An elevation is the process of raising a structure above the base flood elevation, or the flood level of a 100-year floodplain. Elevations allow water to flow freely below the structure thereby protecting the structure itself and its contents. Elevations are particularly appropriate for smaller wood frame buildings and in floodplain areas where flood depths do not exceed six feet and velocities are slow.
Elevating a building is generally less expensive than relocating the structure and will cause less disruption to a neighborhood. If the amount of elevation required for flood protection is low, then the building many only need to be raised 2-3 feet. When a greater degree of flood protection is necessary the building may be raised 8 feet and the lower areas can be wet flood proofed and used as a storage area or as a garage. Elevating with change the appearance of the structure. For instance, raising a house two feet will add three more steps in order to get to the front door. It is also important to keep in mind that the building may be isolated and without utilities during a flood period because the surrounding yard and roads are likely to be flooded.
Building elevation can be expensive depending on the structure. Raising a wood frame house on a crawlspace can cost as little as $5,000 when the owner does much of the work. A structure with brick walls on a slab foundation can cost as much as $25,000. FEMA offers a cost-share elevation program. For information, see FEMA Elevation Grant Program.
"Flood Hazard Mitigation in Northeastern Illinois: A Guidebook for Local Officials," Northeastern Illinois Planning Commission and French & Associates, Ltd., 1995.