ADU (Accessory Dwelling Unit) permit in San Antonio, TX
Yes — you need a permit for adu (accessory dwelling unit) work in San Antonio.
Building an accessory dwelling unit (garage apartment, casita) creates a new habitable dwelling unit - a building permit is required and the ADU must comply with the zoning use regulations for accessory dwellings. It is not an exempt accessory structure (the 300 sq ft shed exemption is for tool/storage sheds, not dwellings). Occupancy of the ADU is tied to owner-occupancy of the ADU or the principal dwelling.
| Permit needed? | Yes |
|---|---|
| Where the line falls | Building an accessory dwelling unit (garage apartment, ca… |
| Fee | New residential construction fee schedule (Sec. 10-39) and city fee schedule (Sec. 10-10); no dollar figures in the code. |
| Review time | Not in the ordinance |
| Code section | Sec. 35-371 Accessory Dwellings; building permit under Sec. 10-6 |
| Based on | IRC 2024 as amended by the city (Sec. 10-36); UDC zoning Sec. 35-371 |
How to pull the permit
- Put together a site plan showing where the work goes, with dimensions.
- Apply through the San Antonio building department.
- Pay the permit fee when the permit is issued. Work done before that isn't covered.
- Book each inspection listed on the permit as the job reaches that stage.
Either of you can pull it. When a contractor does the work, it is normally their job.
If you skip it
Starting the work before the permit is issued makes the permit fee double (Sec. 10-10(d)).
Nearby cities, same job
Rules stop at the city line. If your lot is near a boundary, or you work across several towns, this is where they differ.
| City | Distance | Permit? | Where the line falls |
|---|---|---|---|
| San Antonio | — | Yes | Building an accessory dwelling unit (garage apartment, ca… |
| New Braunfels | 30 mi | Yes | No size threshold in the code |
| Austin | 74 mi | Yes | No size threshold in the code |
| Round Rock | 90 mi | Yes | No size threshold in the code |
| Killeen | 121 mi | Yes | You need a building permit to build an accessory dwelling… |
| College Station | 154 mi | Yes | No size threshold in the code |
Other work in San Antonio
Questions people ask
How much does a adu (accessory dwelling unit) permit cost in San Antonio?
New residential construction fee schedule (Sec. 10-39) and city fee schedule (Sec. 10-10); no dollar figures in the code.. Valuation-based fees mean the number depends on what the job is worth, so the department quotes it when you apply.
I already built it without a permit. What now?
San Antonio can issue a stop-work order and require you to apply after the fact, sometimes with an extra fee. Work that was covered up may have to be opened for inspection. Full walkthrough here.
Does unpermitted work cause problems when selling the house?
Often, yes. A buyer's inspector or the title company may flag it, and lenders can balk at financing a home with open or missing permits. What to do about it.