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

030 defines base flood elevation (BFE) as the elevation to which floodwater is expected to rise during the flood having a one percent annual chance of occurring, and defines freeboard as the safety margin added above that computed flood level to compensate for unknown factors like wave action and urbanization runoff. 060(2)(a) turns that margin into a hard number for residential construction: new construction and substantial improvement of any residential structure must have the lowest floor, including any basement, elevated to a minimum of one foot or more above base flood elevation, with mechanical equipment and utilities waterproofed or elevated to the same one-foot minimum.

Where no BFE has been established for the site, in an unnumbered A zone, the code falls back to a floor elevation at least two feet above the highest adjacent grade. 060(2)(b) face the same one-foot floor requirement, or the ASCE 24 standard if it is stricter, unless the owner instead dry-floodproofs the structure to that height with a professional engineer's certification. 060(2)(c) requires their lowest floor to sit three feet or more above base flood elevation, or at the 500-year flood height, whichever is higher, with protected access routes to match.

Manufactured homes in zones A1-30, AH, and AE must also be elevated one foot or more above BFE on a permanent, anchored foundation. Applicants floodproofing rather than elevating are notified that their insurance rating is based on one foot below the floodproofed level, so extra freeboard directly lowers future premiums.