What is a garage conversion ADU?
It turns an existing garage into a complete dwelling: insulated walls, a kitchen, a bathroom, its own entrance and its own cooling. The garage door opening becomes wall, windows or a door.
Is converting a garage allowed in Houston?
Inside city limits, the city's second-unit rules apply to the new living space, and your deed restrictions decide whether a second residence is permitted at all. In the suburbs it depends on the city. Richer detail is on each area page.
What happens to my parking?
Houston planning materials, as of October 2026, link second-unit parking to size: a unit of 1,000 sq ft or less may need no added space when certain criteria are met. Most garage conversions fall under that size. The main house still needs to meet its own parking requirement, so losing the garage can matter. We check both before design.
What work does a garage usually need?
- A slab check, since many garage floors slope toward the door and sit close to grade.
- Raising the floor where the lot is in the 500-year floodplain and the work counts as a substantial improvement.
- Insulation, a vapor strategy and air sealing for a humid climate.
- New window and door openings, with headers where the structure needs them.
- Plumbing for a kitchen and bathroom, including a sewer line to the garage.
- A load check on the electrical panel and a dedicated cooling system.
When does a garage conversion not pay off?
It depends on the garage. Termite damage, a cracked or low slab, or framing that cannot take new openings can cost nearly as much to fix as a rebuild. If the lot is in the floodplain, raising the floor inside an old shell is awkward. We inspect first and price the conversion against a rebuild with an apartment above.
How much does a garage conversion cost in Houston?
As of October 2026, one 2026 Houston market guide estimates about $60,000 to $110,000 for a 400 to 600 sq ft conversion. Angi's national range runs about $58,000 to $173,000. See the Houston ADU cost guide.
Related
As of October 2026. Sources: City of Houston Planning & Development (Livable Places); Houston Chapter 19 floodplain ordinance (2018 amendments); Harbert Group, Houston ADU guide (2026); Angi garage-to-ADU cost guide.
Check what your lot allows
Send your address and a photo of the garage if you have one. We check the structure, restrictions and flood zone first.