Vapor Barrier is a superior quality waterproof plastic used beneath foundation applications. Vapor Barriers restrain harmful pollutants, such as radon, methane and petroleum hydrocarbons. Many sources of toxic vapor are underground soil, ground water, storage tanks and septic systems. Vapor Barriers are also placed in walls, floors, ceilings and crawl spaces which control absorption and condensation of moisture, preventing mold. Vapor Barrier plastic is offered in 10mil and 15mil.