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

010. In AE and A1-30 zones, or other A zones where the BFE has been determined or can reasonably be obtained, new construction and substantial improvement of a residential structure must have the lowest floor, including any basement, elevated one foot or more above the base flood elevation, and mechanical, electrical and utility equipment must be waterproofed or elevated to that same one-foot freeboard. Where no BFE is available and cannot reasonably be obtained (an Unnumbered A zone), the lowest floor must instead sit at least two feet above the Highest Adjacent Grade.

5, with a registered engineer or architect certifying the design. 010(1)(b). Recreational vehicles avoid these elevation standards only if they stay under 180 days, remain licensed and ready for highway use on wheels with only quick-disconnect utility hookups, or otherwise meet the full manufactured-home standard. Any enclosed area below the elevated lowest floor used for parking, access or storage must have at least two flood vents totaling one square inch of net opening per square foot of enclosed area, with vent bottoms no higher than one foot above grade.