Put Plastic Under Concrete Slab

The other contractor says no way no plastic holds the water in the concrete during the drying process and can leave webbing like visual affect in finish of concrete.

Put plastic under concrete slab.

This was verfied by some field studies conducted by concrete construction magazine. Thanks for the question. It doesn t really matter very much whether the pex is near the bottom of the slab in the middle of the slab or at the top of the slab as long as there is plenty of insulation under the slab. Don t worry if the concrete contractors put a few holes in the poly.

Vapour barriers are the black plastic that builders put under residential house slabs. One laboratory drying study indicated that 4 in. Thinner plastic can t stand up to the abuse of construction. Why a plastic vapor barrier under concrete slab mondays withinstall the proper type of vapor barrier siouxland homesare vapor ers necessary for bats and garagesvapour barrier under concrete.

There are debates about this with varying national regional state and local regulations. Aci 302 1 guide for concrete floor and slab construction states that the minimum thickness of an effective vapor barrier is 10 mils. Thick concrete samples having a w c 0 50 and sealed from below required 82 days for the vapor emission rate to reach 3 0. Plastic under concrete floor or not.

A concrete vapor barrier is simply a sheet of polyethylene plastic visqueen placed directly on top of the sub grade before the concrete floor or slab is poured to help keep moisture from the soil from passing up through the concrete. The rate that moisture escapes from a slab depends on the concrete w c the density of the finish the ambient conditions above the slab and the moisture below the slab. They do this for two main reasons. One contractor says to put plastic under the concrete it prevents moisture from coming up into the concrete.