Abstract: A prefabricated structural element and a method of bonding wallboard to structural elements such as trusses for use in construction or prefabrication of ceilings or walls. The method involves applying a resilient polyurethane foamable liquid by a high pressure impingement mixing spray gun onto areas of a clean, dry wallboard substrate which have wood trusses or studs placed upon them. The foam is sprayed on the drywall at the juncture with the wood members on both sides of the wooden members. The resulting bonded structure permits the unit to be used without further nailing or other attachment means. The foam also permits the combined product to present a flat surface regardless of irregularities in the wood trusses.