A floor panel having a structural core and a finished surface layer disposed on a top side of the structural core. A substantially water-impervious sheet having a plurality of projections for providing an air gap between the core and a concrete foundation is affixed to a bottom side of the structural...http://www.google.es/patents/US20030154676?utm_source=gb-gplus-sharePatente US20030154676 - Floor panel for finished floors
