Elevation provides the best protection from flood damage short of relocating the house to an area that is less prone to flooding.
Next to demolition and relocation, elevation is the method most favored by the Federal Emergency Management Agency (FEMA) for reducing flood damage to a building. New construction in flood-hazard areas must have the lowest floor at or above the level of the base (100-year) flood, called the Base Flood Elevation (BFE) on the Flood Insurance Rate Map (FIRM) or, the level indicated on flood recovery maps when they have been adopted by the community for regulatory purposes. Nonresidential structures can meet the elevation requirement by dry floodproofing; residential structures do not have this alternative -- they must be elevated.
Raising a structure does not remove it from the special flood hazard area (SFHA); therefore, it does not exempt the owner or the mortgage company from flood-insurance mandates. If the ground level adjacent to the structure has been raised above flood level by importing fill material or altering the terrain, the owner may file for removal of the property from the SFHA. The current fee for removal on this basis is $425 for a single lot; a survey and certification of compaction are required. Some Louisiana communities restrict the use of fill; fill may not be used to support an elevated building in V zones.
Elevation is required for buildings that have been substantially damaged and buildings that are being substantially renovated. When a building is substantially improved by addition of a room, the addition, and sometimes the entire structure, must meet current elevation requirements.
Substantial means the cost of improvements or repairs, as a percentage of the market value of the structure before improvement or before damage, exceeds some threshold value. The maximum threshold value allowed by FEMA is 50%; in some Louisiana communities local governments have lowered the threshold to 40% or 25%. The local permit office can tell you what the substantial damage threshold is in your community.
Elevating a building to prevent flood damage doesn't always mean picking up the entire structure. Explore these Three Ways to Get the Floor Up.
The Rising Above the Flood brochure explains the slab-elevation process as it was demonstrated in the Amite River Basin near Baton Rouge. This project was also documented in the Above the Flood video. Simple diagrams that compare elevating a slab home by removing it from the slab and by raising the slab are shown on this Elevation Diagrams page.
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