6101 23RD DR W NORPRO Geotech Report 2025-07-29

I June 3, 2011 Project No. T-6578 Perimeter foundations exposed to the weather should bear at a minimum depth of 18 inches below final exterior grades for frost protection. Interior foundations can be constructed at any convenient depth below the floor slab. I For short-term loads, such as wind and seismic, a one-third increase in this allowable capacity can be used. For designing foundations to resist lateral loads, a base friction coefficient of 0.35 can be used. Passive earth I pressures acting on the sides of the footings can also be considered. We recommend calculating this lateral resistance using an equivalent fluid weight of 350 pounds per cubic foot (pcf). We recommend not including the 111 upper 12 inches of soil in this computation because it can be affected by weather or disturbed by future grading activity. This value assumes the foundations will be constructed neat against competent native soils or backfilled with structural fill, as described in Section 5.2 of this report. The values recommended include a safety factor of I 1.5. The native silty sand to silty sand with gravel soils will be subject to disturbance from normal 'construction activity when in a wet condition. If disturbed, the soils will not be suitable for support and would need to be removed and replaced with new structural fill. To avoid soil disturbance, protection of bearing subgrade during wet weather with a layer of crushed rock or lean concrete mix should be considered. 5.5 Slab-on-Grade Floors I Slab-on-grade floors may be supported on subgrade prepared as recommended in Section 5.2 of this report. Immediately below the floor slabs, we recommend placing a four-inch thick capillary break layer of clean, free- draining, coarse sand or fine gravel that has less than three percent passing the No. 200 sieve. This material will reduce the potential for upward capillary movement of water through the underlying soil and subsequent wetting Iof the floor stabs. The capillary break layer will not prevent moisture intrusion through the slab caused by water vapor I transmission. Where moisture by vapor transmission is undesirable, such as covered floor areas, a common practice is to place a durable plastic membrane on the capillary break layer and then cover the membrane with a layer of clean sand or fine gravel to protect it from damage during construction, and aid in uniform curing of the I concrete slab. It should be noted that if the sand or gravel layer overlying the membrane is saturated prior to pouring the slab, it will be ineffective in assisting in uniform curing of the slab, and can actually serve as a water supply for moisture transmission through the slab and affecting floor coverings. Therefore, in our opinion, Icovering the membrane with a layer of sand or gravel should be avoided if floor slab construction occurs during the wet winter months and the layer cannot be effectively drained. We recommend floor designers and I contractors refer to the 2003 American Concrete Institute (ACI) Manual of Concrete Practice, Part 2, 302.1R-96, for further information regarding vapor barrier installation below slab-on-grade floors. I Other methods are available for preventing or reducing water vapor transmission through the slab. We recommend consulting with a building envelope specialist or contractor for additional assistance regarding this issue. I I Page No. 9 I