Originally Posted by jlhaslip
Plastic is required under slabs of occupied spaces by code here.
It stops the ground from removing water from the mix so the slab hydrates properly.
crawlspace is not considered habitable space, so a rat slab would not require plastic beneath it.
the problem isn't "the ground removing water from the slab" but the ground introducing water to the slab. while it's true that heat and sunshine can prematurely dry a pour, causing surface cracks, once the chemical curing process is finshed, there is nothing "proper" about hydrating a slab.
plastic is layed down to prevent moisture in the soil from seeping into the slab, not the other way around.