1206 & 1206 1%2 S Newhope St - Soils Report

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New building slabs-on-grade should be minimum 5 inches thick. reinforced with #4 re-bars at I 2-inches on-centers both ways. or equivalent. placed at mid-height of the slab. New slabs should be underlain by a 4 inch thick layer of clean sand. For moisture sensitive floor areas. the slabs should be underlain by minimum l0-mil polyethylene moisture barrier (such as Visqueen). Note: our recommendations are only minimum. The capillary break-/vapor barrier in accordance with the city requirements and or applicable Califomia Building code / Cal Creen Code will govem and should be followed. ln addition. the entire slab system including the capillary break/vapor barrier must be properly designed by the civil / structural design engineer of record (but not the geotechnical engineer) and be reviewed and approved by the city prior to construction- To reduce the potential for excessive cracking. new exterior concrete slabs-on-grade. if any. should be minimum 4 inches thick. provided with construction or weakened plane joints at frequent intervals (e. g.. every 6 feet or less). Provision of a 2-inch thick layer of crushed rock. gravel. or clean sand to be placed beneath the slabs and/or reinforcement. such as #3 rebars at l8 inches on-centers, or equivalent, placed at the mid-height of the slab should be considered. The subgrade soils lor the exterior slabs should be properly recompacted. Slab Subgrade Pre-Saturation Due to the low expansion polential of the on-site soils. presaturation of the slab subgrade earth materials is not considered necessary. However. sprinkling with water the slab subgrade earth materials, prior to concrete pour/placement of moisture barrier membrane should be considered. Other Recommendations fbr R educins Slab Crackins While not a geotechnical issue. the potential lbr slab cracking may also be reduced by caret'ul control of water/cement ratio and slump of concrete. The contractor should take appropriate curing precautions during the pouring of concrete in hot weather to reduce cracking of slabs. A slip sheet (or equivalent) can be utilized if grouted tile, marble tile. or other crack-sensitive floor covering is planned directly on concrete slabs. Scttlement The total settlement of I inch and a differential settlement of l/2 inch over a horizontal distance of 40 feet which are considered tolerable for residential buildings are anticipated and would occur during the construction stage. New Driveway The minimum section required by the govemmental agency can be used for a new driveway. if any. If there is no minimum requirement by the governmental agency. a 6-inch thick concrete slab. reinforced with #3 rebars at l8 inches on-centers, 6 in. thick asphalt concrete, or equivalent placed at mid-height ofslabs, over a 4-inch thick layer of aggregate base (AB) can be used. The Page 6 Nerv Exterior S labs-on-Grade