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<br />. Single and two story residential structures without basements, framed with. wood with a <br />partial brick or masonry siding, may float at depths of water less than 3 feet above the first <br />floor. <br /> <br />. Single and two story residential structures without basements, constructed of brick or <br />masonry with slab-on-grade may fail by buckling of the floor slab at depths of water of <br />about 3 feet. <br /> <br />. Baseme,:,ts in single story brick or masonry structures may fail by flotation or buckling of <br />the floor slab at depths of 4 feet above the basement floor if the soil becomes saturated. <br />The validity of the assumption of soil saturation depends upon the duration of flooding, <br />the type of soil, and the type of drainage system. Long duration flooding, permeable soil, <br />and the absence of any drainage system around the walls or floor are all conducive to <br />causing saturated conditions. <br /> <br />. Commercial and industrial structures are often constructed to take greater forces than <br />residential structures and consequently can generally be expected to withstand greater <br />hydrostatic pressures. Six feet of head is not unreasonable for many structures to <br />effectively resist and it could be more. <br /> <br />Recent structural tests on a brick veneer wall (backed with wood framing) showed the wall <br />failed with a head of less than 3 feet (4). Other analyses (1) on the design of basements for new <br />structures recommended that water be allowed to enter the basement should it reach the <br />basement window (about 5 feet above the basement floor). These analyses point to the <br />limitations and potential hazards of keeping water out of residential type structures. <br /> <br />Costs <br />Base costs to provide temporary or permanent closures are the cost of the closures <br />themselves and the cost of a sewer gate valve to prevent sewer backup. The cost of the closures <br />depends principally upon the type closure selected. Only one sewer valve is generally required. <br />An Engineer's estimate was made to provide these base cost items for a single or two story brick <br />or masonry structure without basement. These costs are tabulated in Table 3-1. The estimated <br />annual cost as a percentage of structure value is 0.34 percent. <br /> <br />15 <br />