Under slab vapor barrier at two levels
I am retro fitting a existing slab on grade barn into a home , in order to accommodate plumbing, the run of the stairs and other , I am raising the floor. 2 to 4 inches of sand will be added followed by 3 inches of reclaimed XPS , then a 4 inch stained concrete finished floor. Typically I would top the foam with a vapor barrier, however there is a vapor barrier under the slab now. So I wonder if having 2 vapor barriers separated by the original concrete , sand , and foam creates a problem. Basically the sand and any moisture in lower concrete never dries out.. So being that I will have no flooring on the top of the finished layer of concrete would it make the most sense to skip the top vapor barrier?
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