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CORNERSTONE C. EARTH GROUP These guidelines are based on information obtained from a variety of sources, including the American Concrete Institute (ACI) and are intended to reduce the potential for moisture-related problems causing floor covering failures, and may be supplemented as necessary based on project-specific requirements. The application of these guidelines or not will not affect the geotechnical aspects of the mat foundation performance. Place a minimum 10-mil thick vapor retarder conforming to ASTM E 1745, Class C requirements or better directly below the concrete mat; the vapor retarder should extend to within 12 to 18 inches from the mat edges and be sealed at all seams and penetrations in accordance with manufacturer's recommendations and ASTM E 1643 requirements. A 4-inch-thick capillary break, consisting of Yz- to 3/<-inch crushed rock with less than 5 percent passing the No. 200 sieve, should be placed below the vapor retarder and consolidated in place with vibratory equipment. At your option, the section of crushed rock could be reduced to no less than 2 inches, but would not be as beneficial as the 4 inches suggested above. • The concrete water:cement ratio should be 0.45 or less. Mid-range plasticizers may be used to increase concrete workability and facilitate pumping and placement. • Water should not be added after initial batching unless the slump is less than specified and/or the resulting water:cement ratio will not exceed 0.45. j Polishing the concrete surface with metal trowels should not be allowed versus light `_ broom or limited trowel finishing. ^ Where floor coverings are planned, all concrete surfaces should be moist cured (kept continuously wet) for at least 7 days by soaking burlap, cotton mats, or carpet, or frequent sprinkling. The moist cure method should be placed as soon after concrete finishing as possible, while resisting surface damage. Chemical curing may bean option depending on the floor covering type. ^ Water vapor emission levels and concrete pH should be determined in accordance with ASTM F1869-98 and F710-98 requirements and evaluated against the floor covering manufacturer's requirements prior to installation. 7.3 DRILLED PIERS 7.3.1 Vertical Capacity and Settlement Any proposed sound walls may be supported on drilled, cast-in-place, straight-shaft friction piers. The piers should have a minimum diameter of 12 inches and extend to a depth of at least 5 feet below the bottom of the grade beams or lowest adjacent finished grade, whichever is greater. Adjacent piers centers should be spaced at least three diameters apart, otherwise, a reduction for group effects may be required. Grade beams should span between piers and/or pier caps in accordance with structural requirements. Ponderosa Active Adult Community Page 19 132-2-1