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Soil Type Permeable soils. such as sand, are those that allow groundwater to flow freely. If a building has a basement and is located on permeable soil, flood proofing measures involving sealants and closures are usually ineffective because the permeable soil will allow groundwater to increase forces along the base- ment walls. causing seepage and/or structural damage to the building. Buildings with crawl spaces will have seepage problems while those with concrete slabs will experience uplift when constructed on per- meable soils. Water will pass under floodwalls and levees constructed on permeable soil unless expen- sive seepage control measures are included as part of the flood proofing. Other problems with soil that is saturated with flood waters also need to be considered. If a building is located on unconsolidated soil. wetting of the soil may cause uneven (differential) settlement. The building may then be damaged by inadequate support and pulling or bending forces. Some soils may expand when exposed to floodwater and cause pushing forces against basement walls and floors. Thus, serious damage can occur even though floodwaters do not enter the structures. To determine if a building is sited on permeable or other flood impacted soil, contact the local office of the SCS or a local geotechnical engineering firm. Techni- cal expertise is required to resolve problems associated with adverse soil conditions. ~ BUILDING CH'RACTERISTlCS ~ Building Foundation There are three basic types of foundations for structures, which may be utilized individually or in various combinations. They are slab-on-grade, crawl space with the building supported on foundation walls. and basements with poured concrete walls and floors or masonary walls and poured concrete floors. Each type of foundation has its own advantages and limitations when flood proofing measures are being evaluated. All types of flood proofing can be considered for slab-on-grade and crawl space foundations. However, the crawl space foundation generally provides for more economical elevation and relocation flood proofing measures. Buildings with basement foundations often require more involved flood proof- ing measures and are not recommended for some types of flood proofing. Building Construction Most buildings are constructed of concrete and masonry or wood. However. other materials such as alu- minum, vinyl, and fiberglass are also used. Combinations of these materials may be used in the con- struction of a single building. Thus. the suitability of applying a specific flood proofing measure can be difficult to assess. Concrete and masonry construction can be considered for all types of flood proofing measures. whereas, other materials may not be structurally sound. When classifying building construc- tion as concrete and masonry, it is important that all walls and foundations be constructed of this mate- rial. Otherwise, there may be a weak link in the flood proofing measure resulting in potential for failure. For general consideration of flood proofing measures, all construction should be classified with wood material unless all walls and foundations are concrete and masonry. Building Condition Building condition may not be easy to evaluate as many structural defects are not readily apparent. However, careful inspection of the property should provide for a classification of "excellent to good" or "fair to pOOL" This classification is only for the reconnaissance phase of selecting an appropriate flood proofing measure(s). More in-depth planning and design may alter the initial judgment regarding building condition and eliminate consideration of some flood proofing measures. 16