Permit briefing
Do you need a permit for a garage?
A detached garage needs a permit under the International Residential Code once it passes 200 sq ft of floor area, and walls near a lot line need a fire rating.
The reliable short answer
Size and place it before drawing it: floor area decides the permit, the distance to each lot line decides how the walls are built, and in central Austin the floor-area cap decides whether it fits.
Planning complexity
High
Local answer required
Yes
The model code’s answer
Do I need a permit for a detached garage?
Yes, once it passes 200 square feet of floor area, a 10-by-20-foot footprint, under the International Residential Code. The code calls a detached garage accessory to the dwelling, and it exempts a one-story detached accessory structure only up to that size. A garage that needs a permit is also built to the code's fire lines: a wall less than 5 feet from a lot line carries a one-hour rating, no opening goes in a wall less than 3 feet from one, and within 3 feet of the house the garage's walls get half-inch gypsum board inside.
| Rule | What it exempts |
|---|---|
| Model code (IRC R105.2) | Up to 200 sq ft of floor area, one story, detached |
| Austin | 200 sq ft and 15 ft, as for any accessory structure |
| Los Angeles | No garage line; sheds and similar uses to 120 sq ft |
Austin holds a garage to its accessory-structure line, 200 square feet and 15 feet with no plumbing. Inside the central area its residential design standards cover, a garage also counts toward the lot's floor-area cap, the greater of 40 percent of the lot or 2,300 square feet, unless it earns an exemption: up to 450 square feet as a detached rear garage at least 10 feet from the house, or 200 closer in. Los Angeles's small-building line stops at 120 square feet, and its zoning puts a detached garage on the rear half of the lot.
A three-step permit decision
1. Check it against 200 square feet
The model code and Austin exempt a one-story detached accessory structure up to 200 square feet of floor area, a 10-by-20-foot footprint, and Austin adds 15 feet of height, no plumbing and no flood hazard area. Los Angeles's nearest line stops at 120. Past those lines, a garage is a permitted building.
2. Measure to every lot line
Under the model code, a garage wall less than 5 feet from a lot line is built to a one-hour fire-resistance rating, with no openings in it less than 3 feet from the line and no projections less than 2 feet from it, though a detached garage within 2 feet of the line may keep 4-inch eaves. Within 3 feet of the house, its walls in that zone get half-inch gypsum board inside.
3. In central Austin, count it against the lot
Inside the area Austin's residential design standards cover, bounded by Highway 183, Ben White Boulevard, Interstate 35, William Cannon Drive, Manchaca Road, Loop 360 and Loop 1, a lot's gross floor area is capped at 40 percent of its area or 2,300 square feet, whichever is greater. A detached rear garage at least 10 feet from the house leaves up to 450 square feet out of that count, and one closer to the house up to 200.
What Austin and Los Angeles say about a garage
Austin
- No permit
- Only a garage that fits the accessory-structure line: one story, 200 square feet of floor area or less and no more than 15 feet high, with no plumbing, not a dwelling and outside flood hazard areas. A 10-by-20-foot garage is already at that line.
- Permit
- A larger garage needs a permit. The city's residential forms name garage conversions but not new garages, so ask Development Services, at 512-978-4000, which form a new one takes; on a lot with a septic system, adding a garage also needs an on-site sewage facility review.
Los Angeles
- Ask the city
- The code has no garage line. A garage of 120 square feet or less would have to pass as one of the similar uses in its line for sheds and playhouses, outside Fire District No. 1 and without heating, plumbing or electrical installation, and that call is LADBS's.
- Permit
- A garage over 120 square feet needs a permit. Zoning then puts a detached garage on the rear half of the lot, unless the code allows it in the front yard of a sloping lot, at least 10 feet from the house in most layouts and 10 feet from an alley's center line.
- Fees
- LADBS sets a garage's permit fee from its valuation.
What to have ready before you call
- Floor area and height as drawn
- Distance from each wall and eave to the nearest lot line
- Distance to the house, and any breezeway between them
- Driveway access and any new curb cut
- Circuits for lights, the door opener or an EV charger
- Zoning district, and in Austin whether the lot is inside the design standards area