Most low decks here go up without a building permit. Most raised ones do not. The line is 30 inches off the ground, and it is worth knowing which side of it your deck sits on before anyone digs a footing.
The short answer
If the deck surface sits more than 30 inches above the ground at any point, plan on a building permit in unincorporated Snohomish County. A low, uncovered platform close to the ground usually does not need one. That is the rule in two sentences. The rest of this page is the fine print that decides the close calls.
When you DON'T need one
The county has a work-exempt-from-permit rule, and low decks are on the list. An uncovered residential deck is exempt when it is not more than 30 inches above the ground at any point, is not built over a story or basement below, and is not part of an accessible route into the house. Hit all three and the deck itself does not need a building permit. Measure at the low spot of the yard, not at the back door. A deck that is 20 inches off the patio can be 40 inches off the grass where the yard falls away, and the worst point is the one that counts.
When you DO need one
Anything over the 30-inch line needs a permit. So does a deck over a walkout basement or a lower story, and so does a roof or cover over the deck, even a partial one. Once a deck is tall enough to need guardrails and stairs, the county wants eyes on the framing and the footings, which is fair, because that is the part holding you up. A second-story deck off the kitchen is the classic case. Height also moves the price, which we cover in what drives the cost of a deck.
Exempt does not mean unregulated
Skipping the building permit does not mean the deck can go anywhere. Property-line setbacks still apply. So do critical-area and shoreline rules if the lot touches a stream, wetland, or steep slope, and so do HOA rules if you have one. A permit-exempt deck built into a setback can still be ordered moved, which is a bad afternoon for everyone. Check the lot lines before the first footing goes in, not after the last board goes down.
City limits are different
Everything above is the rule for unincorporated Snohomish County, where Snohomish County Planning and Development Services (PDS) runs the permit counter. Inside city limits it is a different desk. Everett, Lynnwood, Marysville, Mukilteo, Edmonds, and the other cities each run their own building department, and the thresholds can differ. If your house is inside a city, confirm with that city before you lean on the 30-inch rule.
How we handle it
If a deck we build needs a permit, we file it. We check the height, the setbacks, and which permit counter your address answers to, then we handle the paperwork and meet the inspector as part of the job. You do not take a day off to stand in line. Doing a fence too? Fence permits follow their own rules. And once the permit question is settled, the next one is usually composite or cedar.
Common questions
Send a photo of where the yard falls away and we'll measure the worst point before anyone digs a footing. Permit or not, the setbacks, the footings, and the framing all land in one written quote.
