Barndominium Floor Plans with Garage in Idaho

An attached garage is almost standard on an Idaho barndominium. Nobody wants to scrape a windshield at six in the morning in January, and a garage under the same steel roof costs far less than a separate building. It is also the one part of the plan where Idaho's own amendments change what the model code says. The wall and ceiling between the garage and the house get heavier protection here than in the national code, and the doors, ducts and egress path around that wall all have rules. None of it is difficult if the garage is drawn with the house, not added to it.

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What actually changes with this feature

The look is the easy part. These are the decisions that follow from it.

The door between garage and house

No opening may go directly from the garage into a room used for sleeping. The door into the house must be solid wood or solid or honeycomb-core steel at least 1 3/8 inches thick, or a 20-minute fire-rated door, and it must be self-closing or automatic-closing. Most plans put it into a mud room or laundry, which is where you want the boots to come off anyway.

Ducts that cross the separation

Ducts in the garage, and ducts through the walls or ceilings that separate it from the house, must be at least No. 26 gage sheet steel or another approved material, with no openings into the garage. Keep the furnace and the ventilation system's ducts on the house side of the wall and the job is simple.

Put the overhead doors where the snow is not

A steel roof sheds snow in sheets off the eaves. Overhead garage doors under an eave get a pile in front of them after every storm, and a door header that collects meltwater can ice up. Where the lot allows, put the doors on a gable end, or protect them with a lower roof sized for the snow that slides onto it. Where your city or county runs a building program, its building official sets the ground snow load for your site.

A floor that drains, and a way out that does not use it

Garage floors must be noncombustible and slope toward a drain or the vehicle door. The house's required egress path must reach the exit door without passing through the garage, so the garage cannot be the only way out of the living space.

Idaho's amendment to the garage table

5/8-inch Type X on the garage side, not 1/2-inch board

Idaho deletes the 2018 International Residential Code's dwelling-garage separation table and replaces it with its own. Between the garage and the residence, its attic, and any habitable room above the garage, Idaho calls for at least 5/8-inch Type X gypsum board or equivalent on the garage side. The model code allowed 1/2-inch board at the wall. Where a detached garage sits less than 3 feet from a dwelling on the same lot, the same 5/8-inch Type X board goes on the interior side of the exterior walls within that area.

Common ways to build this

Three common ways to lay this out. Yours does not have to match one exactly — this is a starting point for the conversation, not a catalog.

Two-car garage off the mud room

40' x 76' / 1,900 sq ft living / 24' x 30' two-car garage

The garage takes one end of the building, doors on the gable end. The door into the house opens to a mud room with laundry and a half bath, and the house has its own front door on the long side.

Three-bay garage for trucks and toys

2,200 sq ft living / 36' x 30' three-bay garage

Two car bays and a deeper third bay for a boat or a side-by-side. The third bay can be taller for a trailer. Keep fuelled equipment on the garage side of the separation.

Bonus room over the garage

1,800 sq ft living / 24' x 32' garage / 600 sq ft bonus room above

A guest room, office or playroom over the garage. Idaho's table puts 5/8-inch Type X board under that habitable room and also lists the structure that carries its floor, and a guest room there needs its own escape window.

Ways to build this

This layout can go together several ways. These are the service lines most relevant to it.

Custom Plans

Custom barndominium plans for Idaho land, drawn around your site, snow load and zoning, and the Idaho residential code your building department enforces.

Turnkey Builds

Turnkey barndominiums in Idaho, from raw land to move-in: zoning, septic, well, snow load and permits handled in the order each has to come.

Shouses

Shop houses in Idaho: a heated working shop and a home under one roof, planned around your zoning, snow load and the residential code.

Barndominium with a Garage: common questions

6 questions worth settling before this plan is drawn. If yours is not on the list, put it in the survey.

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What fire separation does Idaho require between a garage and a house?

Idaho's version of the dwelling-garage table requires at least 5/8-inch Type X gypsum board or equivalent on the garage side, separating the garage from the residence, its attic and any habitable room above. That is heavier than the model code's 1/2-inch board at the wall.

Can a bedroom door open into the garage?

No. The code does not allow any opening from a private garage directly into a room used for sleeping. Other doors between the garage and the house must be solid or steel and at least 1 3/8 inches thick, or 20-minute rated, and self-closing.

Is a carport treated differently from a garage?

A carport must be open on at least two sides. If it is enclosed on more than that, the code treats it as a garage, with the separation and door rules that come with it. In snow country, a carport also needs to be sized for the snow that slides onto it from a higher roof.

Should the garage be attached or detached?

Attached saves a walk through the snow and shares the steel roof. Detached keeps fuelled vehicles and equipment away from the house, which the Idaho Department of Lands recommends on land at risk of wildfire. Note that Idaho's table still asks for 5/8-inch Type X board inside a detached garage's walls if it stands less than 3 feet from the house.

Does a heated garage have to meet the energy code?

Idaho amends the energy code's definition of conditioned space so that it does not apply to garage spaces heated only for frost protection or intermittent use. A garage kept just above freezing sits outside the house's energy envelope; the wall between garage and house does the insulating.

How deep should a barndominium garage be?

Deeper than a town garage. A full-size pickup, a bench along the back wall and room to walk around both usually need 26 to 30 feet. If a trailer or boat goes in one bay, measure it with the hitch and add walking room.

Keep reading

The pages that answer the next question this one raises.

Barndominium with shop floor plans

When the garage becomes a working shop: RV bays, equipment doors and how Idaho's energy code treats a heated shop.

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Permitting

Finding out who permits your parcel, from the city or county building program where there is one to the health district's septic permit.

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Want this drawn for your program and your parcel? That is where a build actually starts.

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Sources

Code figures on this page are from the 2018 International Residential Code as Idaho adopts and amends it (the Idaho Residential Code), and from Idaho's septic rules as read in September 2026. The code in force when your plans are reviewed governs. Snow load and frost depth are set locally, by the building official where your city or county runs a building program.

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Tell us what you want to build and we will draw this for your program, then confirm what it looks like on your parcel, which office permits it, and a realistic budget range. That conversation costs nothing.

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