Do you need a permit for a deck in Seattle, WA?
It depends on size and placement.
Seattle requires a deck permit above 18 in, well below the common 30 in line.
Decks more than 36 in high count toward lot coverage.
Over 8 ft high, over 750 sq ft or with solid decking means a full addition/alteration permit.
Rules last checked by a person on October 19, 2026. Guidance only; confirm with Seattle before you build.
Check your exact lot
Setbacks depend on your zoning district, and a flood zone can change the permit answer. Enter your address to see both.
Permits a deck can need in Seattle
| Permit | When it applies |
|---|---|
| Building permit | Seattle requires a permit for decks more than 18 in above the ground, roof decks, and decks in or near critical areas. |
| Floodplain development permit | If the lot is in a FEMA special flood hazard area, all development there needs a permit. |
Neighborhood Residential (NR1, NR2, NR3)
| Front (decks over 18 in) | Not within 10 to 15 ft of the front line |
|---|---|
| Side (decks over 18 in) | Not within 3 to 5 ft of either side line |
| Rear (decks over 18 in) | Not within 5, 10 or 15 ft of the rear line, depending on units on the lot |
| Lot coverage | Decks over 36 in count toward the NR coverage cap |
Local details
- A full addition/alteration permit (not the simpler field-inspection permit) applies if the deck is over 8 ft high, uses beams 14 ft or longer, is a roof deck, has solid decking, or exceeds 750 sq ft.
- Call 811 at least a few days before you dig footings or post holes. Utility locating is free.
- HOA covenants and deed restrictions can be stricter than city rules. Check yours before you build.
How to apply
- Seattle Services Portal
- SDCI common projects
- SMC 23.44, Neighborhood Residential
- Phone: (206) 684-8600
Questions people ask
- When does a deck need a building permit in Seattle?
- Seattle requires a permit for decks more than 18 in above the ground, roof decks, and decks in or near critical areas. Decks 18 in or lower, on the ground and away from critical areas, don't need a permit.
- Where do I apply for a deck permit in Seattle?
- Apply through Seattle Services Portal, or call (206) 684-8600.
Sources
- Seattle SDCI, Decks. Checked 2026-10-19.
You need a permit to build a deck if it is: More than 18 inches above the ground; A roof deck; In an environmentally critical area.
- 44 CFR 59.1, definition of development (NFIP). Checked 2026-10-19.
Development means any man-made change to improved or unimproved real estate, including but not limited to buildings or other structures...
- 44 CFR 60.3, floodplain management criteria. Checked 2026-10-19.
Require permits for all proposed construction or other development in the community...