Do you need any plastic or underlayment when installing over basement concrete to prevent mold? Floor not normally damp, just trace amount of moisture evaporation through the concrete.

You do not need to place a plastic sheet under our 3/8" Tight-Lock Tiles to prevent mold. Our rubber flooring is naturally mold and mildew resistant. If you do have moisture issues, there are a few things you may notice. One is 'sweating.' This is when moisture collects on the surface of your flooring. They occur because the moisture is condensing on the flooring surface. The second is that when the water evaporates under your tiles, you will see this white material under the tiles. This is not mold, but actually, salt from your concrete. It is not harmful at all and can be cleaned easily with a mild soap and water solution.