Action-Bac carpet backing is a stretchable carpet backing made of a web or weave of plastic. Carpeting with Action-Bac backing, when wet, often stretches to the point where, even after drying, it appears loose or baggy. Use Action-Bac carpet backing in a room that is not prone to high humidity.
Moisture barrier carpet backing is commonly composed of solid vinyl or urethane with the main purpose of keeping water-based spills from seeping through the carpet. While this is a positive aspect to this carpet backing, there is one downside; moisture sometimes become trapped, preventing proper evaporation and causing damage to the concrete and the glue.
Polyurethane carpet backing is actually a polymeric resin applied during the finishing process. During curing, it reacts and creates a foam-like texture. This type of carpet backing encases the yarn, giving it extra tuft bind as well as a cushion. In addition, it also acts as a water repellent to create a moisture barrier.