A garage conversion rebuilds an attached or detached garage as a self-contained dwelling. In San Antonio it counts as an ADU, so the same size cap, owner-occupancy affidavit and permit steps apply as for a new unit. As of October 2026, one published local guide puts conversions and attached units at about $40,000 to $80,000 to build.
Which garages convert well?
Ones with a level, intact slab, straight framing, a sound roof and enough ceiling height for a habitable room. Older detached garages behind homes in the city's established neighborhoods can be good candidates; garages with cracked slabs or sagging roofs often cost nearly as much to fix as to replace.
What work is typical?
- Filling the overhead door opening with an insulated wall, window or entry.
- Trenching the slab for kitchen and bathroom drains.
- Insulating walls and ceiling, and adding a right-sized HVAC system backed by Manual J and Manual S calculations, which the city asks for.
- Upgrading electrical service if the panel cannot carry the new load.
- Adding egress windows and smoke and carbon monoxide alarms.
Do I lose required parking?
San Antonio's ADU page requires a dedicated off-street space only for ADUs over 800 sq ft. Most one- and two-car garages convert to units under that size. Your HOA or deed restrictions may still require garage parking; check before you commit. See deed restrictions and HOAs.
Is an attached garage different?
The interior work is similar. An attached conversion follows the house's zoning height limits and needs a fire-rated separation from the main home if the two are separate dwellings.