Shed permit rules in Seattle, WA — also referred to as storage shed, backyard shed, or accessory building regulations — set size limits, setbacks, and when a building permit is required.
One-story detached accessory structures (sheds, playhouses) under 200 sq ft do not require a building permit under Washington State Building Code (IRC). Structures in Environmentally Critical Areas require additional ECA review regardless of size. Setback and zoning requirements apply.
In Seattle, a one-story detached accessory building (shed, greenhouse, playhouse) does not require a building permit if the projected roof area is less than 120 square feet, the building is on a slab, pier blocks, or soil foundation, is not attached to another building, is not in an Environmentally Critical Area, and is used only for storage, gardening, or similar purposes. Maximum height is 12 feet. Sheds must comply with lot coverage limits: 35% in NR zones for lots 5,000+ sq ft, or 1,000 sq ft plus 15% for smaller lots. Setbacks mirror garages: 20 feet from front property line, 5 feet from side. Sheds can go in the rear 25 feet or rear 20% of lot depth (whichever is less). Sheds over 750 sq ft, in ECAs, or with beams spanning 14+ ft require a full permit. Electrical service requires a separate electrical permit. Converting a shed to living space requires a Construction Addition/Alteration Permit.
Oversized unpermitted shed: SDCI violation. Living in a shed: code violation requiring full permit compliance.
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Side-by-side rule comparisons with other cities in King County.
See how other cities in King County handle shed rules.
See how Seattle's shed rules rules stack up against other locations.
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