Everything homeowners ask about building an ADU in San Diego — answered with 2026 data.
Yes, ADUs are allowed in All residential zones; also allowed in some commercial mixed-use zones in San Diego, CA. The maximum size for a detached ADU is 1,200 sq ft. Attached ADUs can be up to 1,200 sq ft or 50% of primary dwelling. San Diego has an ADU-friendliness score of 9/10. Check our full San Diego ADU rules page for complete zoning details.
ADU construction in San Diego typically costs $120,000-$300,000. The cost per square foot averages $180-$350. Garage conversions are more affordable at $70,000-$160,000, while prefab ADUs cost $90,000-$220,000. Permit fees add $3,500-$12,000 to your budget. See our detailed San Diego ADU cost guide.
Detached ADUs in San Diego can be up to 1,200 sq ft. Attached ADUs are limited to 1,200 sq ft or 50% of primary dwelling. Junior ADUs (JADUs) have a cap of 500 sq ft. Maximum height is 25 ft (2 stories). You are allowed up to 1 ADU + 1 JADU per single-family lot; up to 8 on multifamily on a qualifying lot.
Rear setback: 4 ft. Side setback: 4 ft. Front setback: Per underlying zone. 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 Diego is typically 60 days (often faster). The plan check process takes approximately Standard plan check included. Pre-approved plans availability: Yes — companion unit program with pre-approved designs.
Average ADU rental income in San Diego: 1-bedroom units rent for $1,600-$2,200/mo/month, 2-bedroom units for $2,000-$2,800/mo/month. Short-term rentals: Allowed with STRO license in certain zones. Expected ROI: 7-11% annual return.
The minimum lot size for an ADU in San Diego is No minimum lot size for JADUs. 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 Diego, a garage conversion typically costs $70,000-$160,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.