How to Raise Your House Up-And Out of Harm's Way

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Release date: 
November 20, 1998
Release Number: 
1257-036

SAN ANTONIO, Texas -- If your home was damaged in the recent flooding and you are thinking about elevating the house to comply with floodplain regulations and to stay dry during the next flood, state and federal officials are offering some helpful information about the process you should know.

"We think homeowners will benefit from having as much information as possible before they launch their rebuilding efforts," said Ed Laundy, state coordinating officer with the Texas Division of Emergency Management.

Whatever you decide to do, check with local officials before you start any work rebuilding. Local ordinances and codes determine in large part what you can and cannot do - and what you should do.

What should you consider before elevating?

Before you decide to elevate your house to protect against future flooding, you should consider the following:

  • What level of flood protection do you want? Do you want to protect against the base flood (commonly called the 100-year flood), the 500-year flood, or some other level?
  • What kind of flooding would your house be subjected to? Take into account
  • the depth of flooding (even still floodwaters exert pressure on walls and floors)
  • the velocity of the floodwaters (how fast they move affects the damage potential)
  • how often you might expect flooding in your area (for example, a 100-year flood has a one percent chance of striking in any year)
  • the rate at which floodwaters rise and fall (this affects how much warning you may have)
  • how long the floodwaters will remain before they recede (the longer a house is exposed to floodwaters, the worse the damage)
  • the impact of floating debris on your house

Once you have weighed all these factors, you should consult with your local building authorities and contractor to discuss your options. Local jurisdictions may adopt more restrictive requirements than the National Flood Insurance Program.

When should you consider elevating your house?

If your house is in a special flood hazard zone (100-year floodplain) and you have received substantial damage (50 percent of your home's pre-flood market value) or are undertaking substantial improvements (costing in excess of 50 percent of your home's post-flood market value), you MUST either elevate your house, move it out of the floodplain or wet floodproof it.

If you live in a low- to moderate-risk area, you may still choose to elevate your home for added protection.

What does it mean to elevate a house?

Elevating a house means raising its lowest floor above the flood protection elevation (FPE), a level at which your chances of flooding are greatly diminished or eliminated. The FPE includes one additional foot of elevation to compensate for the uncertainties that exist in expected flood elevations. When a house has been elevated above that level, it still may be subject to flooding and face some risk of damage, but far less than before elevation.

How is a house elevated?

When a house is elevated, it is separated from its foundation, raised on hydraulic jacks and held up by temporary supports while a new or extended foundation is constructed below. The new foundation can be continuous walls or separate piers, posts, columns or pilings. The method varies if the foundation and the floor of the house are the same.

In areas where there is a low risk of wave action and high-velocity flow, the foundation is saved and existing walls extended, raising the floor level. In areas of high risk, open foundations are preferred because they let the floodwaters flow through, reducing the risk of structural failure. Open foundations are built with piers, posts, columns or pilings.

Masonry houses ...

Last Updated: 
July 16, 2012 - 18:46
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