Lewis County, WA Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Freeboard
- 2 ft above base flood elevation
- Residential lowest floor
- must reach flood protection elevation
- Nonresidential option
- floodproof instead of elevate
- Manufactured homes
- need permanent, anchored foundation
- Critical facilities
- 3+ ft above 100-year flood
- Violations
- up to $1,000 penalty per day
Summary
In unincorporated Lewis County's special flood hazard areas, new construction and substantial improvements must be elevated to the flood protection elevation, which LCC § 15.35.260 sets at the base flood elevation plus two feet of freeboard. Residential structures must raise the lowest floor, including any basement, to that height, while nonresidential buildings may floodproof to the same level instead.
"Freeboard" means an additional height requirement above the base flood elevation (BFE) that provides a margin of safety against extraordinary or unknown risks. This protects structures from waves, debris or unpredictable hazards that accompany the base flood. ... In order to account for the impacts of future development on flood depths, and in order to ensure the least expensive insurance rates for floodplain occupants, all development within special flood hazard areas which requires elevation or floodproofing shall be elevated or floodproofed to or above the flood protection elevation (base flood elevation plus two feet of freeboard). ... New construction on existing parcels, additions, and substantial improvement of any residential structure shall have the lowest floor, including basement, elevated to the flood protection elevation.
Full Breakdown
040 defines freeboard as an additional height requirement above the base flood elevation that provides a margin of safety against extraordinary or unknown risks, protecting structures from waves, debris, or unpredictable hazards accompanying the base flood. 260 turns that margin into a number: the flood protection elevation is the base flood elevation plus two feet of freeboard, and any development within a special flood hazard area that requires elevation or floodproofing must reach it. 270(1) requires the lowest floor, including any basement, of new construction, additions, and substantially improved structures to be elevated to the flood protection elevation; any fully enclosed area below that floor must either be prohibited or fitted with flood vents meeting a one-square-inch-per-square-foot opening ratio, with the lowest opening no higher than one foot above grade.
280: elevate to the flood protection elevation, or floodproof the structure watertight below that level with engineer or architect certification, though applicants are warned that a floodproofed building's insurance rating is calculated as if it sat one foot lower. 290. 300 requires their lowest floor at least three feet above the 100-year flood level.
Violations & Fines
Failing to elevate a structure to the required flood protection elevation is a violation of Chapter 15.35, enforceable under § 15.35.180 with a civil penalty of up to $1,000 per day. Beyond the fine, § 15.35.280(5) warns that a nonresidential building floodproofed rather than elevated is insured as if it were built one foot below the floodproofed level, raising the owner's flood insurance premium regardless of any penalty assessed.
Frequently Asked Questions
What is 'freeboard' under Lewis County's flood rules?
How high above the base flood elevation must I build?
Can a commercial building be floodproofed instead of elevated?
Do manufactured homes have to meet the same elevation rule?
Sources & Official References
Other rules in Lewis County
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