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J.. H. KLEINFELDER & ASSOCIATES <br /> _ File No. 20-2925-01 <br /> June 16, 1987 <br /> Page 5 <br /> Lateral Forces <br /> Resistance to lateral forces can be provided either by friction between the base <br /> of the foundation and the soil, or by passive pressure of the sides of the footings <br /> against the soil. The recommended friction factor is 0.4. The recommended passive <br /> - soil pressure is an equivalent fluid pressure of 350 pounds per square foot per foot of <br /> depth. <br /> Li <br /> Floor Slabs <br /> We recommend that floor slabs be underlain by a minimum of 6 inches of <br /> recompacted native soil or Engineered Fill. The recommended minimum degree of <br /> compaction is 90 percent of the maximum dry density as obtained from the ASTM <br /> D-1557 test procedure at a moisture content near optimum. Due to the relatively <br /> impermeable cemented near-surface soils, we recommend the floor slabs be underlain by <br /> - a capillary moisture break such as provided by an approximate 4-inch layer of gravel <br /> or coarse sand. In areas to receive moisture-sensitive floor coverings, we recommend <br /> that the gravel or coarse sand be covered by a moistureproofing membrane such as <br /> "Moiststop," or equivalent, to act as a vapor barrier. Care should be exercised to <br /> avoid tearing, ripping, or displacing the membrane during construction. If the <br /> membrane becomes torn or disturbed, it should be removed and patched, or thoroughly <br /> replaced. The membrane should, in turn, be covered with approximately 1 inch of <br /> moist sand to protect it during construction and aid in curing the concrete. <br /> For the structures planned, we recommend that floor slabs be a minimum of 4 <br /> inches in thickness, and reinforced with at least wire mesh placed at midpoint in the <br /> slab. The actual floor slab thickness and reinforcing should be provided by the <br /> structural engineer. <br />