Whatcom County requires a building permit for retaining walls over four feet, measured from the bottom of the footing, and for any wall supporting a surcharge like a slope or driveway. Taller walls need engineered plans. Drainage and setbacks matter on the county's bluffs.
Retaining walls in unincorporated Whatcom County follow the building code administered by Planning and Development Services. A wall four feet or less, measured from the bottom of the footing, and carrying no surcharge, is generally exempt from a building permit. Taller walls, or any wall loaded by a driveway, structure, or slope above it, need a permit and usually engineered plans stamped by a licensed engineer. Drainage behind the wall is critical in this rainy climate, and walls near marine bluffs, steep slopes, or Lake Whatcom can face added critical-areas review. Setbacks apply near property lines.
An unpermitted wall over four feet can draw a stop-work order, required engineering, fines, and potential removal. Walls diverting runoff onto a neighbor invite a civil claim.
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