King County, WA Permit Requirements: Shed & Outbuilding Permits (2026)

Under the Washington State Building Code as adopted by King County, one-story detached accessory structures used for storage with a floor area of 200 square feet or less are exempt from building permits when accessory to a residential property. Exempt sheds must not include habitable space, plumbing, or electrical systems. Even exempt sheds must comply with King County zoning setback requirements under KCC Title 21A — typically 5 feet from side and rear property lines in most residential zones, though setbacks vary by zone. Sheds exceeding 200 square feet require a residential accessory building permit from King County's Department of Local Services. The permit application can be submitted through MyBuildingPermit.com. Plans must show structural details, setback compliance, and lot coverage calculations. In rural zones, agricultural buildings may have different exemption thresholds. King County's critical areas regulations may affect shed placement — sheds cannot be placed within wetland buffers, stream buffers, or on steep slopes without additional review. In flood hazard areas, sheds may need to be elevated or anchored. The Pacific Northwest's heavy rainfall makes proper foundation and drainage important for shed longevity — gravel pads and proper grading are recommended even for exempt structures.