Do You Need a Permit for a Shed in Snohomish County? (2026 Guide)

If you’re planning a new shed, garage, or storage building in Snohomish County, one of the first questions we hear from homeowners is simple: “Do I even need a permit for this?” The answer depends almost entirely on square footage — and getting it wrong can mean fines, a stop-work order, or having to tear down and rebuild. Here’s what Snohomish County’s own permit rules actually say, so you know where you stand before you start.

The 200 Square Foot Rule (and When It’s 400)

In unincorporated Snohomish County, a single-story shed or storage building that isn’t used for human habitation is exempt from a building permit if it’s 200 square feet or smaller inside an Urban Growth Area, or 400 square feet or smaller outside one. That covers most backyard sheds — a 10×20 storage shed, for example, sits right at that first threshold.

“Exempt” means you don’t need to pull a building permit for the structure itself. It does not mean the shed can go anywhere on your lot, or that every rule disappears.

What the Exemption Doesn’t Cover

Even a permit-exempt shed still has to meet the county’s setback requirements from other buildings, structures, and property lines. And there’s one rule that surprises a lot of homeowners: permit-exempt accessory structures can’t have a heating system installed. If you’re picturing a heated and insulated backyard office or studio, that project is outside the exemption regardless of its square footage, and it needs a permit.

Sheds used for anything other than storage — a workshop with plumbing, a habitable space, anything tied into your home’s utilities — also tend to trigger full permitting, even under 200 square feet. When in doubt, it’s worth a five-minute call before you order materials.

Garages and Larger Storage Buildings

Once you’re past shed territory and into a detached garage or a larger storage building, different numbers apply. Storage buildings and garages up to 2,400 square feet in footprint are permitted outright in every zone classification, subject to the standard zoning setbacks for that zone. On lots under 5 acres, though, the county caps the combined footprint of all your accessory and non-accessory garages and storage buildings at 6,000 square feet total — worth knowing if you’re planning a garage now and a shop building later.

Setbacks scale with size, too: buildings with a footprint over 2,400 square feet need at least 15 feet from any external property line, and anything over 4,000 square feet needs at least 20 feet. If you’re building a custom garage or a carport near a property line, this is the number that decides how close you can actually get.

Building in King County? The Same Question, Different Numbers

If your project is in King County rather than unincorporated Snohomish County, the exemption thresholds and setback rules are set by that jurisdiction, not the ones above — the same question applies, but you’ll want the numbers for your specific city or the unincorporated county. It’s one more reason a site-specific check beats guessing from a blog post (including this one).

The same is true if your Snohomish County property sits inside a city rather than the unincorporated county — Marysville, Lake Stevens, Mill Creek, and other incorporated cities each run their own permitting department, and a city’s rules don’t have to match the county bulletin word for word. “Snohomish County” on a permit question can mean three or four different rulebooks depending on the address, which is exactly why we start every quote with the parcel, not a general rule.

Why This Is Worth Getting Right Before You Build

Building without a required permit in Snohomish County can mean a stop-work order mid-project, retroactive permit fees, or being asked to remove or modify a structure that’s already built. It can also come back to bite you at resale, when a buyer’s inspector or the county flags an unpermitted structure on the property. None of that is worth the time saved skipping a phone call up front.

It’s also worth remembering that “exempt from a building permit” and “exempt from every rule” are two different things. Zoning, setbacks, and the no-heat restriction on exempt structures all still apply whether or not a permit is required — the exemption just means you skip the building-permit application and inspection process for the structure itself. A shed that meets the size cutoff but sits three feet from the property line, or one with a wood stove tucked in the corner, can still be a code violation even without a permit in the picture.

How We Handle This for You

Every custom shed we build in Snohomish County starts with a look at your lot — size, zoning, and where the structure will actually sit — so you know before we start whether you’re inside the exemption or need a permit pulled. The same goes for larger projects: if you’re weighing a detached garage or carport instead of a shed, the size and setback math above is exactly what we walk through with you first.

Every lot is a little different, so the numbers above are a starting point, not a substitute for a site visit. If you’re ready to find out what applies to your property, get in touch with our team and we’ll give you a straight answer before you spend a dollar on materials.

Sources: Snohomish County Assistance Bulletins — “Residential Garages and Storage Buildings” and “Common Building Permit Exemptions” (snohomishcountywa.gov), and Snohomish County Code §30.50.103. Figures reflect county-published thresholds as of 2026 and are general information, not project-specific guidance — always confirm against your parcel and current code.