Provided are encapsulated belts and encapsulated pads for use in a variety of polishing application, including the chemical-mechanical polishing and planarization of semiconductor wafers and other workpieces. The encapsulated belts and pads are characterized by a robust seal between a polishing layer of the pad or belt and the edges of the subpad layer of the pad or belt. The robust seal is accomplished by casting a polymer directly over the subpad layer. The edges of the subpad layer may include one or more functional features that promote the formation of a watertight and slurry-resistant seal when the subpad layer is covered with a cast polymer. Also provided is a method of producing a robust seal between the polishing layer and the edge region of the subpad by encapsulating a subpad layer with a polymeric material.