While Modin Rigid Vinyl Plank is waterproof, it is not a moisture barrier. It's a good idea to install a moisture barrier in the crawl space and between Modin Rigid Vinyl Plank and your concrete subfloor.
A moisture barrier is not necessary for the sake of the flooring itself, as the Modin Collection is 100% waterproof. If you are installing over a concrete slab with a lot of moisture rising from it, we recommend installing a moisture barrier to help control the humidity of your room, though.
Moisture won’t damage Modin Rigid Vinyl Plank, but it can get in the walls and structure of the home. Mold could develop, and that can cause certain medical reactions in pets and people. As such installing a moisture barrier is a smart idea, even if the Modin Rigid won't damage.