Barndominium with Shop Floor Plans in Washington State

A shop is the reason many Washington buyers want a barndominium: room for a pickup and trailer, a tractor, a boat or a trade business under the same roof as the house. East of the Cascades, where acreage is bigger and pole barn buildings are the local habit, the shop is often the larger half of the building. The plan choices that matter are the ones that are hard to change later: how big the bay doors are, what wall separates the shop from the bedrooms, where the shop's floor and roof water goes, whether the shop is heated, and whether the county's zoning allows the business you plan to run from 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.

Bays sized for trucks, trailers and equipment

Measure the tallest and widest thing you will ever park: a lifted pickup with a rack, a stock or boat trailer, a tractor with a loader, a combine header on the dry side. Size the overhead door and the eave height to that, with clearance, and allow enough depth to close the door behind a truck and trailer. A clear-span steel or pole barn shop has no interior posts to steer around, which is the main reason to build the shop this way.

The wall between the shop and the bedrooms

Table R302.6 of the 2021 International Residential Code, which Washington adopts, calls for at least 1/2-inch gypsum board on the garage side of the wall separating a garage from the house and attic, and 5/8-inch Type X gypsum board under any habitable room above. Section R302.5.1 bars any opening from the garage straight into a sleeping room, and other doors must be solid wood or steel at least 1 3/8 inches thick, or 20-minute fire-rated, and self-closing. A mudroom between the two keeps wet boots and the shop door away from the bedroom hall.

Keep shop and roof water off the septic

Washington's on-site sewage rule, WAC 246-272A-0230, requires that footing drains, roof drains and other non-sewage drains be kept out of the septic system, the drainfield area and the reserve area. The shop's big roof and any floor drain need their own route. Where the shop serves a business, the designer must show its sewage is not industrial wastewater, so plan the floor drain separately or leave it out.

Heated or not, decide early

If the shop is heated as part of the house, its floor area may count as conditioned floor area, which is what Washington's energy code measures when it sets the credit target: 5.0 additional efficiency credits for a dwelling under 1,500 square feet with less than 300 square feet of fenestration, 8.0 for most homes and 9.0 above 5,000 square feet. Ask the building department how it will treat the shop, and decide early, because the answer sets the wall and roof insulation before the frame is ordered.

What changes when the shop joins the house

Attached, the shop is reviewed like a garage; detached, it may not need water at all

A shop under the same roof as the living space is reviewed with the house, and building departments commonly treat it under the residential code's garage rules: a separating wall and ceiling, protected doors and a floor that drains. Washington adds its own rule for new dwellings with an attached private garage: WAC 51-51-0309 requires at least one dedicated 40-ampere, 208/240-volt branch circuit for electric vehicle charging, unless there is no utility power. A detached shop is a different question. RCW 19.27.097 makes a permit applicant show an adequate water supply for a building that needs potable water, and exempts buildings that do not; a shop with no sink or toilet can stay outside that requirement, while one with a bathroom cannot.

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.

Equipment shop with an end-wall house

2,400 sq ft shop (40' x 60') / 1,200 sq ft living (30' x 40')

A tall 40x60 shop with a wide end door for trucks and equipment, joined to a single-story house through a mudroom and laundry. The shop has its own walk door, its own drain plan and an electrical subpanel installed by a licensed trade contractor; the house side carries the septic connection and a covered entry.

Side-by-side under one roofline

1,800 sq ft shop / 1,800 sq ft living

One long building split down its length, with shop bays along one side and the house along the other under a continuous gable roof. The shared wall is the fire separation and the sound barrier. A covered porch runs along the house side and faces away from the shop apron, and gutters on the shop side carry roof water away from the drainfield.

Home business shop with office

1,500 sq ft shop / 300 sq ft office and restroom / 1,700 sq ft living

For a trade business run from home. A front office and restroom keep visitors out of the house. Whether a business can operate from the shop is set by county or city zoning, so confirm the home occupation with the planning office before a customer entrance or a sign is drawn.

Ways to build this

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

Shouses

Shop houses (shouses) in Washington State: a working shop and a home under one roof, planned around county zoning, septic, water and the energy code.

Pole Barn Homes

Pole barn homes and pole barn house kits for Washington State: post-frame buildings with a shop and living space, designed to your county's snow load.

Steel Construction

Steel and metal building construction in Washington State: red-iron frames for barndominiums and shops, designed to your county's snow and seismic values.

Custom Plans

Custom barndominium plans for Washington State: floor plans and permit drawings with the energy code credits and your site's design values built in.

Barndominium with a Shop: 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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Does an attached shop count as a garage?

Building departments commonly review an attached shop that houses vehicles under the residential code's garage rules. That brings the dwelling-garage separation in Table R302.6, the door rules in R302.5.1, and a floor of noncombustible material sloped toward a drain or the main vehicle door under R309.1. In Washington, a new dwelling with an attached private garage also needs a dedicated 40-ampere, 208/240-volt circuit for vehicle charging under WAC 51-51-0309.

Does a detached shop need a well or water hookup to get a permit?

Only if it needs potable water. RCW 19.27.097 requires evidence of an adequate water supply for a building that necessitates potable water and exempts buildings that do not need potable water facilities. A shop with a bathroom or a sink is on the water side of that line.

Can the shop floor drain go into my septic system?

Plan on no. WAC 246-272A-0230 keeps footing drains, roof drains and other non-sewage drains out of the septic system and its drainfield and reserve areas, and a system serving a business must be shown to receive sewage, not industrial wastewater. Many owners leave the floor drain out; others settle a separate arrangement with the local health jurisdiction before the slab is poured.

Can I run a business out of the shop?

Often, with local approval. Home occupations are regulated by county and city zoning, and the rules on employees, customer visits, signs and outdoor storage vary between jurisdictions. Ask the planning office before the plan shows a customer entrance.

What fire separation does the wall between shop and house need?

Treat it like an attached garage: at least 1/2-inch gypsum board on the garage side of the separating wall, 5/8-inch Type X under any habitable room above, no opening from the garage into a sleeping room, and a solid wood or steel door at least 1 3/8 inches thick, or a 20-minute rated door, between the two.

How big should the shop door be?

Big enough for the largest vehicle you expect to own, not just the one you own now. Measure width with mirrors out and height with racks, a loader or a boat's tower, then add clearance. On a clear-span building the door width is limited mainly by the header over it, so settle it before the frame is ordered.

Where this plan fits in Washington

West of the Cascades a plan answers to rain and seismic design; east of them, to snow, sun, dry acreage and wildfire. These are the areas this layout suits best.

Spokane County

The state's pole barn market, where a big shop beside or under the house is the norm on acreage.

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Stevens County

Rural northeast Washington parcels where equipment storage often matters more than floor area.

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Yakima County

Orchard and farm country where a shop-house has to hold tractors, trailers and tools.

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Grant County

Columbia Basin acreage with room for a wide shop and a long apron.

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Spokane

Pole barn country around Spokane, where a big shop beside or under the house is a common plan.

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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 references on this page are to the 2021 International Residential Code as amended by Washington (chapter 51-51 WAC) and the 2021 Washington State Energy Code, Residential (chapter 51-11R WAC), in force since March 15, 2024. The State Building Code Council has scheduled the 2024 editions to take effect May 3, 2027; the edition your permit is reviewed under governs.

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