Elevating your Home to Protect Against Flooding

Floods September 21, 2012|Print


Raising your home above the base flood elevation is one option you can take to reduce flood and wave action damage.

Raised houses, an old strategy to address flooding, exists throughout the world. Photo: University of Nebraska-Lincoln, Shirley Niemeyer

Elevating or raising the structure above the base flood elevation means the lowest living floor space is above the projected water levels. The base flood elevation (BFE) means that elevation or level has a 1 percent chance of being equal to or exceeded by floodwaters in any year. Note that FEMA indicates vulnerable structures should be elevated above the floodwaters associated with a 100-year storm event (1 percent chance of being flooded in any one year) or the "Base Flood." Flood Insurance Rate Map (FIRM) maps depict the required Base Flood Elevation ("BFE"), the 500-year floodplain and the flood insurance zones. The information can be found at http://www.fema.gov/hazard/map/firm.shtm.


Check with housing inspectors, code enforcement, and building or zoning offices that govern your area to find out what can be done or if elevation is possible. Restrictions may be in place concerning elevating the home. Contact a qualified contractor, design professional, or engineer with an understanding of the elevation process and experience with these construction and mitigation techniques. A new supporting foundation will be needed. An inspection of the house is also needed to ensure that the structure is solid enough to withstand the work.

Contact your insurance agency for information about how elevating the home may influence your insurance rates. Elevation of the home may reduce the premium based in part on how high the house is elevated. A cost-benefit analysis should be performed to optimize the level of elevation.

Contact the Federal Emergency Management Agency or your state or county Emergency Management Agency office for more information and for information about the National Flood Insurance Program and its requirements.

The Process

Cribbing - termporary frame used to elevate the home. Illustration courtesy of Purdue University, Kimberly Batta.

Before moving the house, the structure is secured to reduce structural damage and is disconnected from the foundation and utilities. It is then very slowly raised upward and placed on a temporary framework called cribbing. The new foundation may be pilings. In some cases, piers or columns are used. Foundation walls may be restricted in some A and in V flood zones. If foundation walls are allowed, they must have openings to allow the floodwaters to enter under the house and to recede, and to be able to withstand the pressure forces. Breakaway wall sections are sometimes used if allowed.

Fill dirt and the base for the foundation must meet local or area codes. Fill dirt must be adequately prepared and packed. The new area below the home should not be used for living space.

Elevated home. Photo courtesy of University of Nebraska-Lincoln, Shirley Niemeyer.

 

Open foundation with posts or columns. Photo: FEMA, Robert Harris.

More Resources to Protect Against Flooding

Federal Emergency Management Agency. Above the Flood: Elevating Your Floodprone House. FEMA publication 347.

Federal Emergency Management Agency. Homeowner's Guide to Retrofitting: Six Ways to Protect Your House from Flooding, Chapter 5.

Federal Emergency Management Agency. Protect Your Property from Flooding

Federal Emergency Management Agency. Home Builders Guide to Coastal Construction. Lowest Floor Elevation. Technical Fact Sheet 4.

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