Auburn, WA Fence Regulations: Retaining Walls (2026)

Auburn adopts IRC R105.2 through the Washington State Building Code. Retaining walls over 4 feet in height measured from the bottom of the footing to the top of the wall require a building permit and engineered design stamped by a Washington-licensed engineer. Walls 4 feet or less are permit-exempt if not supporting a surcharge (driveway, structure, or sloped fill above). Combined walls where a fence sits on top of the wall are treated as a single system: if the retaining portion alone exceeds 4 feet, the entire assembly requires a permit. In Auburn's hillside neighborhoods such as Lea Hill, Lakeland Hills, and West Hill, steep slope overlays and geologically hazardous areas trigger Critical Areas review under ACC 16.10, often requiring geotechnical reports even for shorter walls. Walls near the Green River floodplain require floodplain development permits. Terraced walls must have separation between tiers at least equal to the height of the lower wall to qualify as independent structures rather than one effective wall. Permits apply through the Auburn Permit Center.