Washington enforces a statewide commercial building code that local jurisdictions must adopt and enforce. Local jurisdictions may amend the code if amendments meet state minimum standards, but they cannot opt out or adopt independent codes.
Seattle adopts the 2021 International Codes and Uniform Plumbing Code with both technical and administrative amendments. Local amendments impact building, fire, mechanical, plumbing, electrical, and stormwater requirements for commercial projects.
Seattle has scheduled a Stormwater Code and Manual update to take effect on July 1, 2026. The next statewide code revision, impacting building, fire, energy, mechanical, plumbing, and other codes, is delayed and not expected to be adopted until late 2026 at the earliest.