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File: 218267 November 30, 2018 be overlapped by the basement wall waterproofing. Perforated collector pipes should be embedded within the drain rock around the perimeter of the slab and at 20 foot spacing(one-way) under the slab to carry any water which gathers within the drain rock to the back-of-wall drain discharge location. The need for any sand over the top of the vapor barrier should be determined by the slab designer or architect. Window Well and Access Well Drainage-Window Well and Access Well Drainage should be tight lined to the same sump pump used for under-slab and wall drainage. This sump should be located in the stairwell area for easy access, and may discharge into the area drain system. There should be a minimum 4 inch lip between the wells and the floor slab. A high water alarm should be provided in the sump. Consideration should be given to a backup generator. No downspouts should discharge into any window well or stairwell/depressed patio. Slabs-on-Grade The house floors should not consist of concrete slabs-on-grade (although the basement floor may consist of a mat slab— see above). This is due to the expansive nature of the site soils which would cause deformations in a conventional slab-on-grade. However,the driveway,any sidewalks or patios, and garage floor may consist of conventional concrete slabs-on-grade, though it should be expected. that some seasonal/post-construction shifting of such slabs may occur. We have provided guidelines to help reduce post-construction movements, however, it is nearly impossible to economically eliminate all shifting_ To help reduce cracking, we recommend slabs be a minimum of 5 inches thick and be nominally reinforced with #4 bars at 18 inches on center, each way. Slabs which are thinner or more lightly reinforced may experience undesirable cosmetic cracking. However, actual reinforcement and thickness should be determined by the structural engineer based upon anticipated usage and loading. In large non-interior slabs (e.g. patios, garage, etc.), score joints should be placed at a maximum of 10 feet on center. In sidewalks, score joints should be placed at a maximum of 5 feet on center. All slabs should be separated from adjacent improvements (e.g. footings, porches, columns, etc.) with expansion joints. Interior floor slabs will experience shrinkage cracking. These cosmetic cracks may be sealed with epoxy or other measures specified by the architect. It would be prudent(though not required)to underlay all slabs with at least 24 inches of non-expansive materials. This will help to reduce future expansive soil movements of the slabs. Slabs which are not underlain by this non-expansive material may undergo excessive seasonal shifting. All interior slabs (including garage slab) should be underlain by a rninimurn of 4 inches of clean 3/4 inch crushed drain rock. The drain rock should be covered by a vapor barrier which conforms to ASTM E1745-97 (e.g. Stego Wrap or an approved equivalent). The architect or structural engineer should determine if sand is required over the vapor barrier. 10