health fees are extra (Table 1A-A note 1). SFUSD school facility fee $3.79 per sq ft of added habitable area (2026 Impact Fee Register). Worked example (our calculation, not a published figure): a $300,000 detached ADU pays about $11,214 to Planning plus $5,342 and $1,823 to DBI, roughly $18,400 before trade permits and school fees; DBI says City fees typically run 6-9% of construction cost. Fees are waived for permits that legalize units built without permits before January 1, 2020) plus impact fees of None for a State-program ADU or JADU under 750 sq ft of gross floor area, and none of any size on a lot with 3 existing units or fewer (Planning Code 207.2(j)); a larger ADU on a lot with 4 or more units pays impact fees in proportion to the primary unit's gross floor area at the rates in the Impact Fee Register (indexed 2% on January 1, 2026). Section 207.1 contains no parallel exemption for Local-program ADUs; confirm with the Planning Division. SFPUC water and wastewater capacity charges apply only if a new or larger meter is needed (5/8-inch meter: $2,288 water, $6,006 wastewater, FY2025-26 rates); a single-family home adding one ADU usually needs no added water capacity. Quotes for the same scope commonly vary 20-40% between builders, so collect at least three bids.

Look for a licensed contractor with completed ADU projects in San Francisco specifically — ADUs involve local zoning, setback rules, and utility connections that general remodelers may not have handled. Verify the license, ask for an ADU-specific portfolio and references, confirm they carry liability and workers' comp insurance, and get a written fixed-price or detailed bid. Submit a request below and we'll forward it to local ADU builders serving San Francisco for free quotes.

Most full-service ADU builders manage the permit process for you. In San Francisco the approval process is "Both programs need a DBI building permit filed through the PermitSF portal with an ADU Screening Form (elect State/Hybrid or Local and sign the Rent Ordinance affidavit), a Permit Applicant and Authorized Agent form and the 60-day Tolling Declaration. State program (Planning Code 207.2): ministerial review, no CEQA, no Section 311 neighbor notice, no discretionary review, no appeal to the Board of Appeals (Ordinance 222-25), no design review except objective historic standards; a full-permit application is reviewed at a free virtual Permit Review Roundtable where DBI, Planning, Public Works, Fire and SFPUC deliver all comments in one meeting. Local program (207.1): at least 15 calendar days before applying, post a Notice of Addition of ADU and an owner's declaration in the building and mail them to every unit, file the declaration with the Rent Board (tenants have 30 days to object), then file a Project Application (PRJ) with Planning for in-house review and obtain a Planning Approval Letter before DBI will accept the building permit; Zoning Administrator waivers (207.1(g)) and, where the lot has rental units, a recorded Costa-Hawkins regulatory agreement. No Local-program ADU on a lot with an owner move-in eviction in the past 5 years or another no-fault eviction in the past 10 years (207.1(c)(2))" with a typical review timeline of 60 days from a complete application under Gov. Code 66317 (SB 543, January 2026: deemed approved if the City does not act). DBI requires every ADU applicant to sign an Application Processing Time Tolling Declaration choosing either to pause the 60-day clock while revising plans or to keep it running, in which case DBI may deny the application if code compliance is not shown within 60 days and revised plans are due at least 10 business days before the deadline. Local-program projects add the 15-day tenant notice, a 30-day Rent Board objection window (up to 90 days more if a tenant objects) and Planning in-house review before the building permit is filed; DBI states that State-program full permits generally have a shorter review and issuance timeline than the Local program. The City publishes no average issuance times. Confirm in writing whether permit fees, plan check (Electronic plan review in Bluebeam Revu with a required Back Check page. Plans must be stamped by a licensed design professional unless the home is wood-frame, under 2 stories plus basement, under 25 ft wide between bearing walls and under 25 ft tall (Information Sheet G-01). An ADU must be at least 220 sq ft with 7.5-ft ceilings in living and sleeping rooms, its own entrance, a rescue window in every bedroom and an exit path of no more than 125 ft to the street. Buildings with 3 or more units and a rear-yard sleeping room may need a fire alarm and ground-floor sprinklers; a fire flow study is required for new floor area, and street tree, Public Works right-of-way, Maher soil and construction-waste requirements can apply), and impact fees are included in the bid or billed separately.

Plan for the permit review (60 days from a complete application under Gov. Code 66317 (SB 543, January 2026: deemed approved if the City does not act). DBI requires every ADU applicant to sign an Application Processing Time Tolling Declaration choosing either to pause the 60-day clock while revising plans or to keep it running, in which case DBI may deny the application if code compliance is not shown within 60 days and revised plans are due at least 10 business days before the deadline. Local-program projects add the 15-day tenant notice, a 30-day Rent Board objection window (up to 90 days more if a tenant objects) and Planning in-house review before the building permit is filed; DBI states that State-program full permits generally have a shorter review and issuance timeline than the Local program. The City publishes no average issuance times in San Francisco) plus construction. Most detached ADUs take 4-8 months of construction after permits are issued; garage conversions and prefab units are often faster. Ask each builder for a realistic schedule and what could delay it.