Poly under slab on grade…
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I’ve understood that poly sheet plastic of at least 6 mil should go directly under a cement slab on grade. At times I have read that the poly sheet can/should go below the rigid foam. I will be having pex imbedded in the cement slab, for radiant heating, if this makes a difference. Is there a preference on where the poly sheet goes?
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Link:
"Polyethylene Under Concrete Slabs"