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

Section 18-52 sets Dorchester County's specific flood-construction standards for every zone where FEMA has published base flood elevation data (Zones A, AE, AH, AO, A1-30, V, and VE). Subsection (1) requires new residential construction and substantial improvements, including manufactured homes, to have the lowest floor elevated no lower than two feet above base flood elevation, two feet of freeboard above the federal minimum, and it flatly bans basements in these structures. If a builder elevates the home on solid perimeter foundation walls rather than piers, § 18-52(4) requires flood openings, at least two openings on different walls, with a combined net area of one square inch per square foot of enclosed area below the flood line, so hydrostatic pressure equalizes automatically during a flood rather than pushing against sealed walls.

Subsection (2) applies the same two-foot freeboard to commercial, industrial, and other non-residential structures, though those buildings may be floodproofed instead of elevated if a registered engineer or architect certifies the design and the county approves an annual maintenance and exercise plan. Manufactured homes get their own cross-reference in subsection (3): the lowest floor must clear base flood elevation by two feet and be anchored per the state Manufactured Housing Board's anchoring regulation, Section 40-29-10, with an engineering certification required once the chassis elevation exceeds 36 inches.

Compliance is verified by the local floodplain administrator before a certificate of occupancy issues, tied to the floodproofing and elevation certificate process described in § 18-33.