(A) (1) All new construction and substantial improvements of residential structures shall be elevated so that the top of the lowest floor level (including basement) is elevated to or above the design flood elevation.
(2) All new construction and substantial improvements of non-residential structures within Zone AE on the community FIRM may be floodproofed below DFE if they are designed so that below the design flood elevation the structure is watertight with walls substantially impermeable to the passage of water and with structural components having the capability of resisting hydrostatic and hydrodynamic loads and effects of buoyancy including attendant utilities and sanitary facilities.
(3) Where a non-residential structure is intended to be made watertight below the base flood level:
(a) A registered professional engineer or architect licensed in the state shall develop and/or review structural design, specifications, and plans for the construction, and shall certify that the design and methods of construction are in accordance with accepted standards of practice for meeting the applicable provisions of this chapter, including but not limited to Floodproofing Non-Residential Buildings (FEMA P-936) as published by the Federal Emergency Management Agency incorporated herein by reference; and
(b) A record of such certificates which includes the specific elevation (in relation to mean sea level) to which such structures are flood proofed shall be maintained with the Building Official.
(4) Enclosed areas below the design flood elevation, including foundation crawl space areas, shall be designed to automatically equalize hydrostatic and hydrodynamic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect licensed in the state or meet or exceed the following minimum criteria:
(a) A minimum of two openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided.
(b) The bottom of all openings shall be no higher than one foot above grade.
(c) Only the portions of openings that are below the base flood elevation (BFE) can be counted towards the required net open area.
(d) Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of flood waters.
(e) The area of the opening is the net clear opening calculated as the open area (excluding area of screening or other coverings that prohibit the free flow of water through the opening).
(f) Fill placed around foundation walls must be grated so that the grade inside the enclosed area is equal to or higher than the adjacent grade outside the building on at least one side of the building.
(5) In special flood hazard areas without base flood elevation data, new construction or substantial improvements of structures shall be elevated to at least two feet above the anticipated flood elevation during a base flood, as determined through an engineering analysis meeting the Federal Emergency Management Agency guidelines for flood insurance studies with the floodway to be established with no more than one-half foot rise.
(B) Specific standards in addition to general standards for VE and Coastal A zones. VE zones and Coastal A zones are areas designated as coastal high hazard areas. These areas have special flood hazards associated with wave wash, and therefore, the following provisions shall apply:
(1) All new construction and buildings that are substantially damaged or improved within VE and Coastal A zones are to be located landward of the reach of mean high tide.
(2) Provide that all new construction and substantial improvements in zone VE and Coastal A Zone, on the Charleston County FIRM, are elevated on pilings or columns so that:
(a) The bottom of the lowest horizontal structural member of the lowest floor (excluding the pilings or columns) is elevated to or above the design flood elevation; and
(b) The pile or column foundation and structure attached thereto is anchored to resist flotation, collapse and lateral movement due to the effects of wind and water loads acting simultaneously on all building components. Water loading values used shall be those associated with the base flood. Wind loading values used shall be those required by the International Building Code or International Residential Code as adopted and periodically amended by the state.
(c) A registered professional engineer or architect licensed in the state shall develop and/or review the structural design, specifications and plans for construction, and shall certify that the design and methods of construction are in accordance with accepted standards of practice for meeting the applicable provisions.
(3) New construction and substantial improvements shall have the space below the lowest floor either free of obstruction or constructed with non-supporting breakaway walls, open wood latticework, or insect screening intended to collapse under wind and water loads without causing collapse, displacement, or other structural damage to the elevated portion of the building or supporting foundation system. A breakaway wall shall be permitted only if a registered professional engineer or architect licensed in the state certifies that the designs proposed meet the following conditions:
(a) Breakaway wall collapse shall result from a water load less than that which would occur during the base flood; and
(b) The elevated portion of the building and supporting foundations system shall not be subject to collapse, displacement, or other structural damage due to the effects of wind and water loads acting simultaneously on all building components (structural and non-structural). Water loading values used shall be those associated with the base flood. Wind loading values used shall be those required by applicable state or local building standards.
(c) Electrical, mechanical and plumbing system components are not to be mounted on or penetrate through walls that are designed to break away under flood loads.
(4) There shall be no fill used as structural support. Non-compacted fill may be used around the perimeter of a building for landscaping/aesthetic purposes provided the fill will wash out from storm surge, thereby rendering the building free of obstruction prior to generating excessive loading forces, ramping effects, or wave deflection. The Building Official shall approve design plans for landscaping/aesthetic fill only after the applicant has provided an analysis by an engineer, architect, and/or soil scientist licensed in the state which demonstrates that the following factors have been fully considered:
(a) Particle composition of fill material does not have a tendency for excessive natural compaction;
(b) Volume and distribution of fill will not cause wave deflection to adjacent properties; and
(c) Slope of fill will not cause wave run-up or ramping.
(5) Man-made alteration of sand dunes and mangrove stands within zone VE and Coastal A Zones which would increase potential flood damage shall be prohibited.
(6) Pre-construction and as-built design and breakaway wall certifications, where applicable, shall be provided by registered professional engineers and/or architects licensed in the state for new and substantially improved structures in VE and Coastal A flood zones on the Charleston County FIRM. These certificates shall also be provided for all lateral additions to structures in the VE and Coastal A flood zones.
(7) Enclosed areas below the lowest floor shall be the minimum necessary to allow for parking of vehicles, limited storage, and access to the primary occupancy.
(8) Walls intended to break away under flood loads as specified shall have flood openings that meet the criteria in the general standards section for enclosed space below design flood elevation.
(9) Appurtenant features, defined as swimming pools, decks, gazebos, fences, and other features as determined by the Building Official as potentially causing an obstruction in the coastal high hazard area, must comply with the Federal Emergency Management Agency (FEMA) Technical Bulletin 5, Free of Obstruction Requirements, or any revisions thereto, incorporated herein by reference.
(10) Any and all other obstructions located in the VE Zone shall meet all applicable requirements of this chapter.
(C) Manufactured home and recreational vehicles additional specification standards in VE and Coastal A Zones.
(1) New or replacement manufactured homes (e.g., those designed to meet HUD standards) shall not be placed within property located in VE and Coastal A Zones.
(2) Existing manufactured homes in VE and Coastal A Zones may be permitted to remain as long as the structure complies with minimum health and safety standards and is anchored to resist flotation, collapse, lateral movement or debris impacts.
(3) The placement of a permanent recreational vehicle is prohibited in VE and Coastal A Zones.
(D) In Coastal A Zones, stem wall foundations supporting a floor system above and backfilled with soil or gravel to the underside of the floor system shall be permitted provided that the foundations are designed to account for wave action, debris impact, erosion and local scour. Where soils are susceptible to erosion and local scour, stem wall foundations shall have deep footings to account for the loss of soil. Stem walls are to be limited to a height of two feet above existing grade.
(Ord. 2016-14, passed 1-19-2017; Ord. 2020-11, passed 12-17-2020)