Metal roofing is a sheet metal roof material, structure and waterproof layers in one roof forms. Many types of sheet metal, Zinc plate, aluminum plate, aluminum plate, aluminum-magnesium alloys, titanium, copper, stainless steel, etc. General 0.4~1.5mm thick, the surface coating treatment. Due to the quality of materials and coatings, some life of 50 years or more. Making shapes are varied, some composite panels, insulation layer between two layers of sheet metal, as well as for veneer, construction, some processed in a factory assembled, according to project needs in the field of machining. Good heat-insulation layer in the factory compound, can be produced on site. Sheet metal roof in various forms, from large public buildings to plant, warehouse, residential and other uses. So that the scope of the specification sheet metal roofing was waterproof rating for I~III roof.