Stagestep Plastic Vapor Barrier is an 8 mil thick tri-layer plastic sheet comprised of a reinforcement scrim laminated in between 2 polyethylene layers. The use of Stagestep Vapor Barrier or better, or Bone Dry liquid application, is mandatory when installing our products over, above (with less than 18" of well ventillated space), on or below grade concrete. Failure to do so will void all warranties. Vapor Barrier should run up the wall at the perimeter and each roll overlap using moisture proof tape such as duck tape. Stagestep Cloth and Gaffers tapes cannot be used for this purpose.