Washington · Deck guide
How to build a deck in Washington
Wood or composite deck with railings and stairs. A ground-level deck adds usable outdoor living space. Attached decks over 30" almost always trigger a permit and a footing inspection.
Typical cost
$2,727–$4,331
Time
2–5 weekends
Skill
Intermediate
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Permits & code in Washington
Decks more than 30" above grade almost always require a permit and a footing inspection. Frost line here is 18" — that's your minimum footing depth. Seismic bracing requirements apply to sheds and garages in the western half of the state.
State-level rules only — cities and HOAs frequently add stricter requirements. Always confirm with your local building department before you dig.
What most people get wrong
- Under-sizing the ledger fasteners. A missed ledger is the #1 cause of collapsed decks.
- Not sloping the deck 1/8" per foot away from the house. Standing water rots joists.
- Using construction screws instead of structural (ledger, hanger) screws where they're required.
The 5-step deck plan
- Step 1Confirm site and permit pathLocate property lines, call 811 for utility marking, and check whether your city/HOA needs approval before you break ground.
- Step 2Order materialsUse the shopping list from our planner. Confirm delivery vs pickup — bulk lumber and concrete are usually cheaper delivered.
- Step 3Lay out and prep the siteBatter boards, string lines, level the base. Getting this right saves days later.
- Step 4Frame the structureFollow the cut list. Check for square with the 3-4-5 method every few pieces. Fasten with the right structural screws.
- Step 5Finish and inspectSand, stain/seal, and (if required) schedule your final inspection before backfilling or closing anything up.
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