Everything homeowners ask about building an ADU in San Jose — answered with 2026 data.
Yes, ADUs are allowed in All residential zones (R-1, R-2, R-M, R-MH) in San Jose, 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 Jose has an ADU-friendliness score of 8/10. Check our full San Jose ADU rules page for complete zoning details.
ADU construction in San Jose typically costs $180,000-$400,000. The cost per square foot averages $250-$450. Garage conversions are more affordable at $100,000-$220,000, while prefab ADUs cost $130,000-$300,000. Permit fees add $4,000-$14,000 to your budget. See our detailed San Jose ADU cost guide.
Detached ADUs in San Jose 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 for detached. You are allowed up to 1 ADU + 1 JADU 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 Jose is typically 60 days. The plan check process takes approximately Standard review process. Pre-approved plans availability: Limited pre-approved options available.
Average ADU rental income in San Jose: 1-bedroom units rent for $2,000-$2,800/mo/month, 2-bedroom units for $2,500-$3,500/mo/month. Short-term rentals: Restricted; requires transient occupancy tax registration. Expected ROI: 5-9% annual return.
The minimum lot size for an ADU in San Jose is No minimum. 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 Jose, a garage conversion typically costs $100,000-$220,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.