Skagit County, WA Environmental Rules: Flood Elevation Requirements (2026)

160(1)(a) sets the county's one-foot freeboard standard: new construction and substantial improvement of any residential structure must have the finished floor elevation of the lowest floor elevated one foot or more above the base flood elevation. Fully enclosed areas below that lowest floor that are subject to flooding cannot be occupied, and must be designed to automatically equalize hydrostatic flood forces on exterior walls by letting floodwater enter and exit freely. Absent an engineer- or architect-certified design, the code sets minimum venting criteria: at least two openings with a combined net area of not less than one square inch for every square foot of enclosed area subject to flooding, with the bottom of every opening no higher than one foot above finished grade; screens, louvers, or similar coverings are allowed only if they still permit floodwater to pass automatically.

150(6)(b). Nonresidential structures may instead be floodproofed watertight to one foot above base flood elevation, but must be certified by a Washington-licensed professional engineer or architect. 160(5).