Underlay including a moisture barrier for floating floors installed in commercial and residential areas. PolyFoam is recommended for use with all Junckers solid hardwood floors, where a moisture barrier membrane is required. PolyFoam is a resilient, step sound-absorbing 2 in 1 underlay mat for floating floors. It consists of a polythene membrane laminated to an extruded foam mat in such a way as to allow a 100 mm overlap of polythene on one side with built-in tape. PolyFoam is non-absorbent and must be laid foam-side down to prevent perforation of the membrane by sand or gravel particles.