Do You Need a Permit for a Carport in Snohomish or King County? (2026 Guide)

If you’re planning a carport in Snohomish or King County, the first question is usually the same one we get about sheds and garages: do you actually need a permit for this? The honest answer is “it depends on size and location,” and getting it wrong can mean a stop-work order after the concrete is already poured. Here’s what the two counties’ own rules actually say.

Snohomish County: size and location both matter

In unincorporated Snohomish County, a detached carport (not attached to your house) is exempt from a building permit if it stays under 200 square feet inside an Urban Growth Area or 400 square feet outside one, per the county’s Common Permit Exemptions bulletin. Most driveway carports fall well under that first threshold — a single-car carport is typically 12×20 (240 sq ft), which already crosses the 200-square-foot UGA line, so plenty of “small” carports still need a permit once you’re inside city growth boundaries.

Even an exempt carport isn’t a free-for-all. The county still holds exempt structures to height limits — 9 feet inside the UGA, 11 feet outside it — and to the same setback and environmental rules as anything else on your lot. Skipping the permit doesn’t skip the code.

King County: the 200-square-foot line, plus your city’s own rules

Unincorporated King County follows the same general idea: an unconditioned accessory structure like a carport under 200 square feet is generally exempt from a building permit. But “unincorporated” is the key word — if your property sits inside a city (Bothell, Kirkland, Redmond, Snohomish, and so on), that city’s own permit desk sets the rule, not the county’s. Some cities mirror the 200-square-foot exemption; others don’t exempt carports at all. The only way to know for certain is to check with your specific city’s permitting office before you build.

What “exempt” doesn’t mean

A permit exemption is about paperwork, not about the rules disappearing. Setback distances from your property line, height limits, and (for anything near a slope, wetland, or shoreline) environmental review still apply whether or not a permit is required. We’ve seen homeowners build a technically permit-exempt carport that still had to be moved because it violated a side-yard setback — the size exemption didn’t cover that.

It’s also worth knowing that snow and wind load still matter structurally even on a small, permit-exempt build. Western Washington’s snow loads are modest compared to the mountains, but a carport built without proper post spacing and header sizing can still fail under a wet, heavy snow load — permit or no permit.

Attached vs. detached changes the answer

Everything above is about a detached carport — a standalone structure not touching your house. Attach a carport to your home (sharing a wall or roofline), and both counties generally treat it differently: attached structures typically lose the small-structure exemption and need a permit regardless of square footage, because you’re now tying new construction into your home’s existing structure and roof drainage. If your plan is a carport off the side of the garage or house rather than a freestanding one in the driveway, budget for a permit from the start.

There’s also a practical wrinkle with open-sided structures specifically: a carport, by definition, has at least one open side (that’s what makes it a carport instead of a garage). Some jurisdictions measure “footprint” differently for open structures than fully enclosed ones, and a few require the open side to face away from the property line it’s closest to. It’s a small detail, but it’s exactly the kind of thing that gets missed on a DIY permit check and caught on a professional one.

Why get it checked even when you don’t need a permit

Because the permit threshold depends on exact square footage, exact location (inside or outside a UGA, inside or outside a city), and sometimes the specific jurisdiction’s own add-on rules, the safest move is to have someone who pulls permits in Snohomish and King County regularly tell you where your project actually lands before you start. Getting it wrong in either direction costs you — either an unplanned permit process mid-build, or a structure you have to alter later because a setback or height limit got missed.

We build custom carports and garages across Snohomish and King County and handle the permit determination as part of the process, not as a surprise halfway through. If you’re weighing a carport against a fully enclosed detached garage for the same footprint, that’s worth a conversation too — the right call depends on what you’re parking or storing and how much of the space you want weather-tight.

Want a straight answer on what your specific lot allows, in Snohomish or King County? Get in touch and we’ll walk you through it before you commit to a design.

Permit thresholds cited above come from Snohomish County’s Common Permit Exemptions bulletin and King County’s residential accessory structure guidance as of 2026 market research; always confirm current rules with your local permitting office before building, since city-level rules can differ from the county baseline.