A polyvinyl floor or decking system for use on indoor and/or outdoor applications, including porches, decks, patios and marine docks. The system comprises a plurality of extruded, generally hollow elongated polyvinyl or plastic tubular members which are placed on a supporting frame or structure in a conventional manner. Each of the members includes a plurality of grooves on the top surface in order to maximize surface friction and provide a better walking surface in all conditions, and further includes a bottom surface, and a pair of side surfaces. Each of the side surfaces includes a plurality of slots that are spaced so as to generally overlie the supporting joists. A plurality of mounting cleats engage the slots on adjacent members, and secures the members to the deck and to each other. The cleat in slot arrangement allows for the different rates of thermal expansion and retraction of the polyvinyl deck members compared to the supporting wood frame.