Wilmington, NC Environmental Rules: Flood Elevation Requirements (2026)

Sec. 18-660 of the floodplain management article applies once FEMA has published base flood elevation (BFE) data for a site. New construction and substantial improvements of residential structures, including manufactured homes, must have the lowest floor, including any basement, elevated to at least two feet above the BFE; that two-foot margin is the city's freeboard, which combines with the BFE to set what the ordinance defines as the regulatory flood protection elevation (Sec. 18-812). If a builder uses solid foundation perimeter walls to reach that elevation, the walls must include openings that let floodwaters move through instead of pooling against the foundation.

Nonresidential buildings, commercial and industrial structures, face the identical two-foot-above-BFE floor elevation, but Sec. 18-660(b) gives them an alternative: a structure in an A zone may be floodproofed rather than elevated if every area below the required elevation is watertight, with walls substantially impermeable to water and structural components engineered to resist hydrostatic and hydrodynamic loads and buoyancy. A registered professional engineer or architect must certify that the floodproofed design meets the standard, and that certification goes to the floodplain administrator under Sec. 18-646(b) before the city signs off.

Where no BFE has been published for a site, Sec. 18-663 falls back to a flat two feet above the highest adjacent grade. Compliance is checked twice: an elevation or floodproofing certificate is due within 21 days after the lowest floor is set, and a final as-built elevation certificate, with dated photographs, is required before the city issues a certificate of occupancy under Sec. 18-646(c) and (d).