Garage Conversions and ADUs in San Antonio: What the City's Rules Say

A garage conversion in San Antonio and a backyard ADU both add living space without a full addition, but the City treats them differently. Settle which one you are building, and what the City's rules allow on your lot, before anyone draws plans. Everything below reflects City of San Antonio Development Services Department (DSD) pages and information bulletins as of October 2026. Other cities around San Antonio set their own rules, so if your home sits in one of the separate cities in our San Antonio remodeling service areas, check with that city's permit office first.

Garage conversion in San Antonio or an ADU?

The line can blur. The City's Casita Program describes casitas, another name for ADUs, as either attached, such as a garage apartment, or detached. A converted garage with its own kitchen and entrance may be reviewed as an attached ADU rather than extra rooms for the main house. Ask DSD which category your plan falls into before design starts, because the permit path changes:

• A conversion that stays part of the house is permitted as a remodel. On a hired-contractor conversion, DSD's Getting Started page says licensed trades request the trade permits and inspections. For plumbing only, DSD also permits a resident owner to obtain a permit for an existing homestead. The homeowner affidavit requires personal work without assistance, excludes business or rental property and requires City inspection.
• An ADU goes through DSD's Residential Building Permit Application. DSD's IB 402 on accessory dwelling units says these are combination permits that include the required mechanical, plumbing and electrical inspections, so stand-alone trade permits should not be pulled separately. Every ADU has to comply with the International Residential Code.

What the City's ADU page says (as of October 2026)

The City of San Antonio's Development Services Department (DSD) publishes its current ADU permit rules. As of October 2026, that page says:

• Zoning: ADUs are allowed in R-1 through R-6 and RM-4 through RM-6 districts, and in multi-family districts up to a total of five units.
• How many: one ADU per property.
• Size: up to 800 square feet or half the size of the main house, whichever is larger, with a cap of 1,600 square feet. Every eligible property can have at least 800 square feet, and the size rule applies to attached and detached ADUs.
• Bedrooms: no limit on the number of bedrooms.
• Owner occupancy: the owner must live in the main house or the ADU. If the owner does not live on site, the property must be rezoned.
• Parking: only ADUs over 800 square feet need a dedicated off-street parking space.
• Setbacks: a detached ADU can sit 3 feet or more from side and rear property lines, but eaves can't overhang within 3 feet of the line and the wall must be fire rated within 5 feet; a 5-foot setback avoids those requirements.
• Height: detached ADUs are limited to 2 stories and 25 feet; attached ADUs follow the height limit of the zoning district.
• Utilities: an ADU can have its own meters or share the main house's.

IB 402, dated January 2023, adds two points: the ADU must be in the rear of the lot, and an ADU on separate meters needs its own address. IB 402 predates some of the current page's wording, so confirm both with DSD for your lot. Rules like these get amended, so re-check the ADU page in the month you apply.

How the ADU permit process works

1. Confirm zoning. Look up your district on DSD's OneStop zoning map, linked from the residential zoning page. DSD also says a property must be platted and zoned before construction.
2. Record the owner-occupancy affidavit and covenant. DSD's form must be signed, notarized and recorded with the Bexar County Clerk. The sample covenant runs with the land, tells future owners that the ADU depends on owner occupancy, and requires removing the ADU improvements and restoring a single-family use if a condition of approval is violated.
3. Prepare permit-ready plans. The ADU page lists a site plan, a foundation plan, an IECC-compliant energy report, Manual J HVAC sizing calculations and a Manual S list of proposed equipment. DSD's IB 101 residential permit bulletin adds floor plans, framing details, exterior elevations, a window and door legend and a braced wall plan for accessory dwellings.
4. Apply through BuildSA. Choose the Residential Building Permit Application, select the ADU permit type, and include proof of residency and proof the affidavit was recorded.
5. Completeness and plan review. DSD's ADU fact sheet says the completeness review can take up to three business days. After the plan review fee is paid, the technical review can take up to three business days for initial redline comments. Corrections add time.
6. Permit fees and issuance. Permit fees are applied after approval, and the permit is issued once they are paid.
7. Inspections and occupancy. Once all inspections pass, DSD issues the Certificate of Occupancy and the ADU can be occupied.

How DSD checks owner occupancy

The ADU fact sheet says staff cross-reference ADU and short-term rental applications and post ADU permits online. Confirmed violations can bring fines, criminal charges and, in some cases, loss of utility service to the main house, the ADU or both. DSD's affidavit form also says the owner may not collect rent for the unit the owner lives in. Plan on the owner-occupancy rule lasting as long as you own the property.

