When installing our Stone Flex Tiles in a basement, a vapor barrier is not necessary. If you do have moisture issues, we would recommend sealing your concrete floor; This will keep salts, minerals, and moisture from collecting on the tiles. We do recommend that the concrete is somewhat level. If there is some minor imperfection in the concrete, in most instances the tiles will lay perfectly fine. But if there are major imperfections, they will need to be addressed before installing the flooring.