# Plastic under concrete



## Marshall_NB (Sep 12, 2008)

When pouring concrete flooring, what does plastic do underneath rather than insulation?


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## Animal (Sep 14, 2008)

Vapor barrier. It keeps the water from migrating in in a vapor form through the concrete.
Also helps to keep radon gas out if it is installed correctly with ventilation.


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## tectonicfloors (Nov 22, 2011)

Concrete does not cure by drying out but through a process call hydration. Installing a barrier such as polyethylene below the slab retards the transfer of moisture from the ground to the concrete.


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