King County, WA Permit Requirements: Renovation Permits (2026)

King County requires building permits for renovation work that goes beyond minor repairs and cosmetic changes. The county adopts the Washington State Building Code, which is based on the International Residential Code (IRC) with state amendments. Exempt work includes: painting, wallpapering, tiling, carpeting, flooring, cabinet replacement, and countertop installation that does not modify structural elements, plumbing, mechanical, or electrical systems. Work requiring permits includes: structural modifications (removing or adding walls, enlarging openings), all electrical work (new circuits, panel upgrades, outlets — must be performed by a licensed electrician in Washington), all plumbing work (fixture relocation, water heater replacement, sewer line work), HVAC installation or replacement, re-roofing (a re-roof permit is required), window or door replacement that changes the rough opening size, and any work adding habitable square footage. King County permits can be applied for online through MyBuildingPermit.com or at the Department of Local Services offices. Simple projects like water heater replacements or furnace changes may qualify for express permits. More complex renovations require plan review, typically taking 3–6 weeks. In critical areas (wetlands, streams, steep slopes), even interior renovations that increase the building footprint or value beyond 50% may trigger additional environmental review. Renovations in flood zones must comply with FEMA standards and King County's flood hazard regulations.