Everything homeowners ask about building an ADU in San Francisco — answered with 2026 data.
Yes, ADUs are allowed in RH-1, RH-2, RH-3, RM, RTO zones and most residential districts in San Francisco, CA. The maximum size for a detached ADU is 1,200 sq ft (state minimum; local program caps at 850-1,000 sq ft). Attached ADUs can be up to 1,000 sq ft or 50% of primary dwelling. San Francisco has an ADU-friendliness score of 9/10. Check our full San Francisco ADU rules page for complete zoning details.
ADU construction in San Francisco typically costs $200,000-$450,000. The cost per square foot averages $300-$500. Garage conversions are more affordable at $120,000-$250,000, while prefab ADUs cost $150,000-$350,000. Permit fees add $5,000-$20,000 depending on scope to your budget. See our detailed San Francisco ADU cost guide.
Detached ADUs in San Francisco can be up to 1,200 sq ft (state minimum; local program caps at 850-1,000 sq ft). Attached ADUs are limited to 1,000 sq ft or 50% of primary dwelling. Junior ADUs (JADUs) have a cap of 500 sq ft. Maximum height is 25 ft for detached ADUs. You are allowed up to 1 ADU + 1 JADU per lot on a qualifying lot.
Rear setback: 4 ft minimum. Side setback: 4 ft minimum. Front setback: Must meet zone's front setback requirement. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
No parking required. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Not required. Note that owner-occupancy rules vary by state law — California and several other states have eliminated this requirement for standard ADUs.
The ADU permit review timeline in San Francisco is typically 60-day review period (state-mandated). The plan check process takes approximately Expedited plan check available. Pre-approved plans availability: Yes — SF has pre-approved ADU plan sets.
Average ADU rental income in San Francisco: 1-bedroom units rent for $2,200-$3,200/mo/month, 2-bedroom units for $2,800-$4,000/mo/month. Short-term rentals: Heavily regulated; 90-day annual cap for unhosted. Expected ROI: 5-8% annual return.
The minimum lot size for an ADU in San Francisco is No minimum lot size. This applies to detached ADUs — garage conversions and JADUs may have different or no lot size requirements.
Garage conversions are one of the most popular and affordable ADU options. In San Francisco, a garage conversion typically costs $120,000-$250,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.