Missing poly under slab
I am finishing my basement and spent a lot of time here reading about how to insulate it.
Per all my reading, I am planning on putting down one inch of foam on the slab followed by two half-inch layers of plywood with no poly underneath. Based on what I’ve read here, since my house was built in 2008, it should already have poly underneath the slab. In fact, poly was specified to be under the slab on the building plans. My plan was to let the foam take care of stopping most water vapor from coming through and then the dehumidifier in the mini-split to take care of the rest.
However, they have just dug up my slab for the rough bathroom plumbing and… there was no poly! Am I correct in understanding it would be right underneath the slab? Under my slab was just gravel and sand and they have probably dug a foot beneath the bottom of the slab.
Assuming I’m not mistaken and it isn’t supposed to be deeper than that, what do you recommend I do? Stay with the plan even though it is missing? Or should I put down poly on top of the slab?
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