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• That a 4” thick slab can contain between 1,600-1,700 lbs. of non-chemically bound water in just a 1,000 sq. ft. area* • The moisture emission rate of concrete should not exceed 3-5 lbs. of water/1000 sq. ft/24 hours (as required by most floor covering manufacturers) • It would take the following drying time for a 4” slab to reach 3 lbs./1000 sq. ft./24 hours emission rate*
Bottom Sealed	Bottom Exposed (to vapor)	Bottom In Contact With Water
82 Days	144 Days	199 Days

• Relative humidity in the base and sub-grade material beneath covered slabs will generally test close to 100% (even when the moisture content is found to be low after drying) • 0.3 perm material allows the passage of approx. 18 gallons of water per week in a 50,000 sq. ft. area • Capillary action causes water (in liquid form) to rise above the water table and enter into slab • Diffusion is how water vapor (gas form) rises above the water table and enter into slab • The American Concrete Institute (ACI) Committee strongly recommends that the vapor retarder material be in compliance with ASTM E-1745 “Water Vapor Retarders Used in Contact with Soil or Granular Fill Under Concrete Slabs” and that the thickness be no less than 10 mils as stated in Section 3.2.3 of the Guide for Concrete Floor and Slab Construction (ACI 302.1 R-04). • Conventional polyethylene film (visqueen and/or C & A) with a thickness as little as 6 mils has been traditionally used but films such as these are generally made using a wide range of low grade resin which sacrifices physical strength, durability, longevity, resistance to decay and degradation, which then ultimately compromises the long term effectiveness of the permeability and moisture vapor protection because of its inconsistency. *When cement is mixed at 50% water/cement ratio [BACK TO MAIN PAGE]