Charleston, SC Environmental Rules: Flood Elevation Requirements (2026)
Key Facts
- Residential freeboard, new construction
- 2 feet above base flood elevation
- Residential freeboard, substantial improvement
- 1 foot above base flood elevation
- Non-residential option
- 2 ft elevation or certified flood-proofing
- Certifying professional
- Registered engineer or architect required
- Foundation ban effective date
- January 1, 2024, certain FEMA diagrams
- Administering officials
- Floodplain manager, chief building official
Summary
Charleston requires new residential construction in a special flood hazard area to elevate its lowest floor at least two feet above the base flood elevation, one foot higher than FEMA's minimum. City Code § 27-117(1) sets that freeboard standard, and non-residential buildings must either meet the same two-foot elevation or be certified flood-proofed by a licensed engineer or architect under § 27-117(2).
(1)Residential construction. New construction shall have the lowest floor, including basement, or the applicable structural member elevated at least two (2) feet above the level of base flood elevation prescribed for that zone. Substantial improvement of any residential structure shall have the lowest floor, including basement, or the applicable structural member elevated at least one (1) foot above the level of the base flood elevation prescribed for that zone.
Official source re-checked September 7, 2026: no newer edition of the code had been published (publisher’s edition: Code of Ordinances: Supplement 114 | Zoning: Supplement 25).
Full Breakdown
§ 27-117(1) turns that safety margin into a hard number for new residential construction: the lowest floor, including any basement, or the lowest structural member must sit at least two feet above the base flood elevation shown for that zone on the Charleston Flood Insurance Rate Map. A substantial improvement to an existing residential structure only needs one foot of freeboard above base flood elevation, a lower bar than new construction. § 27-116(a)(2) folds the freeboard into the general construction standard, requiring electrical, heating, plumbing, and HVAC equipment to be designed or located so floodwater cannot enter or accumulate during a base flood plus the applicable freeboard.
Beginning January 1, 2024, § 27-116(c) also bans several FEMA-diagrammed foundation types for new single-family dwellings citywide in the regulatory floodplain, on top of the elevation requirement, and the floodplain manager reviews elevation certificates to confirm the foundation type used matches what the ordinance allows.
Violations & Fines
Building below the required freeboard, or without the elevation or flood-proofing certification § 27-117 demands, is a misdemeanor under § 27-111: a conviction carries the punishment set in § 1-16, plus all costs and expenses of the case. The floodplain manager and chief building official can also withhold or revoke permits and certificates of occupancy, under §§ 27-112 and 27-113, until a registered engineer or architect certifies the required elevation or flood-proofing has been met.
Frequently Asked Questions
How much freeboard does Charleston require above base flood elevation?
Who certifies that a Charleston building meets the flood elevation rule?
What happens if a Charleston structure is built below the required elevation?
Sources & Official References
Other rules in Charleston
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Flood Elevation Requirements in Nearby Cities
How other cities in Charleston County handle flood elevation requirements.