Garage Building Permit: What to Expect Before You Dig

Almost every new garage needs a building permit. The model code (the IRC¹, section R105.2) exempts a detached accessory building only when its floor area is 200 sq ft or less and it has one story, and even an exempt building has to meet the code. The smallest garage we draw is the one-car 12x22, which is 264 sq ft, so none of our plans fall under the exemption.

Local rules sit on top of that. States and cities adopt the code with their own changes, and zoning is a separate set of rules about setbacks, height and how much of the lot you can cover. This guide tells you what the office will ask for and what to bring. It cannot tell you your local answer, and the planner says so on every plan: Local approval not checked. Treat the building department as the last step of the design, not the first surprise of the build.

What the Building Department Asks For

The list changes a little from one office to the next, but a garage submission usually has the same pieces. Ask for the office’s checklist, then assemble these.

The Drawings

• A site plan. The lot outline, the house, the new garage and the distance from each wall to the property lines. This is the sheet that shows the setbacks.
• A floor plan and elevations. Overall dimensions, door and window openings, wall height and roof pitch.
• A foundation detail. The slab thickness and edge, and the footing depth. We explain how the foundation works in our garage foundation guide.

The Documents Other People Supply

• Truss drawings. Trusses are engineered by the manufacturer. The IRC (R802.10.1) says the truss design drawings go to the building official and are approved before installation, and they arrive with the trusses. Ask the truss supplier for them when you order, so you have them for the inspector.
• The header calculation for the big door. A 16 ft garage door is wider than anything in the IRC header table (R602.7), whose largest combination of dimensional lumber cannot span it. The beam over a door that wide is an LVL, and the office wants to see how it was sized. Our plan prints the calculation: the load on the header, the maker’s table value it is checked against and the jack studs for the bearing. Some offices also ask for the LVL supplier’s sizing sheet.

The Three Loads

Every plan we draw uses three numbers that depend on where you build: ground snow load, design wind speed and frost depth. You do not look them up on a map and guess. Your building department assigns them, and it will tell you which values it wants on the plans. Ground snow above 70 psf is outside the prescriptive rules and needs an engineer (IRC¹ 2021 R301.2.3).

Setbacks and Fire Separation

Two different sets of rules decide how close to the property line a garage can sit, and both have to pass.

The Fire Separation Rule

For a detached garage the IRC¹ (R302.1, Table R302.1(1)) works by distance to the lot line:

• A wall with no fire-resistance rating must be at least 5 ft from the line.
• A wall built as a 1-hour fire-resistance wall can sit on the line.
• Openings (windows and doors) are not allowed in a wall closer than 3 ft.
• Eaves are not allowed closer than 2 ft, and between 2 and 5 ft the underside of the eave needs 1-hour protection.

If the garage serves a house with a fire sprinkler system, the second table (R302.1(2)) relaxes this: a wall with no rating can sit 3 ft from the line, and a garage within 2 ft of the line can have eaves of 4 in or less. Unless you know the house is sprinklered to that standard, plan around 5 ft.

Zoning: Setbacks, Height and Coverage

Zoning is the part the model code does not cover. A city may require the garage to be behind the front of the house, set back a fixed distance from the side and rear lines, under a maximum height and inside a limit on the total area of outbuildings on the lot. Those limits are local, and sometimes they are stricter than the 5 ft rule. Ask your zoning office for the rules for your lot, then draw the garage on the site plan to match them. The garage designer lets you try a size against the lot before you commit.

Inspections in Order

The sequence differs by office, and some skip steps for a simple building. Typically a garage goes through three kinds of inspection, and the work stops until each one passes:

1. Footing or slab, before the concrete

   The inspector checks the excavation, the footing depth where one is required, the gravel base and the reinforcement before you pour.

2. Framing

   Walls, headers, bracing, truss installation and the anchors that hold the building to the slab, before any cover goes over them.

3. Final

   The finished building against the approved plans.

Keep the approved plans and the truss drawings on site for every visit, and ask the office how far ahead it wants each inspection booked.

What a Permit Costs

We do not quote a permit price, because we have no source for a number that holds across the country, and any single figure would be wrong for most readers. Here is how the fee is set instead.

Each jurisdiction publishes a fee schedule. Most charge either a percentage of the declared value of the work or a rate by floor area, and many add a plan review fee and a charge per inspection. Zoning review, a survey, a soil test or an engineer’s stamp can come on top. Your office’s schedule gives the real figure, usually on a web page or a printed sheet at the counter.

Our cost estimates leave permits and fees out of the total for exactly this reason: the fee depends on your address. When you budget, build the permit line yourself from the local schedule. Our cost to build a garage guide shows what the build itself costs, priced from the store and labor sources it names, and what it leaves out.

In Canada

The planner has a Canadian mode that follows the National Building Code² (NBC 2020), and permits there are municipal, not provincial. The common pattern is a permit above a small floor area, then setbacks, height and coverage rules set by the city’s zoning bylaw.

Two municipalities as examples, from the city documents we read in October 2026:

• Toronto: the zoning bylaw (569-2013, chapter 10.5) requires a permit for a garage or accessory building above 10 m², and caps height at 4.0 m, or 2.5 m when it sits less than 1.8 m from the house.
• Calgary: a building permit is needed above 10 m², the rear setback is 0.6 m and the maximum height is 4.6 m.

These two are samples, not a Canadian rule. Vancouver and Montreal we could not verify, and every other city has its own numbers, so check yours.

The foundation is different too. A detached one-story garage under 55 m² (592 sq ft) without masonry can sit on a 100 mm (4 in) slab under NBC² 9.35.3.1. Above 55 m² the building code asks for footings below frost or an engineered slab, and some cities, including Calgary⁴, ask for an engineered slab. The one-car sizes, the 20x20 and the 24x24 are under the 55 m² line, and the 24x30 is over it.

Take the Drawings to the Counter

The permit office wants drawings, and good ones shorten the review. The builder’s plan for any of our garages gives you the dimensioned plan, the framing and the foundation layout for the size you chose, with the loads you entered. At $79 it is a small part of the project, and it comes with preliminary checks for the code items we can verify. It does not replace your local approval: the checks say what we did and did not verify, and the local items stay marked as not checked.

To see what goes on a plan before you pay, start with a size in the garage designer, or open the 24x24 garage plan for a common detached layout. If you are still deciding between sizes, our detached garage plans page compares them. Draw the garage, take the plan and the site sketch to the office and ask what else it needs.