Abstract: A panel for use as a substrate for a torch-down modified bitumen roof membrane is disclosed. The panel comprises a board of combustible material with a pre-applied noncombustible facer sheet. The facer sheet protects the board from burning during installation of the membrane. In a preferred embodiment, the boards comprise cellulosic fibers and the facer sheet comprises a fabric of bituminous coated glass fibers. The panels are provided with a facer sheet overhang along two adjacent edges for overlapping the facer sheets of abutting panels. The panels are disclosed having an asphalt coating on the top of the board and with a rubber-asphalt emulsion adhesive adhering the facer sheets to the board. Also disclosed is a roofing construction and a method of applying the roofing construction incorporating the substrate panels.