The primary difference between residential and commercial or industrial roofing is the scale. Commercial and industrial buildings are most often much larger than their residential counterparts. This means more and heavier duty materials and more complicated ventilation and drainage systems. The majority of commercial and industrial buildings in Southern Ontario are flat roofing surfaces. However, especially on commercial buildings, there are also many pitched roofs. Popular roofing systems for large scale flat roofing include EPDM rubber, modified bitumen, tar and gravel and tile. For pitched roofing applications in the commercial and industrial sectors, use the same covering materials (shingles, metal tiles, sheet metal) with commercial grade underlays.