An aquaintance of mine indicated his 4 year old home was starting to have some of the ceramic floor tiles loosen up. The house has a post tensioned concrete slab. He indicated that there was some "black stuff" between the ceramic tile, thinset and slab. The way he described it, it sounded like tar paper.

I haven't personally seen it yet, but I haven't seen anything go between the slab and tile (other than thinset) on any houses I have looked at during new construction.

For what its worth, he indicated the house was built by Village Builders.

Is this something used as a vapor barrier?

I will try to get some photos of it.