A garage conversion is the cheapest square footage you can add to a San Antonio house, because the slab, the walls, and the roof are already paid for. What you are buying is everything that makes a garage a room: insulation, drywall, a real floor, windows, electrical that meets code, and a way to heat and cool it. What you are giving up is the garage, and in a neighborhood with covenants or a tight driveway that is worth thinking about before the first quote.
Here is what conversions cost, what pushes one from a simple bedroom to a full apartment, and what the City of San Antonio requires before you start.
Garage Conversion Cost Breakdown
What these ranges price: converting an existing attached garage into conditioned living space within its footprint: insulation, drywall, flooring, electrical, HVAC tie-in. A kitchen or a separate apartment (ADU) costs more, covered below.
| Level | Price Range (per conversion) |
|---|---|
| Basic (insulate, drywall, floor, lighting) | $4,000 – $12,000 |
| Mid-range (bedroom or office, HVAC extended, windows) | $12,000 – $25,000 |
| High-end (adds a bathroom, upgraded finishes) | $25,000 – $52,000 |
These are national ranges, last reviewed September 2026, from This Old House's June 2026 garage conversion guide (basic $4,000 to $12,000, mid-range $12,000 to $25,000, high-end $25,000 to $40,000, luxury $40,000 to $52,000 and up, with an average project around $30,700). They are not a study of the San Antonio market. 365 Builders works statewide, and labor and material costs move between cities. Treat them as a starting point, not a quote.
The same guide prices conversions by what the room becomes, which is often the more useful way to think about it:
- Home office: about $8,200 to $14,700
- Bedroom: about $10,400 to $17,800
- Studio apartment or ADU with a bathroom and kitchen: about $31,500 to $73,200
That last line is the one that surprises people. Adding a kitchen and a bathroom means running new water, drain, and vent lines, usually through or under a slab, plus a second panel or subpanel. It is a different project, and in San Antonio it is also a different permit path.
What Drives the Price Up or Down
1. The garage door wall
Every conversion has to do something with the opening. The cheapest answer is to frame it in and side it to match; the nicest is a window wall or French doors. Either way, the new wall needs a footing check, insulation, and a finish that does not look like a filled-in garage from the street. This is where the curb appeal of the whole project is decided.
2. The floor
Garage slabs slope toward the door and sit a step below the house. Leveling with a self-leveling compound or a sleeper floor, then insulating and finishing, is a bigger line than most people budget. Skipping the slope correction shows up as a rolling chair and a floor that never feels right.
3. Heating and cooling
A garage has no ductwork. Extending the existing system works if the unit has the capacity, and a load calculation will tell you. If it does not, a ductless mini-split is the usual answer and runs a few thousand dollars installed. This Old House puts the HVAC line at $300 to $5,000 depending on which way you go.
4. Plumbing
None for an office or bedroom. A half bath adds a few thousand ($1,500 to $4,000 in the June 2026 guide). A full bath with a shower, or a kitchen, moves you into the ADU band and into slab work.
5. Electrical
Most garages have one or two circuits and a bare-bulb fixture. A bedroom needs outlets on every wall, a smoke detector tied to the house, lighting, and often a dedicated circuit for the mini-split. Get the electrical priced as its own line, and expect it to go up if the room needs a subpanel.
Permits in San Antonio: What the City Actually Requires
This is the part most online cost guides get vague about, so here it is from the city's own form. San Antonio Development Services lists garage conversion as a permitted residential repair on its Residential Repair Permit Application (revised October 2025), defined as "converting an existing, attached garage to livable space within existing footprint," and it requires a site plan. A framing inspection is required, and a final inspection closes it out.
Two things on that same application move a conversion off the simpler form and into full plan review:
- Two or more exterior walls repaired, modified, or replaced.
- A detached accessory dwelling, which the city treats as an ADU with its own review.
Those two are what the form itself names. Size, a second story, and anything structural beyond the framing are the plans examiner's call, so ask Development Services which path your specific project takes before you price the permit.
The application states the fee as permit base plus surcharge plus processing charge, without a dollar figure, so ask the city or your contractor for the current number rather than trusting a blog. And if the house is in a neighborhood with an HOA, check the covenants before you check with the city; plenty of San Antonio subdivisions restrict converting the garage or require a replacement covered parking space.
An unpermitted conversion is not a savings. It comes up at resale. What unpermitted space means for your coverage and your appraised value is a question for your insurer and a local appraiser or agent — ask them before you decide to skip the permit, not after.
Decide These Before You Get Quotes
- What the room is for. Office, bedroom, rental, in-law suite. This sets the plumbing, the electrical, and whether you are in the ADU band.
- Whether you can live without the garage. Where does the car go, and where does everything that is in the garage now go? A shed or a carport is often part of the real cost.
- How the front will look. Get a drawing or at least a photo of a conversion the contractor has done. The garage-door wall is the whole street view of the project.
- Heating and cooling plan. Extend or mini-split. Ask the contractor for the load calculation, not a guess.
- The permit path. Ask the contractor which form they will file and whether your project needs plan review. If they cannot answer, they have not done many of these in San Antonio.
Frequently Asked Questions
How long does a garage conversion take?
It depends on scope and on the city. A basic office or bedroom with no plumbing is a few weeks of work once the permit is in hand; a bathroom or an ADU takes considerably longer and adds plan-review time up front. We put a schedule in writing with the estimate and tell you which parts wait on the city.
Will a garage conversion add value to my home?
Finished, permitted, conditioned square footage is what an appraiser has to work with; unpermitted space is treated differently, and how differently is the appraiser's judgment, not a rule we can publish. Whether the room adds more than it costs also depends on the neighborhood and on whether buyers there want a garage more than a fourth bedroom. Ask a local agent and, if resale is the reason for the project, an appraiser, before you commit.
Can I convert a detached garage?
Yes, but the city treats a detached garage converted to living space as an accessory dwelling, which means plan review rather than the repair permit. The conversion itself costs about the same; the paperwork and timeline are longer.
Do I need to add a window?
A bedroom needs an egress window or door that meets code for size and sill height, and every habitable room needs natural light and ventilation. Plan on at least one real window in the garage-door wall or a side wall.
Get a Free Garage Conversion Estimate in San Antonio, TX
At 365 Builders, we provide detailed, transparent estimates for residential projects throughout San Antonio, TX and across Texas. We've been serving the community since 2015, and we stand behind our work. Tell us what you want the room to be and send a photo of the garage from the street, and we will tell you which band you are in and which permit path applies before we build a number.
Explore our residential construction services, see what we do in San Antonio, read our San Antonio home remodel guide, or browse all the areas we serve across Texas.
Call us at (956) 607-0470 or request a free quote to get started.