Subfloors & Underlayments

New and existing concrete subfloors must meet the requirements of the latest edition of ASTM F 710, “Standard Practice for Preparing Concrete Floors to Receive Resilient Flooring,” available from the American Society for Testing and Materials, 100 Barr Harbor Drive, West Conshohocken, PA 19428; 610/832-9500; http://www.astm.org

Note: Regardless of the type of concrete or other cement-like material used as a base for resilient flooring, in the event of underlayment failure, the responsibility for warranties and/or performance guarantees rests with the concrete or cement-like material manufacturer and not with the manufacturer of resilient flooring.

Above-Grade Concrete Floors

1. Above-grade concrete is usually protected from most sources of moisture except the moisture initially in the mix and water vapor in the atmosphere. However, as with concrete placed on and below grade, it must be kept damp during the curing process to permit hydration to occur. Concrete poured on a metal deck is often produced with lightweight aggregate, which can retain excess water longer than normal-weight aggregate. Because drying is only possible from the top surface, such construction usually takes additional drying time.
2. Floors in metal deck or structural concrete floors above grade must be dried and must meet the same requirements as described above for slabs on- and below- grade.
3. Before installation of the finished flooring, moisture, alkali, and bond testing must be conducted.
   1. Moisture testing must be done according to ASTM F 2170, “Standard Test Method for Determining Relative Humidity in Concrete Floor Slabs Using in situ Probes” (preferred method) or in accordance with ASTM F 1869, “Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride.” See section on Moisture Testing for more details.
   2. The surface of the concrete must have a pH of 9 or less.
   3. Bond testing must be run to determine compatibility of the adhesives to the concrete slab.