Fee waivers for affordable rentals

The ADU page says City development and permitting fees, plus SAWS water and wastewater impact fees, may be waived when the main home or the ADU is rented to a household earning at or below 80% of area median income. Rent can't exceed 30% of the renter's monthly income, and the restriction stays in place for five years after the Certificate of Occupancy is issued.

Rules to check beyond the ADU page

• Zoning and setbacks for your lot. DSD's residential zoning page notes that setbacks vary by zoning district under the Unified Development Code. IB 402 says an attached ADU must meet the setbacks of the main house for its district, which matters when a garage sits close to a side lot line.
• Parking for a garage conversion. The ADU page answers parking only for ADUs. If you are turning garage parking into living space, ask DSD what parking your zoning requires.
• HOA covenants and deed restrictions. Read them before design; they can add limits of their own. DSD's ADU application form asks whether deed restrictions would prohibit an accessory dwelling.
• Historic and conservation districts. Exterior changes may need design review before work starts.
• Rental plans. DSD runs a separate short-term rental permit program, so ask about it early if that is part of your plan.

Building questions for a garage conversion

• Floor level. Garage slabs usually sit lower than the house and slope toward the door. Plan how the floor will be raised or leveled and how moisture will be handled.
• The door opening. The garage door gets framed in, insulated and finished, often with a window or entry door that matches the house.
• Insulation. Garage walls and ceilings are often bare. Plan insulation for the walls, the ceiling and the new infill wall, and ask your designer which energy items DSD will check.
• Comfort. Decide whether to extend the existing HVAC or add a separate system; a licensed air conditioning contractor checks capacity. See how we handle HVAC coordination during a remodel.
• Bedroom use. If the room will be a bedroom, raise window and emergency-exit questions with your designer and DSD during plan review.
• Power and plumbing. For contractor-performed work, new circuits, a bathroom or a kitchenette need trade permits pulled by licensed trade contractors, unless the work is part of an ADU combination permit.

Building questions for a detached ADU

• Foundation design for the clay soils common across the San Antonio area
• Utility routing for water, sewer and electric, and whether the existing electrical service has room or needs a panel upgrade coordinated with a licensed electrician
• Separate or shared meters, keeping in mind IB 402's note that separately metered ADUs need their own address
• Drainage so the new slab doesn't send water toward either building
• Access and privacy between the main house, the ADU and neighbors

What drives garage conversion cost

Garage conversion cost depends more on what the new room has to do than on its square footage. These items move the number most:

• Plumbing. A bathroom or kitchenette usually means cutting the slab for new drain lines, which is often the biggest single swing in price.
• Floor work. Raising or leveling a sloped garage slab and controlling moisture.
• Door infill and windows. Framing in the garage door opening and matching the exterior of the house.
• Comfort. Extending ductwork costs differently than adding a separate system, and the load calculation decides which one works.
• Electrical capacity. New circuits may fit the existing panel, or the conversion may call for a service upgrade.
• Room or ADU. A full ADU adds a kitchen, possible separate meters, the recorded affidavit and a Certificate of Occupancy.
• Fees and paperwork. DSD charges plan review and permit fees from its current fee schedule, and an ADU rented at an affordable rate may qualify for the fee waiver above.

If the conversion is one phase of a bigger project, planning a whole-house remodel in phases can help you budget the pieces in order.

Permits and contractor registration

DSD's residential permits page says a building permit is typically required to build, remodel, repair or demolish a structure. On the contractor side, DSD's registration page lists conversions under the Home Improvement Contractor registration for non-structural work, while structural alterations, additions and detached accessory buildings over 300 square feet require a Residential Building Contractor registration. DSD's pages don't all use the same cutoff for accessory buildings: the residential permits page draws the contractor line at 400 square feet, and DSD's no-permit list exempts one-story detached sheds up to 300 square feet. Confirm the threshold for your structure with DSD.

Before you settle on a conversion, compare it with how a San Antonio home addition gets permitted: lot checks, the drawings DSD reviews, who can apply, plan review, corrections, issuance and inspections. The San Antonio building permit rules explain trade permits and inspections, and the home remodel site visit checklist helps you list rooms, utilities and must-haves before a contractor visit. For drawings, see how we organize construction drawings and permits in San Antonio.

Test your garage or ADU idea

214 Veteran Solutions is a veteran-owned general contractor in San Antonio that plans and manages home additions in San Antonio and remodels, and coordinates licensed trade contractors for the electrical, plumbing and HVAC work. To test your garage or ADU idea against the City's rules, call (210) 796-3695, request an estimate or book an estimate consultation.