This day and age most factory roofs are weather proofed with metal roof sheets with an uPVC coating. These roofing sheets come in various sizes and profiles but all consist of the same material. The roofing sheets are cut to various sizes once they have been manufactured. When the sheets are cut they leave and exposed edge, allowing it exposed to the outdoor elements (rain, snow, frost). As these metal roofing sheets are generally used on low pitched roofs (15 ...