Flooding, and the damage it causes building structures and home foundations, has become a greater problem today than in the past. Part of the problem can be attributed to the fact that more homes and commercial buildings are being built in areas prone to flooding. Areas once believed “safe” from all but the most severe flooding have experienced multiple floods in the past decade or two. It was once considered “safe” to build outside the 100 year flood plain but residential and commercial building owners realize that conditions change. The 100 year flood plain has been expanded to account for frequent floods in various areas. In addition, excessive pumping of water from underground reservoirs has resulted in ground subsidence and contributed significantly to the expansion of the 100 year flood plain. And coastal areas of the United States have been hit my monster hurricanes and their flooding in the past decade.
According to The Federal Emergency Management Agency (FEMA), flooding damage costs – home foundation problems, building structural damage, and displacement – are greatest in New York, Pennsylvania, Iowa, Illinois, Missouri, Oregon, California, Colorado, Louisiana, and Texas with average flood damage loses between $197,000,000 – $682,000,000 annually. To better understand the areas at risk a new mapping technique is being used by communities across the United States. Lidar is a new field of light detection and ranging using lasers. From an airplane it can map the ground with great precision. The concept is similar to submarine sonar probes of the ocean depths. This technology can collect 20,000 data points per second and yield highly accurate maps of elevation in a fraction of the time and cost.
FEMA has published a guide called “Homeowner’s Guide to Retrofitting: Six Ways to Protect Your House from Flooding” that addresses the problem of homes and commercial structures that lie in flood prone areas. The publication suggests elevating houses to a height which is at or above the Flood Protection Elevation (FPE). The FPE is defined as a height that will only be flooded by the most severe floods or a 500 year flood plain (once every 500 years). FEMA has outlined three techniques that can be used to raise a home and they can be used on both pier and beam and slab on grade concrete foundations. The first technique involves extending the walls of the home or structure upward and raising the lowest floor. With this technique the house has “grown” upward and the vacant space between the ground and the lowest floor can be flooded without any significant damage to the house. This technique works best with pier and beam foundations.
The second technique involves building a new second story on top of the existing one story structure and converting the ground floor into storage space or garage space. Any future flooding will create much less damage. This technique will work with both pier and beam and slab on grade foundations. The third technique involves lifting the entire house, including foundation, with hydraulic jacks and I-beams. This technique works very well with slab on grade foundations but can also be used with pier and beam. Trenches and tunnels will have to be dug under concrete slabs to allow access for the lifting equipment.
There are number of reasons homeowners and commercial property owners would want to elevate their property. Obviously they want to avoid future flooding damage to buildings, contents, and home foundations. In addition, after one or more floods an insurance company may refuse to renew its coverage for an entire area. And in some communities property elevation is mandatory if the property owner has suffered flood damage equal to or greater than fifty percent of the value of the structure and wishes to get permits to rebuild.
Source by Martin Dawson