2016-00571 - addition / remodel - Laserfiche WebLink

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Project Number: 016-0019-5391 Page 3 To achieve the capacity, we anticipate the helixes to bear within the Stiff sandy lean clay below 25 feet at the exptored location. We estimate the anchor lengths to be on the order of 20 to 25 feet. An experienced contractor should be consulted for specific details and installation. Site drainage should be maintained during and after construction. The site should be adequately graded to provide surface runoff away from the proposed building in all directions so surface water does not collect within the excavation bottom or below the spread footing foundations. In addition,the surface of the fill surrounding the buildings should be capped with cohesive soils to minimize water migration betow the building. To avoid undermining the existing foundations,the excavation should not be performed within the zone extending downward at a 45 degree angle from the bottom of the existing footings. If excavation in this zone cannot be avoided,the existing footings should be underpinned during the excavation procedure. In addition, care should be exercised during compaction adjacent to the existing building so as not to damage the existing structure. It should be pointed out that rigid structural connections between the new addition and the existing building are not ideal. Because of the nature of the foundations and supporting materials, some vertical movement between the existing and the new structure should be expected. These movements will include both foundation settlement and elastic movement of the foundation material and structural elements. Therefore, we recommend that appropriate joints be installed between the new and the existing structures to provide tolerance for vertical movement. All perimeter foundations in heated building space should be placed at a minimum depth of 42 inches below exterior grades for frost protection. Interior footings may be placed at any convenient depth below the floor slab. In unheated areas where deeper frost penetration may occur, we recommend that the foundations have a minimum soil cover of 60 inches for frost protection. The floor slab should be designed to be structurally supported on the building foundation system. We recommend that a minimum 4-inch thick, free-draining granular layer be placed under the floor slabs. This layer should consist of uniformly-graded sand or gravel with less than 5 percent passing the#200 sieve. In addition to facilitating fine grading for easier slab construction,the granular layer provides a capillary break to minimize moisture transmission from the subgrade to the floor slab. Backfill placed behind foundation walls in the basement area will exert lateral loads against these walls. The lateral loads could be minimized if free-draining granular soil is used as backfill immediately against the walls. The granular soil should contain no more than 10 percent material passing the#200 sieve, and preferably no more than 40 percent material passing the #40 sieve. The clean on-site sands should meet this gradation specification. The backfill soil .riie0 Engineering Consultants Inc