How Much Does an ADU Cost in San Francisco, CA?

Construction Cost Breakdown

Building an ADU in San Francisco costs between $200,000-$450,000 for new construction, with per-square-foot costs averaging $300-$500. These figures include design, permitting, site preparation, and construction. The most affordable option is a garage conversion at $120,000-$250,000, while prefab/modular ADUs fall in between at $150,000-$350,000.

Permit Costs & Timeline

Permit fees in San Francisco are Replace the guessed range with SF's own published figures. DBI's own estimate: 'City fees range from 6-9% of construction costs' (and architects/engineers about 10%; at least $125,000 in material and labor for a new unit). PLANNING development application fee (Fee Schedule eff. 8/29/2025, rev. 6/15/2026) — New Construction: $3,502 flat under $100k; $3,504 base + 3.855% of cost above $100,000 in the $100k-499,999 band; $19,226 + 1.230% above $500,000. Alteration/Change of Use (garage or interior conversion): $504 under $10k; $516 + 5.274% above $10,000; $3,838 + 3.524% above $50,000; $5,638 + 3.855% above $100,000. Neighborhood notification $121 + $4.25/envelope; permit-revision back check $366. DBI building permit fees are TWO separate charges under SF Building Code Table 1A-A (amended Ord. 112-26, eff. 7/12/2026) — Plan Review: $1,671 + $15.60 per $1,000 over $50,000 ($50k-200k band), $4,011 + $13.31 per $1,000 over $200,000 ($200k-500k band); Permit Issuance: $677 + $4.83 per $1,000 ($50k-200k), $1,402 + $4.21 per $1,000 ($200k-500k). Table 1A-A note 1 states these exclude Public Works, Planning, Fire, Public Health and plumbing/electrical/mechanical permit fees. Add SFUSD school facility fees (calculated by DBI staff), SFPUC and Public Works right-of-way permits. OUR WORKED EXAMPLE (label as our calculation, not a published number): a $300,000 detached ADU = Planning $11,214 + DBI plan review $5,342 + DBI issuance $1,823, roughly $18,400 before trade permits and school fees — about 6% of construction cost, consistent with DBI's 6-9%. FEE WAIVER: building permit fees are waived for permits granting legal status to dwelling units built without permits, for activities prior to 1/1/2020 (Board Ord. 150571).. The review timeline is 60 days from a COMPLETE application under Gov. Code 66317 — but SF requires every ADU applicant to sign an 'Application Processing Time Tolling Declaration Form' electing either to TOLL (pause) the 60-day clock while revising plans, or to hold the City to it. If the applicant declines tolling, DBI may DENY the application if code compliance cannot be established within 60 days, and revised plans must be resubmitted at least 10 business days before the period ends. Most applicants therefore toll and the real elapsed time exceeds 60 days. Add the Local-Program pre-clock: 15 calendar days of posted notice before filing, a Rent Board declaration with a 30-day tenant petition window (Rent Board targets transmitting a determination within 90 calendar days of a petition), then Planning In-House Review and a Planning Approval Letter — all before the building permit is filed. SF states State-Program full permits 'generally has a shorter review and issuance timeline than the Local program.', with plan check: Expedited plan check available. Impact fees are MORE GENEROUS THAN STATE LAW — commercially the second-biggest correction. PC 207.2(j) waives impact fees for a State-Program ADU or JADU that is under 750 sq ft of Gross Floor Area, OR that is proposed on a lot with THREE EXISTING UNITS OR FEWER regardless of size. So on a typical SF single-family, duplex or triplex lot, a State-Program ADU pays NO impact fees even at 1,000 sq ft. Above those thresholds, fees are imposed proportionately to the gross floor area of the primary dwelling unit. CAVEAT TO FLAG: the Planning Code says 'Gross Floor Area' for the 750 threshold while Planning Director Bulletin No. 3 says 'interior livable space' — the code controls. SECOND CAVEAT: 207.2(j) is expressly limited to the State Program; PC 207.1 contains no parallel exemption, so Local-Program impact fees are unresolved.. Pre-approved plans: MISLEADING AS WRITTEN — rewrite. DBI runs a Pre-approved ADU Plans program, but it is a program for BUILDING DESIGNERS to submit designs for pre-approval, not a homeowner catalogue. Verified terms: a $2,408 flat fee per plan submitted for pre-approval (a widely repeated $1,519 figure is stale); plans 'should be designed for 25 ft lots'; pre-approval 'is only valid during the current code cycle'; pre-approved plans CANNOT be used in slope protection areas, landslide and liquefaction zones, Maher Zones or flood zones; and site-specific plan check is still required (Planning Code compliance, soils report and site survey, fire separation distance, foundation design, SFUSD fees, tree removal, drainage). Submissions go to dbi.preapprequests@sfgov.org and DBI schedules a Permit Review Roundtable. Do NOT claim it 'saves 2-3 months on design' — nothing on the city's pages supports a time saving. I found NO published catalogue of pre-approved plans; SF Planning's ADU page, Planning Director Bulletin No. 3 and the Local ADU Program Chart do not mention the program at all..

Rental Income & ROI

A typical ADU in San Francisco generates approximately $32,400 per year in rental income based on average 1-bedroom rents. At an average construction cost of $325,000, the estimated payback period is 10.0 years — before accounting for the resale value the ADU adds, which an appraiser determines from comparable sales in San Francisco and varies by market (often less than build cost).

Ways to Reduce ADU Costs in San Francisco