Moisture is something to be managed. A vapor barrier can cut down on earthy smells, mildew, and general humidity.

2 (2) If figure 2 is used, a reduced joint spacing, a low shrinkage mix design, or other measures to minimized slab curl will likely be required. Vapor retarders are often called vapor barriers.

If you're installing concrete slabs in a basement or another area of your home, you'll also need to install a vapor barrier to add protection. While not strictly required, you also need to add a ...

“The terms vapor barrier or vapor retarder have a tendency ... Used in Contact with Soil or Granular Fill under Concrete Slabs) defines three classes of membranes: A, B and C.