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Alternate Foundation Recommendations: An alternative deep foundation system to the drilled piers is a <br />) helical screw pile foundation system, The helical screw pile foundation system should be designed by a <br />qualified engineer, using industry standards and be installed by a licensed/certified installer. We strongly <br />recommend that at least one test pile be advanced at the site so that the torque versus depth relationships <br />can be established and the proper shaft and helix size and type can be determined. A representative of <br />this office should observe the helical pile installations. <br />Floor Slabs: We have assumed that the proposed structures will be constructed utilizing concrete slab-on- <br />grade floor systems. Due to the very high swell potential of the natural clays and claystone bedrock <br />materials, we strongly recommend that the client use a structural floor system over a crawlspace for the <br />lower levels of the structures. However, if the client is willing to accept the risk of significant differential <br />slab movement if the underlying clays or bedrock materials become wetted, then the slabs can be placed <br />on these soils provided [he special design precautions outlined below are closely followed. <br />The following measures should be taken to reduce the amount of damage, which could result from <br />movement should the underslab clays or claystone bedrock materials be subjected to moisture changes. <br />1) The floor slabs should be separated from all bearing walls, columns and their foundation supports <br />with a positive slip joint. We recommend the use of'h-inch thick cellotex or impregnated felt. <br />2) Interior non-bearing partition walls resting on the floor slabs should be provided with a slip joint, <br />~) preferably at the bottom, so that in the event the floor slab moves, this movement is not <br />transmitted to the upper structwe. This detail is also important for wallboard and doorframes <br />and is shown in Figure #8. <br />3) A minimum 6-inch gravel layer should be prodded beneath all floor slabs to act as a Capillary <br />break and to help distribute pressures. Ptior to placing the gravel, the excavation should be <br />shaped so that if water does get under the slab, it rril! flow to the low point of [he excavation. In <br />addition. any topsoil materials should be removed prior to placement of the underslab gravels or <br />fill materials. <br />4) The floor slabs should be provided with control joints placed a maximum of 12 feet on center in <br />each direction to help control shrinkage cracking. The location of the joints shotild be carefully <br />checked to assure that the natural, unavoidable cracking will be controlled. <br />5) The underslab soils should be kept as close as possible to their in-situ moisture content, <br />Excessive wetting or drying of these soils prior to placement of the floor slab could result in <br />difl'eren[ial movement after the slabs are conswaed. <br />6) It has been our experience that the risk of floor slab movement can be reduced somewhat by <br />removing at least 3 feet of the expansive materials and replacing them with a well compacted, <br />non-expansive fill. If this is done or if fills are required to bring the underslab soils to the desired <br />1 <br />JeL Number: 03-3838 14WCC, Lx. Page 3 <br />