Metal roofing refers to a roofing system that uses metal sheets as the roofing material, integrating the structural layer and waterproofing layer into one. There are many types of metal sheets, including galvanized sheets, aluminized zinc sheets, aluminum alloy sheets, aluminum-magnesium alloy sheets, titanium alloy sheets, copper sheets, and stainless steel sheets. The surface of the sheets can be painted, primarily with PE/PE, SMP/PE, HDP/PE, and PVDF/PE coatings. Painting can extend the lifespan of the sheets to 5-8 years, 10-15 years, 15-20 years, and 20-25 years or more, respectively.
The thickness is generally 0.4–1.5 mm, and the surface of the sheets is usually coated. Due to differences in material and coating quality, some sheets can have a lifespan of over 50 years. The sheets come in various shapes and sizes; some are composite sheets, where an insulation layer is laminated between two layers of metal sheets, while others are single-layer sheets. During construction, some sheets are prefabricated in the factory and then assembled on-site, while others are fabricated on-site according to the needs of the roofing project. The insulation layer can be pre-laminated in the factory or fabricated on-site. Therefore, metal sheet roofing comes in various forms and is used in everything from large public buildings to factories, warehouses, and residences. Consequently, the regulations stipulate that metal sheet roofing is suitable for roofs with waterproofing grades I to III.
