What happens if you cross the 50 percent threshold — elevation and construction requirements

From the Town's substantial improvement notice and Chapter 152. If a structure is substantially damaged or substantially improved, it must be brought into compliance with the Flood Damage Prevention Ordinance. AE ZONES: § 152.22(A) — new construction or substantial improvement of any residential building shall have the lowest floor, including basement, elevated no lower than the Design Flood Elevation. The DFE is defined at § 152.04 as "the elevation of the base flood plus two feet." For commercial properties only, dry floodproofing to the DFE is an option in AE Zones (§ 152.22(C), with engineer or architect certification), but not in Coastal A or VE Zones. COASTAL A AND VE ZONES: the bottom of the lowest horizontal structural member of both residential and commercial structures must be elevated to or above the DFE. EQUIPMENT: § 152.20(E) — electrical, heating, ventilation, plumbing, air conditioning and permanent/fixed generator equipment and other service facilities including ductwork shall not be located below the DFE in new construction and substantial improvement construction, except essential lighting and power circuits (with stated carve-outs for EV chargers, service disconnects, pool equipment filters and pumps, and outdoor faucets under conditions). MATERIALS: § 152.20(C) — only flood-resistant materials below the DFE. PLANS: for AE Zone structures requiring elevation or other structural work, plans must be prepared by a SC registered professional engineer or architect; for Coastal A and VE Zone structures, structural plans must be prepared by a SC registered professional engineer and submitted with V-Zone/Coastal A Zone Design and Breakaway Wall Design Certifications. ENCLOSURES: § 152.23(B) — for elevated buildings, enclosed areas below the DFE shall not exceed 299 square feet cumulatively and cannot be temperature controlled; § 152.23(A) requires at least two flood openings on two different walls totaling not less than one square inch per square foot of enclosed area, with the bottom of openings no higher than one foot above grade. § 152.22(R)/(§152.20(R)) restricts what may be kept in enclosures below the DFE. FOUNDATIONS: § 152.20(Q) — beginning July 1, 2024, certain foundation types (FEMA NFIP Flood Insurance Manual Appendix B Diagrams 1A, 1B, 2A, 2B, 3 and 4 for new detached single-family; 1A, 2A, 2B, 3 and 4 for new attached) are prohibited for new single-family foundations in the 100-year regulatory floodplain; this does not apply to garages, additions, conversions, substantially improved, substantially damaged, or nonresidential structures. NONCONVERSION AGREEMENT: § 152.23(D) — required for all new and substantially improved elevated buildings where the ground floor is below the DFE, recorded with the Charleston County ROD, with a recorded copy returned before a certificate of occupancy issues.