series of perforations 68 passing through it these perforations may serve two functions they allow for water vapors that occur upon the dehydration curing of the latex modified asphalt in the core layer 56 to move upwards also upon laying the concrete structural slab on the bond layer the perforations 68 allow water penetration and vaporization to aid in the curing of the concrete slab fig4 shows a flow chart of a method of preventing contaminant vapors from entering a building in step 72 a sheet of the base layer is applied to the soil this may comprise for example base layers 22 36 or 54 this step may also include adding openings for penetrations such as opening 30 the core layer is then applied on the base layer in step 74 this may comprise core layer such as core layers 24 38 or 56 in step 76 the base layer is also applied to the penetrations and edge regions of the base layer this may include penetrations such as pipe 28 and opening 30 as well as the perimeter edges of the base layer in step 78 the bond layer such as bond layers 26 40 or 58 is applied to the core layer in step 80 an additional core layer may be applied to the top of the bond layer where it will overlap with an adjacent vapor barrier for.