Everything homeowners ask about building an ADU in San Antonio — answered with 2026 data.
Yes, ADUs are allowed in Permitted by right (subject to use-specific standards) in most single-family/residential and rural districts under the UDC in San Antonio, TX. The maximum size for a detached ADU is 800 sq ft (1,200 sq ft in the RE zone) per UDC §35-371. Attached ADUs can be up to Up to 35% of the principal dwelling's living area (UDC §35-371). San Antonio has an ADU-friendliness score of 5/10. Check our full San Antonio ADU rules page for complete zoning details.
ADU construction in San Antonio typically costs $110,000-$220,000. The cost per square foot averages $140-$275. Garage conversions are more affordable at $50,000-$130,000, while prefab ADUs cost $75,000-$170,000. Permit fees add $4,000-$6,500 to your budget. See our detailed San Antonio ADU cost guide.
Detached ADUs in San Antonio can be up to 800 sq ft (1,200 sq ft in the RE zone) per UDC §35-371. Attached ADUs are limited to Up to 35% of the principal dwelling's living area (UDC §35-371). Junior ADUs (JADUs) have a cap of Not allowed. Maximum height is Generally may not exceed the height of the primary residence (commonly 25-30 ft); varies by zoning district. You are allowed up to 1 ADU per lot on a qualifying lot.
Rear setback: 5 feet (detached ADU may be 3 ft or more from side and rear lines per UDC §35-371). Side setback: 5 feet. Front setback: 25 feet. Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
One on-site space required only if the ADU exceeds 800 sq ft of gross floor area; no parking required for smaller units. Many cities and states have been relaxing ADU parking requirements in recent years. In California, no additional parking is required for ADUs near transit.
Required — owner must occupy either the principal unit or the ADU as their permanent residence (residency affidavit required); the owner-occupied unit may not be rented. 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 Antonio is typically 90-120 days. Plan check: 4-6 weeks. Pre-approved plans availability: Not available.
Average ADU rental income in San Antonio: 1-bedroom units rent for $1,050-$1,550/month, 2-bedroom units for $1,300-$1,950/month. Short-term rentals: Not permitted. Expected ROI: 5-7% annual return.
The minimum lot size for an ADU in San Antonio is No ADU-specific minimum (UDC 35-371 / Information Bulletin 402 set none). 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 Antonio, a garage conversion typically costs $50,000-$130,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.