Updated Rules of Measurement for Height and Municipal Code Chapter 15-9 Flood Damage Controls

Beginning March 23, 2021 ontractors and sub-contractors for all new residential and commercial projects, additions, and equipment servicing the structures

The updated Flood Insurance Rate Maps for the Town of Hilton Head Island will become effective for flood insurance rating on March 23, 2021. In conjunction with the map adoption, the Town has updated the Land Management Ordinance (LMO) Section 16-10-102.C Rules of Measurement for Height and Municipal Code Chapter 15-9 Flood Damage Controls.

• Site plans, building plans, and elevation certificates shall use the NAVD88 datum as the elevation datum.


• For all properties in the Town of Hilton Head Island, maximum building height in each zoning district shall be measured from mean sea level starting at following elevations:
  1. Residential Construction - from 13' above mean sea level, and
  2. Nonresidential Construction - from 11' above mean sea level.
  
  
• The lowest floor elevation for all new construction and substantial improvements shall be as follows:
  
  1. Flood Zones AE, Shaded X and X:
  1. Residential structures must be constructed so that the lowest floor is elevated no lower than three (3) feet above the base flood elevation or thirteen (13) feet above mean sea level, whichever is higher.
  2. Nonresidential structures must be constructed so that the lowest floor is elevated no lower than two (2) feet above the base flood elevation or eleven (11) feet above mean sea level, whichever is higher.
  
  
  2. Flood Zones VE and Coastal A:
  1. All structures shall be elevated so that the bottom of the lowest horizontal supporting member is located no lower than three (3) feet above the base flood elevation level or thirteen (13) feet above mean sea level, whichever is higher.
  
  
  3. Flood Zone AO (areas of shallow flooding):
  1. Residential structures must be constructed so that the lowest floor is elevated to at least as high as the depth number specified on the Flood Insurance Rate Map, in feet, above the highest adjacent grade, or thirteen (13) feet above mean sea, whichever is higher.
  2. Nonresidential structures shall:
  1. Have the lowest floor elevated to at least as high as the depth number specified on the Flood Insurance Rate Map, in feet, above the highest adjacent grade or eleven (11) feet above mean sea level, whichever is higher, or
  2. Be completely floodproofed together with attendant utility and sanitary facilities to or above the depth number so that any space below that level 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.
  3. All structures on slopes must have drainage paths around them to guide water away from the structures.
  
  
  4. Manufactured homes shall be elevated on a permanent foundation such that the bottom of the frame of the manufactured home is three (3) feet above the base flood elevation or elevated to thirteen (13), whichever is higher and be securely anchored to an adequately anchored foundation system in accordance the South Carolina Code of State Regulations, Chapter 79, as amended.


• Electrical*, heating, ventilation, plumbing, air-conditioning equipment (including ductwork*) and other service facilities, i.e., water heaters, shall be elevated to or above the same elevation required for the lowest floor elevation as outlined above.
  
  *Electrical wiring systems and associated outlets and switches are permitted below the required elevation provided they conform to the provision of the electrical code for wet locations.
  
  ** Ductwork located below the height requirement must be designed so as to prevent water from entering or accumulating within the components during conditions of flooding and such design shall be certified by a South Carolina licensed engineer.

Questions?

Contact Shari Mendrck, Building Official at ShariM@hiltonheadislandsc.gov or 843-341-4687.