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Dry flood proofing is not generally recommended for buildings with a crawl space or basement, because these types of structures are susceptible to underseepage, which can result in significant "uplift" or buoyancy forces and create serious design problems. Generally, dry flood proofing should only be em- ployed on buildings constructed of concrete block or brick veneer on a wood frame. Weaker construc- tion materials, such as a wood frame, will fail at much lower water depths from hydrostatic forces. Even brick or concrete block walls should not be flood proofed above a height of three feet, due to the danger of structural failure from hydrostatic forces. Some waterproofing compounds cannot withstand significant water pressure or may deteriorate over time. For effective dry flood proofing, a good interior drainage system must be provided to collect the water that leaks through the sealant or sheeting and around the shields. These systems can range from small wet-vacs to a group of collection drains running to a central point from which water is removed by a sump pump. Property owners considering dry flood proofing should consult a professional engineer to analyze hydrostatic forces that can cause structural damage to walls and floors. Though dry flood proofing may seem simple, it is a sophisticated method that requires full understanding of the possible dangers stemming from poor planning, design, or installation. Most wall materials, except for some types of high-quality concrete, will leak unless special construction techniques are used. These techniques require a high level of workmanship if they are to be effective. The most effective method of sealing a brick faced wall would be to install a watertight seal behind the brick when the building is constructed. For flood proofing existing structures, the best way to seal a wall is to add an additional layer of brick with a seal "sandwiched" between the two layers. It is possible to apply a sealant to the outside of a brick or block wall, but any coating must be applied carefully. Cement or asphalt based coatings are the most effective materials for sealing a brick wall, while clear coatings such as epoxies and polyurethanes tend to be less effective. As a result. the aesthetic advantages of a brick wall are lost with the use of better sealant coatings. The difficulty and complexity of sealing a structure also depends on the type of foundation, since all structural joints. such as those where the walls meet foundations or slabs, require treatment. For very low flood levels, such as a few inches of water, a door can be flood proofed by installing a waterproof gasket and reinforcing the door jamb, hinge points, and latch or lockset and coating it with a waterproof paint or sealant. If there is a chance of higher flood levels, some type of shield will be needed. If the expanse across the door is three feet or greater, the shield will have to be constructed of heavy materials, such as heavy aluminum or steel plate. The resulting weight may require the shield to be permanently installed, using either a hinged or slide-in design. The frame for such an installation must be securely anchored into the structure. When windows are exposed to flooding, some form of protection is needed because standard plate glass cannot withstand flood forces. One solution is to brick up all or part of the window. It may also be possible to use glass block. instead of brick, to admit light. For normal-sized windows, shields can also be used. They should be made of materials such as heavy plexi-glas, aluminum, or framed exterior plywood. These can be screwed in place, or slid into pre- designed frame slots. Another alternative is to replace the glass with heavy plexi-glas; however, the win- dow must be sealed shut and waterproofed using water resistant caulking. 12