Do you need a permit to build a garage?

The International Residential Code, the model code most states build on, exempts one-story detached accessory buildings up to 200 square feet of floor area. A 10 by 20 foot space is already 200. Most one-car garages are bigger, and two-car garages are much bigger. If you’re building a small storage building instead, see do I need a permit for a shed.

Garages also have code rules of their own, which is why reviewers want drawings:

• A noncombustible floor, sloped toward a drain or the vehicle door
• Fire separation for an attached garage: at least 1/2-inch gypsum board on the garage side, separating it from the house and attic, and 5/8-inch Type X board under any rooms above
• A solid or fire-rated door into the house, self-closing and self-latching, and no door into a bedroom
• Separation for a detached garage built less than 3 feet from the house

Some states set larger exemptions. Pennsylvania’s statewide code, for example, doesn’t apply to detached private garages and carports under 1,000 square feet that go with a single-family home, though a municipality can still regulate them by local ordinance. Local rules decide.

Here’s how each type is usually treated. Your jurisdiction may differ.

A pole barn used as a garage, a shop or storage for your home is usually permitted like any other accessory building of its size.

Genuine farm buildings are different in some places. Some states and counties exempt agricultural buildings from the building code. Pennsylvania’s statewide code, for example, doesn’t apply to agricultural buildings, which it defines as buildings that store farm implements, hay, feed or grain or house livestock, not habitable space or places open to the public. These exemptions usually depend on how the building is used, and they often don’t cover zoning, floodplain or electrical rules. Expect to be asked what the building is for.

Pole barn permit drawings

Beyond the usual site plan, floor plan and elevations, reviewers commonly look for the post layout and spacing, the post embedment and footing detail, the truss and purlin layout, wall girts and bracing, and a building section. Post-frame kits and trusses are often engineered by the supplier or truss manufacturer. Include their drawings, and see when you need an engineer’s stamp if your design goes beyond them.

In the model residential code, a carport must be open on at least two sides. If it’s open on fewer sides, it’s treated as a garage. Beyond that, carport permit requirements vary. Some places exempt small freestanding carports, while others require a permit for any roofed structure. Setbacks usually still apply, and a carport attached to the house may have to meet the house setbacks.

Metal carports and prefab steel garages are often sold with drawings engineered for a specific wind speed and snow load. Ask the supplier for drawings that match the design values at your site, then show how the building anchors to its foundation or slab.

For a typical detached garage, expect to submit:

• Site plan: the garage, house and property lines, with setbacks, driveway and easements. See how to draw a site plan.
• Foundation plan: slab thickness, footings, and anchor bolts or hold-downs
• Floor plan: overall dimensions, doors, windows and the floor slope
• Elevations: every side, with the height and roof pitch
• Framing section: footing to roof, including the header over the overhead door and the wall bracing beside it
• Electrical plan: receptacles, lighting and the feeder or subpanel, if you’re running power

Add truss drawings if you use trusses, and energy forms if you’ll heat the space. The building permit drawings checklist explains each sheet.

Can you build a garage without a permit? Only where your jurisdiction exempts it. Otherwise, you take on risks that often show up later:

• Stop-work orders and fines, and in some places higher permit fees when you apply after the fact
• Opening up finished work so an inspector can see the footings, framing or wiring, or removing the building
• Problems when you sell, refinance or file an insurance claim involving the building

If it’s already built, ask your building department how to legalize it. Dealing with it on your own terms is usually easier than having it come up during a sale.

1. Find your jurisdiction: usually the city inside city limits, the county outside them.
2. Ask for the residential accessory building or garage checklist.
3. Describe the building: size, height, attached or detached, use, foundation, and whether it has power, water or heat.
4. Ask for design values: wind speed, snow load and frost depth.
5. Check zoning and your HOA for setbacks, height and appearance rules.
6. Get the answer in writing, or note who you spoke with and when.

AI CAD PRO is free garage plan software for Windows. Describe your garage, pole barn or carport, and the AI assistant helps you draw the site plan, floor plan, electrical plan, elevations and sections as editable CAD objects. Attach your survey, a kit supplier’s drawings or your department’s checklist as references, and export a PDF set that matches the print preview.

It doesn’t size beams, trusses or posts, and its drafting checks aren’t a code review. Your building department decides what you need.