Flood Zone Descriptions for Charleston, SC

Floor Elevation Requirements:
The finished floor of all new and substantially improved residential structures must be elevated to a minimum of one foot above the base flood elevation indicated on the applicable flood insurance rate map. A flood elevation certificate indicating this elevation must be submitted prior to any building inspection except for a foundation inspection. This certificate must be of the latest version available.

Floodproofing Requirements:
Only non-residential structures in all "A" flood zones may be floodproofed to a minimum of one foot above the base flood elevation in lieu of elevating the finished floor to this elevation. A pre-construction (prior to the plans being released for permit) and an as-built (prior to final building inspection) floodproofing certificate must be completed by a South Carolina registered Architect and/or Professional Engineer for all floodproofed buildings. Construction plans for floodproofed buildings must also be sealed by a South Carolina registered Architect and/or Professional Engineer.

Equipment Elevation Requirements:
With the exception of one electrical outlet and one switch on a Ground Fault Interrupter (as required to meet the National Electrical Code), there may be no electrical wiring, plumbing fixtures, mechanical fixtures, other equipment or appliances, or ductwork located within new or substantially improved structures below one foot above the base flood elevation. Replacement HVAC systems in all "A" flood zones must be located either at or above the existing finished floor elevation or the base flood elevation, whichever is lower, unless the property is undergoing a "Substantial Improvement," in which case the HVAC system must be elevated to or above one foot above the base flood elevation.

Construction Materials Requirements:
Only Flood Resistant Materials per FEMA Technical Bulletin 2-93 (Class 4 or 5 materials) are permitted to be used below the base flood elevation unless the structure is a floodproofed non-residential structure.

Flood Control Vent Requirements:
Enclosed areas below the base flood elevation (e.g. garages, sheds, crawl spaces, etc.) must be provided with flood control vents located and sized in accordance with FEMA requirements (e.g. a minimum of two openings on different walls, located within a maximum of 12 inches of grade, sized at a minimum of one square inch per one square foot of enclosed area, with vents of the "always open" type). If these specifications are not met, a South Carolina registered Architect or Professional Engineer must certify in writing that the structure is designed to comply with FEMA requirements regarding equilization of hydrostatic and hydrodynamic forces.

Permitted Uses Below Base Flood Elevation:
Permitted uses below the base flood elevation are restricted to those necessary for building access, vehicle parking and limited storage of yard-related equipment.

Refer to the Charleston County Flood Damage and Prevention Ordinance (search FLOOD within the ordinance) for additional information.

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Lowest Horizontal Member Elevation:
The lowest horizontal structural member of all new and substantially improved structures must be elevated to a minimum of one foot above the base flood elevation indicated on the applicable flood insurance rate map. A flood elevation certificate indicating this elevation must be submitted prior to any building inspection except for a foundation inspection. This certificate must be of the latest version available.

Plan and Certificate Requirements:
Wall section and foundation plans for structures in "V" flood zones must be designed and sealed by a South Carolina Registered Professional Engineer. Plans must detail breakaway wall construction, foundation design and scour depth. If spread footings are used, the bottom of the footing must be a minimum of 12 inches below the anticipated scour depth at the structure location.

Pre-construction "V-Zone design" and "V-Zone Breakaway wall" certificates must be submitted with the construction plans for review. As-built "V-Zone design" and "V-Zone Breakaway wall" certificates must be submitted prior to a final building inspection. Obtain copies of these certificates from the Charleston County Building Services Department.

Equipment Elevation Requirements:
With the exception of one electrical outlet and one switch on a Ground Fault Interrupter (as required to meet the National Electrical Code), there may be no electrical wiring, plumbing fixtures, mechanical fixtures, other equipment or appliances, or ductwork located within new or substantially improved structures below one foot above the base flood elevation. Replacement HVAC systems in "V" flood zones must be located either at or above the existing finished floor elevation or the base flood elevation, whichever is lower, unless the property is undergoing a "Substantial Improvement," in which case the HVAC system must be elevated to or above one foot above the base flood elevation.

Construction Materials Requirements:
Only Flood Resistant Materials per FEMA Technical Bulletin 2-93 (Class 4 or 5 materials) are permitted to be used below the base flood elevation.

Permitted Uses Below the Flood Elevation:
Permitted uses below the base flood elevation are restricted to those necessary for building access, vehicle parking and limited storage of yard-related equipment.

Walls Below the Base Flood Elevation:
All walls below the base flood elevation must be designed and certified by a South Carolina registered Professional Engineer to break away at pressures between 10-20 pounds per square inch.

Fill Restrictions:
No fill is permitted to be used for structural purposes in "V" flood zones. Landscaping fill is only permitted if a South Carolina registered Professional Engineer certifies in writing that the fill will not cause wave run-up or deflection.

Obstructions Prohibited:
No obstructions are permitted below the base flood elevation within a structure. Obstructions not located within a structure (e.g. permanent planters, elevated swimming pools, elevated tennis courts, certain types of fences, etc.) are also not permitted unless a South Carolina registered Professional Engineer certifies in writing that the obstructions will not cause wave run-up or deflection.

Lateral Addition Requirements:
Construction plans for lateral additions to properties located in "V" flood zones must be sealed and provided with certifications by a South Carolina Registered Professional Engineer as indicated above. Pre-construction and As-built Design and Breakaway Wall Design certificates, as applicable, must be submitted for lateral additions in "V" Zones.

If the amount of work done to construct the addition plus any construction-related work permitted within the past five years from when the addition is permitted is less than 50% of the market value of the structure to which it is attached, the addition must be at a comparable or higher elevation than the structure to which it is being attached.

If the amount of work done to construct the addition plus any construction-related work permitted within the past five years from when the addition is permitted is 50% or more of the market value of the structure, contact the Building Services Department for assistance.

Refer to the Charleston County Flood Damage and Prevention Ordinance (search FLOOD within the ordinance) for additional information.

For properties located in unincorporated Charleston County, Awendaw, Kiawah Island, Meggett, Ravenel, Rockville and Seabrook Island, the Charleston County Building Services Department maintains copies of flood elevation certificates for all new construction and substantially improved structures.

If your structure was constructed in one of these jurisdictions since 1990, the Charleston County Building Services Department may have an elevation certificate on file for your structure. For structures where an elevation certificate is not available on file, a S.C. Registered Land Surveyor will need to survey the elevation of the structure and complete the flood elevation certificate form. Charleston County does not survey structures for the purpose of completing flood elevation certificates.