A garage conversion is usually the lowest-cost path to an ADU in San Antonio — $30,000-$90,000, versus $125,000-$320,000 for a new detached build — because the shell already exists.
Garage Conversion Cost in San Antonio
Converting an existing garage in San Antonio runs $30,000-$90,000. That's well under the $125,000-$320,000 typical cost of a ground-up detached ADU, because you're reusing the foundation, walls, and roof. The biggest variables are whether the slab and framing are sound, what utility/electrical upgrades are needed, and your finish level. 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.. A converted unit rents for about $950-$1,250/mo (1BR) in San Antonio.
The San Antonio Garage Conversion Permit Process
A garage-to-ADU conversion in San Antonio needs building permits even if the exterior is unchanged. Approval process: By right, no zoning hearing: file a Residential Building Permit in BuildSA (a combination permit covering building, electrical, mechanical and plumbing) with a site plan, foundation plan, IECC energy report and Manual J/S HVAC sizing, plus proof that the owner-occupancy affidavit and covenant are recorded with Bexar County (IB 402; DSD ADU page). One of the five city Casita Permit-Ready Plans can serve as the building plans. The review timeline is 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., with plan check: Up to 3 business days to first redline comments (DSD ADU page). Pre-approved plans: 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.
- Confirm eligibility — 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..
- Prepare conversion plans — layout, egress windows, insulation, ventilation, smoke/CO detectors, plus a kitchen and bathroom.
- Submit for plan check — Up to 3 business days to first redline comments (DSD ADU page).
- Pull permits and build — fees run 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.; then framing, electrical, plumbing, and final inspection.
Parking Rules for a Garage Conversion
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). Garage conversions sometimes trigger different parking rules than new detached ADUs, so confirm replacement-parking requirements with San Antonio before you start. Note: 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.
The JADU Option for an Attached Garage
If your garage is attached to the house, you can convert it into a junior ADU (JADU) — capped at 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. and built within the existing walls. JADUs are cheaper and faster to permit than a full ADU, though they may share sanitation with the main home. A full ADU gives you more size and a separate unit; a JADU is the budget route.
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San Antonio Garage Conversion FAQ
How much does a garage conversion cost in San Antonio?
Do I need a permit to convert a garage in San Antonio?
Do I have to replace the parking if I convert my garage in San Antonio?
How long does a garage conversion take in San Antonio?
Can I convert an attached garage into a JADU in San Antonio?
Compare your options: see the full San Antonio ADU rules, estimate your build with the San Antonio ADU cost calculator, or read the general garage conversion guide.