Kirkland, WA Environmental Rules: Flood Elevation Requirements (2026)

Kirkland's flood damage prevention chapter, KMC 21.56, sets the elevation floor for anything built or substantially improved inside a mapped special flood hazard area. Under KMC 21.56.090(1)(A), new construction and substantial improvement of a residential structure must have the lowest floor, including any basement, elevated one foot or more above base flood elevation (BFE), and mechanical equipment and utilities must be waterproofed or raised to that same one-foot freeboard. Any fully enclosed space below the lowest floor that could flood is either prohibited outright or must be built with flood vents: a minimum of two openings totaling at least one square inch of net area per square foot of enclosed space, with the bottom of every opening no higher than one foot above grade (21.56.090(1)(B)).

Attached garages with a slab below BFE need the same automatic-entry venting design. Nonresidential buildings get the same one-foot freeboard, or the ASCE 24 standard if it is greater, unless dry-floodproofed and certified by a licensed engineer or architect (21.56.090(2)). Critical facilities such as fire stations, hospitals, and police buildings must clear three feet above BFE or the 500-year flood elevation, whichever is higher (21.56.090(3)). Where no BFE has been published (an unnumbered A zone), the fallback is two feet above the highest adjacent grade.

None of this construction can start without a development permit under KMC 21.56.055, and an elevation certificate documenting the as-built lowest floor must reach the building official before vertical construction continues past the foundation. The building official administers the chapter, and the hearing examiner hears variance appeals under 21.56.075.