Washington County, MD Environmental Rules: Flood Elevation Requirements (2026)

0 as the base flood elevation plus one foot of freeboard, building a mandatory one-foot safety margin above FEMA's mapped base flood elevation into every county elevation requirement. 3(A)(1) applies that definition directly to housing: new residential structures and residential portions of mixed-use structures, along with substantial improvements to existing residential structures (including repair of substantial damage), must have their lowest floor elevated to or above the flood protection elevation. 3(A)(2) sets an alternate standard: the lowest floor, including any basement, must sit at least as high above the highest adjacent grade as the depth number shown on the FIRM plus one foot, or at least three feet if the map shows no depth number.

3(C): it may be used only for vehicle parking, building access, crawl or underfloor space, or limited storage, must use flood damage-resistant materials, and must have at least two flood openings on different exterior walls sized to provide at least one square inch of net opening per square foot of enclosed area, or engineered openings certified by a licensed professional engineer. 5's engineering-analysis requirements.