Building permits in Seattle, WA

Short answer: In Seattle, permits are issued by Seattle Department of Construction and Inspections (SDCI); plumbing permits by Public Health – Seattle & King County; of the 6 common projects we checked, 1 always need a permit, 0 do not, and 5 depend on the details.

Permitting authority: Seattle Department of Construction and Inspections (SDCI); plumbing permits by Public Health – Seattle & King County. Rules differ in environmentally critical areas (steep slopes, wetlands, flood-prone areas). Plumbing and gas piping permits, including water heaters, are issued by Public Health – Seattle & King County, not SDCI.

Permit rules in Seattle
Project	Answer	Verified
Deck	Depends on your project No permit for platforms and walks less than 18 in above grade and not over a basement. Higher decks need a permit.	2026-10-19
Fence	Depends on your project No permit for fences under 8 ft with no concrete or masonry parts over 6 ft.	2026-10-19
Interior / bathroom remodel	Depends on your project No building permit for minor alterations costing $6,000 or less in any 6 months, or for finishes and cabinets. Plumbing work needs a Public …	2026-10-19
Roof replacement	Depends on your project No permit for re-roofing a one- or two-family home or townhouse if the building envelope is unchanged (other than equal or better insulation…	2026-10-19
Shed	Depends on your project No permit for a single-story detached shed with a roof footprint of 120 sq ft or less on a slab, pier blocks or soil, outside environmentall…	2026-10-19
Water heater replacement	Permit required Yes, since July 1, 2026. Public Health – Seattle & King County now requires a plumbing permit for every replacement water heater, including …	2026-10-19

Fee schedule: https://www.seattle.gov/construction-and-inspections/permits/permits-we-issue-(a-z)/re-roof-permit · 1 verified Seattle permit fee

All Washington cities · All cities · Permit guides

Not legal advice. Always confirm with your local building department. Rules change, and your parcel's zoning, HOA, historic district, floodplain or utility work can change the answer. We show the official source and the date we last checked it so you can verify for yourself.