Abstract: A backerboard for use in conjunction with a siding panel of the type having longitudinally disposed walls connected by a longitudinal step and wherein the siding panel is normally fastened to the external wall sheathing of a building. The backerboard is adapted to be disposed between the inner surfaces of the siding panel walls and the exterior of the building sheathing. The backerboard is fabricated from two polystyrene foam plastic members that are disposed with respect to each other so as to have overlapping portions that are bonded to one another by a suitable adhesive such that the longitudinal side edge of one of the members adjacent the overlapping portions is contoured to snugly abut the step of the siding panel when the backerboard is positioned against the same. A method for manufacturing the backerboard is disclosed.

Abstract: A backerboard for use in conjunction with a siding panel of the type having longitudinally disposed walls connected by a longitudinal step and wherein the siding panel is normally fastened to the external wall sheathing of a building. The backerboard is adapted to be disposed between the inner surfaces of the siding panel walls and the exterior of the building sheathing. The backerboard is fabricated from two polystyrene foam plastic members that are disposed with respect to each other so as to have overlapping portions that are bonded to one another by a suitable adhesive such that the longitudinal side edge of one of the members adjacent the overlapping portions is contoured to snugly abut the step of the siding panel when the backerboard is positioned against the same. A method for manufacturing the backerboard is disclosed.