North Charleston, SC Environmental Rules: Flood Elevation Requirements (2026)

Sec. 5-409(b)(1) provides that new construction and substantial improvement of any residential structure, including manufactured homes, shall have the lowest floor elevated no lower than two feet above the base flood elevation, that no basements are permitted, and that if solid foundation perimeter walls are used to elevate the structure, flood openings sufficient to automatically equalize hydrostatic flood forces must be provided. Sec. 5-409(b)(2) applies the same two-foot-above-BFE floor elevation to commercial, industrial, and other non-residential structures, but allows structures in A-zones to be floodproofed instead, watertight with walls substantially impermeable to water, provided a registered engineer or architect certifies compliance and the owner maintains an approved floodproofing maintenance plan with an annual exercise.

Sec. 5-407 defines freeboard as a factor of safety usually expressed in feet above a flood level for purposes of floodplain management that compensates for unknowns such as wave action, bridge openings, and the hydrological effect of watershed urbanization. In coastal high hazard V-zones, Sec. 5-409(f)(2) requires new construction to be elevated so the bottom of the lowest supporting horizontal structural member, excluding pilings, sits no lower than two feet above the base flood elevation. In AO-zone shallow flooding areas, Sec. 5-409(e)(1) requires the lowest floor at the higher of the flood map's depth number above the highest adjacent grade, or three feet if no depth number is shown, plus at least two feet above the nearest base flood elevation.

A narrow exception in Sec. 5-409(b)(9) lets a swimming pool's utility equipment room sit below the BFE only if the building itself cannot reach the BFE and the accessory-structure and anchoring conditions of Sec. 5-409(b)(8) are met.