a method of manufacturing an exterior facing layer for vinyl siding , including molding a pattern of depressions and protuberances into a sheet of a thermoplastic polymer simulating cedar shake shingles , and concurrently molding an extension to the molded plank incorporating an integrally molded hinge connection . thereafter , the extension is folded over the plank edge in a mechanical bending sequence and bonded thereto . in another embodiment of the invention , a foam filler material may be poured into the molded facing layer cavities and a metallic foil backing bonded thereto so as to form a laminar siding construction .