Aiken County, SC Environmental Rules: Flood Elevation Requirements (2026)

Section 24-2.10.19 of the Aiken County zoning ordinance sets the specific elevation standards that apply once FEMA has provided base flood elevation data for a site. New construction or substantial improvement of any residential structure, including manufactured homes, must have its lowest floor, including any basement, elevated "no lower than one (1) foot above the base flood elevation (100-year flood elevation)." That one-foot cushion above the calculated 100-year flood level is the county's freeboard requirement. Where a builder uses solid foundation perimeter walls to achieve that elevation, the walls must include flood openings sized to let floodwaters flow through automatically rather than trap water against the foundation.

Nonresidential construction, meaning commercial, industrial, or other nonresidential buildings, faces the identical one-foot freeboard standard for its lowest floor, but Section 24-2.10.19(2) gives owners of nonresidential buildings in "A" zones an alternative: dry floodproofing. A structure can be floodproofed instead of elevated if all areas below the required elevation are watertight, with walls substantially impermeable to water and structural components able to resist hydrostatic and hydrodynamic loads and buoyancy. A registered professional engineer or architect must certify that the floodproofing meets that standard, and floodproofed structures must maintain an approved maintenance plan with an annual exercise verified to the floodplain administrator. No basements are permitted in nonresidential flood-zone construction.

Elevated buildings with an enclosed area below the lowest floor, used only for parking, building access, or limited storage, must include at least two openings totaling one square inch of net open area per square foot of enclosed space, with the bottom of each opening no higher than one foot above the adjacent grade, so hydrostatic pressure equalizes automatically during flooding.