Everything homeowners ask about building an ADU in San Antonio — answered with 2026 data.
Yes, ADUs are allowed in Permitted by right in R-1, R-2, R-3, R-4, R-5, R-6, RM-4, RM-5 and RM-6, and in multi-family districts on lots with up to five units in total (UDC 35-371; DSD ADU page, 2026). A lot whose owner will not live on site must instead be rezoned to a district that allows more than one dwelling. Check your district on the city's OneStop map; recorded deed restrictions and HOA rules still apply. in San Antonio, TX. The maximum size for a detached ADU is The larger of 800 sq ft gross floor area or 50% of the main house's gross floor area, capped at 1,600 sq ft (UDC 35-371; IB 402 FAQ 1). Every lot may therefore have an ADU of at least 800 sq ft regardless of the size of the main house. Attached ADUs can be up to Same formula as a detached unit: the larger of 800 sq ft or 50% of the main house's gross floor area, up to 1,600 sq ft. San Antonio has an ADU-friendliness score of 7/10. Check our full San Antonio ADU rules page for complete zoning details.
ADU construction in San Antonio typically costs $125,000-$320,000. The cost per square foot averages $225-$400. Garage conversions are more affordable at $30,000-$90,000, while prefab ADUs cost $150,000-$300,000. Permit fees add FY2026 DSD fee schedule (rev. Oct 2025), new residential construction by size: $988 total basic permit fees for 501-1,000 sq ft, $1,022 for 1,001-1,250 and $1,201 for 1,251-1,500 sq ft (building, trade and sewer permits plus a $200 plan review). 100% waivable for income-qualified ADUs. to your budget. See our detailed San Antonio ADU cost guide.
Detached ADUs in San Antonio can be up to The larger of 800 sq ft gross floor area or 50% of the main house's gross floor area, capped at 1,600 sq ft. Attached ADUs are limited to Same formula as a detached unit: the larger of 800 sq ft or 50% of the main house's gross floor area, up to 1,600 sq ft. Junior ADUs (JADUs) have a cap of No junior ADU category in the San Antonio UDC; a unit carved out of, or added onto, the house is simply an attached ADU under UDC 35-371 and uses the same size rule. Maximum height is Detached ADU: 2 stories and 25 ft maximum (IB 402 FAQ 4; DSD ADU page). Attached ADU: the height limit of the underlying zoning district. You are allowed up to One ADU per lot on a qualifying lot.
Rear setback: 5 ft standard for a detached ADU; may be reduced to 3 ft if the structure has no eave overhang within 3 ft of the line, and walls within 5 ft of the line must be fire-rated under the IRC (IB 402 FAQ 2; DSD ADU page). The ADU must be located in the rear of the lot (IB 402 FAQ 4). Side setback: 5 ft standard for a detached ADU; 3 ft allowed with no eave overhang and IRC fire rating within 5 ft of the line (IB 402 FAQ 2). An attached ADU keeps the main house's district side setback. Front setback: No ADU-specific front setback: the unit must sit in the rear of the lot (IB 402 FAQ 4), so the main house's district front setback governs. Confirm your district's setback table with DSD Zoning (210-207-1111). Note that garage conversions may be exempt from setback requirements if the existing structure is already within the setback area.
None required for an ADU of 800 sq ft or less. An ADU over 800 sq ft gross floor area needs one dedicated off-street parking space (IB 402 FAQ 4; DSD ADU page). 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. The owner must occupy either the main house or the ADU as a permanent residence, sign a notarized affidavit, and record a covenant with the Bexar County Clerk before the permit issues; the owner-occupied unit may never be rented (UDC 35-371(a)(1); IB 402 Attachment B). Enforcement uses voter registration, homestead and driver's-license records and cross-checks against STR permits. 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 DSD publishes only its review targets: up to 3 business days for intake/completeness review and up to 3 business days for the first plan-review redlines; the permit issues once corrections are accepted and fees paid (DSD ADU page; DSD fact sheet 3/28/2023). Total time to permit is not published. Plan check: Up to 3 business days to first redline comments (DSD ADU page). Pre-approved plans availability: Yes: 5 Casita Permit-Ready Plans (375, 490, 675, 794 and 800 sq ft), reviewed and approved by DSD as complete building plans; $450 base fee paid to the designer, site-specific changes priced separately; owners at or below 80% AMI can get up to $4,500 design-fee reimbursement.
Average ADU rental income in San Antonio: 1-bedroom units rent for $950-$1,250/month, 2-bedroom units for $1,200-$1,500/month. Short-term rentals: Only with a City STR permit (UDC 35-374.01): Type 1 owner-occupied lot, $300 application, 3-year term, one permit per unit, blockface density caps. Expected ROI: 4-8% gross rent yield.
The minimum lot size for an ADU in San Antonio is No ADU-specific minimum lot size in UDC 35-371, IB 402 or the DSD ADU page; the district's lot standards for the main house apply. Confirm with DSD Zoning. 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 $30,000-$90,000. The key advantages are lower cost (no foundation work), potential setback exemptions, and faster permitting. Read our complete garage conversion guide.
Tell us about your project and we'll pass it to ADU builders serving San Antonio. Free, no obligation — you choose who to work with. We don't have builders in every area yet; if nobody covers yours, we'll email you to say so.
🔒 Your info is secure. We share it only with contractors quoting your project. No spam, no obligation.
Just browsing? Search ADU builders near you by ZIP code.