Washington

Washington Permit Guide for Metal Carports, Garages and Barns

In most of Washington, a metal carport or garage needs a building permit from the city or county where it will sit, because the state code only exempts small one-story sheds and playhouses, not carports or garages. The state building code applies in every county and city, and local building departments enforce it. Under Washington's adopted residential code, a detached one-story storage shed or playhouse can skip the building permit if its floor area is 200 square feet or less, and the commercial code sets that cutoff at 120 square feet. Anything bigger, and any carport, should be treated as permitted work until your local office tells you otherwise. Getting a Washington carport permit usually means a site plan, the building's engineered drawings and a check against local setbacks and snow loads. Farm buildings can be a different story, since Washington lets each county or city decide whether to exempt agricultural structures.

Building code in effect

Washington has one statewide code. Under RCW 19.27.031, the state building code is in effect in all counties and cities, and it is made up of the International Building Code, International Residential Code, International Mechanical Code, International Fire Code and Uniform Plumbing Code, each with Washington amendments adopted by the State Building Code Council. The editions in force today are the 2021 IBC (chapter 51-50 WAC) and the 2021 IRC (chapter 51-51 WAC), which took effect statewide on March 15, 2024. The Council is working on the 2024 editions, and it has announced that the 2024 codes will take effect on May 3, 2027, so permits applied for before then fall under the 2021 codes. Washington did not amend the permit exemption section of either code, so the model code's shed limits (200 square feet under the IRC, 120 square feet under the IBC) carry through. Cities and counties can still add their own local amendments under RCW 19.27.060, which is why it pays to check the local rules.

Who issues permits

Washington does not issue building permits for private garages or carports at the state level. RCW 19.27.050 says the state building code is enforced by the counties and cities, and a county or city without its own building department has to contract with another city, county or inspection agency to do the work. In practice, that means a city building department handles permits inside city limits, and the county's community development or building office handles unincorporated land. Zoning setbacks, critical areas and shoreline rules are also local, so the same office (or its planning side) usually reviews where the building sits on the lot. Before you order, call the office that covers your parcel and ask whether it needs a residential building permit, a commercial permit or an agricultural exemption form.

County permit guides

County guides are coming soon.

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When you need a permit

Garages and enclosed buildings: A detached garage or shop over 200 square feet on a home lot needs a building permit under the IRC as adopted in Washington. On commercial or non-residential property the IBC cutoff is 120 square feet.
Carports: Carports are not on the IRC's list of exempt work, so plan on a building permit. The City of Kirkland, for example, requires a permit for a carport of any size, including kit carports.
Small sheds: A one-story detached storage shed or playhouse of 200 square feet or less (120 square feet on non-residential property) is exempt from the building permit, but it still has to meet setbacks and other local rules.
Electrical and plumbing: The shed exemption does not cover wiring, plumbing or mechanical work. Kittitas County, for instance, says exempt accessory structures cannot contain plumbing or mechanical systems.
Farm buildings: Agricultural buildings are only exempt where the county or city has chosen to exempt them under RCW 19.27.060, and the rules differ from place to place.

Farm buildings

Washington has no blanket statewide permit exemption for farm buildings. Instead, RCW 19.27.060 lets the governing body of each county or city limit how the state building code applies to certain classes of buildings based on use, as long as they are not single-family or multifamily homes. Some counties use that power for barns. Clark County, for example, exempts qualifying agricultural buildings from a building permit if the owner signs an Ag Building Certification form, keeps the building solely for farm use such as hay, livestock or equipment, and still meets zoning setbacks and environmental rules. Plumbing and mechanical permits are still required there, and garages, shops and residential accessory buildings do not qualify. Other counties, such as Kittitas, do not post a general ag exemption at all. Separately, RCW 19.27.065 exempts temporary growing structures used only to produce horticultural plants, which covers hoop houses and similar structures but not a steel barn.

Wind and snow

Washington's weather changes a lot from one side of the Cascades to the other. Mountain and foothill areas can carry heavy ground snow loads, and the IRC leaves the local design criteria for snow, wind and seismic risk to each jurisdiction, so the load your building must meet depends on the county or city. The coast and exposed ridges see strong winter wind storms, and western Washington sits in a high seismic area, which affects anchoring and foundation details. Ask your building department for its design snow load and wind speed before you pick a building, because a rating that works in one county may fall short in the next. Our partnered manufacturers offer certified buildings rated for 140 MPH wind and 35 PSF snow load, and higher ratings can be quoted where required.

Before you order

Call the building department for your city or county and ask for its design snow load and wind speed for your exact address.
Ask whether your lot is in a critical area, floodplain or shoreline zone, since those local rules can change where the building can go.
If you plan to use the building only for farming, ask the county whether it offers an agricultural exemption and what form it requires.
Get engineered drawings for the building size and ratings you want so they are ready for the permit application.

Common questions

Do I need a permit for a carport in Washington?
In most cases, yes. Carports are not on the IRC's list of exempt work, and cities such as Kirkland require a building permit for a carport of any size. Check with the city or county that covers your property.

Do I need a permit for a metal garage in Washington?
Yes, if it is over 200 square feet on a home lot (120 square feet on non-residential property). Garages are enforced by your city or county building department under the 2021 IRC and IBC as adopted in Washington.

Are farm buildings exempt in Washington?
Only where the local government has chosen to exempt them. RCW 19.27.060 lets counties and cities limit the code for certain non-residential buildings, and Clark County uses it for qualifying ag buildings with a signed certification form. Other counties may not, so ask yours.

Will the 2024 codes change anything for my building?
The State Building Code Council has announced that the 2024 codes take effect on May 3, 2027. Until then, permits are reviewed under the 2021 codes that took effect March 15, 2024.

Sources

Permit rules change. Always confirm with your local permit office before you build.

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