Residential metal roofing is primarily made of steel or aluminum. Copper, zinc and titanium are also used in specialized architectural applications for homes.
Steel roofing for residential applications is very lightweight with the heaviest product weighing about 1.5 pounds per square foot when installed. The products are initially produced in giant rolls at the steel mills. They are then coated with a metallic coating to prevent rust at the steel plant.
The rolls are then painted at a coil coating plant using high-speed paint lines that bake on the coating. The painted coil is then shipped to a roofing manufacturer where it is formed into long panels by a process called roll-forming or they are stamped into individual shingles using large presses.
Aluminum roofing follows the same process except that it does not require the metallic coating step. Steel residential roofing is made in thicknesses designated by gauge and is generally 24 to 26 gauge, with the higher gauge being thinner than the lower. These gauges are appropriate since most residential metal roofing applications are over a solid substrate.
Aluminum residential metal roofing is designated by decimal thickness and ranges from .023 to .040 thickness.
Granular coated steel shingles, shakes, tile are a special category and are produced by stamping galvanized steel (26 gauge) then sprayed with an acrylic coating embedding granular stone then baked in an oven at the factory.