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• swelled less than 4 percent. We estimate the average Potential Vertical Rise (PVR) for interior <br />floor slabs on this site would be less than 2 inches. Isolated locations could have a PVR of <br />about 4 inches. )f the subgrade moisture does not increase under a floor slab, essentially no <br />movement would be expected. Floor slabs should be placed as high above adjacent exterior <br />grade as possible to create drainage flow away from buildings. We estimate that the modulus <br />of subgrade reaction for the compacted fill or native clay that is anticipated to make up the <br />subgrade is at least 100 psi/in, which can be used for slab design where high rack loads or slab <br />bearing equipment will be provided. <br />The following measures should be taken to reduce damage which could result from <br />movement should the underslab materials be subjected to moisture changes. <br />(1) Floor slabs should be separated from all bearing walls and columns with expansion joints <br />• which allow unrestrained vertical movement. On sites where low to non expansive soils <br />exist, or if inert fdls will be provided under the slab, the floor can be structurally tied <br />to the foundation for additional stability as required. Additional geotechnical study <br />should be undertaken for sites where this is desired. <br />(2) Floor slabs should not extend beneath exterior doors or over foundation grade beams, <br />unless saw cut or jointed to allow unrestrained movement. <br />(3) Floor slab control joints should be used to reduce damage due to shrinkage cracking. <br />Joints should be provided about 12 feet apart in both directions. The requirements for <br />slab reinforcement and thickness should be established by the designer based on <br />experience and the intended slab use. <br /> <br />25 <br />