ADU Rules in San Francisco, CA (2026)

San Francisco, CA permits accessory dwelling units (ADUs) on residential properties. ADUs — also called granny flats, in-law units, backyard cottages, or secondary suites — are secondary housing units on a single-family or multifamily lot. California state law actively preempts local restrictions, making ADU approval a streamlined ministerial process. In San Francisco, the San Francisco Department of Building Inspection (DBI) handles ADU permit applications. Below you will find the current size limits, setbacks, fees, and timeline for building an ADU in San Francisco.

ADU Size Limits

ADU Size Limits in San Francisco: Detached ADU: up to 1000 sq ft (max height: 16 feet). Attached ADU: 50% of primary dwelling or 850 to 1,000 square feet, whichever is greater. Junior ADU (JADU): up to 500 sq ft — must be within the existing primary dwelling or accessory structure. The Gross Floor Area of a detached ADU that provides more than one bedroom shall not exceed 1,000 square feet.

Permit Fees

ADU Permit Fees in San Francisco: Plan check fee: Varies — typically $800–$3,500 for standard ADU based on project valuation. Building permit fee: Varies by valuation — typically $2,000–$6,000. Impact fees: None. School fees: Exempt for ADUs under 750 sqft per California ADU fee exemption (§§66314–66333 framework; school fee exemption codified in Health and Safety Code). ADUs 750+ sqft subject to school developer fees.. Total estimated permit cost: $3,000–$10,000 total permit fees depending on size and scope. Impact fees waived for ADUs under 750 sqft per California ADU framework (§§66314–66333; school/impact fee exemptions codified in H&S Code). Fee schedule: https://sfdbi.org/permits/permit-fees. SF DBI permit fee calculator available online.

Permit Timeline

San Francisco ADU Permit Timeline: The permitting agency shall either approve or deny the application to create or serve an accessory dwelling unit within 60 days from the date the permitting agency receives a completed application if there is an existing single-family or multifamily dwelling on the lot. Note: SF DBI typically processes ADU permits in 2-6 weeks for plan check; SF Planning pre-approval may add time if design review is triggered (operational, not codified). Apply through the San Francisco Department of Building Inspection (DBI) online permit portal. Phone: (415) 558-6088.

Setback Requirements

ADU Setback Requirements in San Francisco: Front setback: Same as zone standard. Side setback: 4 feet. Rear setback: 4 feet. State law requires 4-foot side and rear setbacks for new detached ADUs per Gov Code §66314(d)(7). No setback required for ADU replacing existing structure in same footprint. Front setback follows Planning Code zone standards. SF Planning Code Section 207.1.

Parking Requirements

Parking Requirements: No additional parking required for ADUs within one-half mile of public transit (BART, Muni Metro, major bus lines). SF is characteristically transit-rich — parking waivers are available throughout much of the city per California Gov Code §66322(a)(1) and SF Planning Code Section 207.1. Note: the 'entirely transit-rich' characterization is an editorial interpretation; the statutory mandate applies wherever a unit is within one-half mile of public transit per §66322(a)(1).

Restrictions & Requirements

• •ADU must comply with objective Planning Code standards
• •ADU cannot be sold separately from primary dwelling (except under Urban Lot Split per Gov Code §66411.7)
• •Short-term rental of ADU requires primary resident to be on-site during rental
• •ADU must have permanent foundation
• •In-law units in RH-1 zones must meet residential habitability standards
• •Hillside areas may have additional structural review requirements

How Many ADUs Are Allowed?

Number of ADUs Allowed in San Francisco: Single-family lots: 1 ADU + 1 JADU per single-family lot (RH-1, RH-2 zones). Multifamily properties: Up to 25% of existing units (minimum 2) as detached ADUs; 1 ADU per existing unit for internal conversions per Gov Code §66323(a)(3). Per Gov Code §66323(a)(3): multifamily properties may convert up to 25% of existing units to ADUs. Urban Lot Split (Gov Code §66411.7) may allow additional units on qualifying RH-1 parcels.

State Law & Preemption

Historic District Considerations

Frequently Asked Questions