A process of pre-applying a vapor, water and ice layer to a sheathing panel before the sheathing panel is assembled onto rafters of a roof is disclosed, comprising the steps of positioning a face of the sheathing panel for accessibility, removing a plastic film from the vapor, water and ice layer, thereby exposing an adhesive surface of the vapor, water and ice layer, joining the adhesive surface of the vapor, and water and ice layer to the face of the sheathing panel to form an assembly, thereafter, transporting the assembly to the roof, and securing the assembly to the rafters of the roof.An article of manufacture for reducing water and ice damage caused by an ice dam on a roof is disclosed, wherein the article of manufacture is pre-assembled prior to assembly to rafters of the roof, comprising a sheathing panel for assembling on the rafters of the roof having a first face and a second face, a vapor, water and ice layer having a first side and a second side, the second side having a plastic film covering an adhesive backing, means for removing the plastic film to expose the adhesive backing and means for assembling the vapor, water and ice layer to the sheathing panel, wherein the second side of the vapor, water and ice layer having the adhesive backing is placed onto the first face of sheathing panel before assembly of the sheathing panel to the rafters of the roof.