Precon is a composite sheet membrane comprised of a non-woven fabric, elastomeric membrane, and W. R. Meadows' exclusive, patented plasmatic core. The plasmatic core is a seven-layer matrix designed for toughness and provides the lowest water vapor transmission (WVT) rating on the market. Once concrete is poured against Precon and the concrete cures, a mechanical bond forms that secures the concrete to the membrane.