Similar to tar and gravel roofing, the modified bitumen (torch down) roof consists of layers of fiberglass and polyester with bitument that are added to the regular tar and gravel layering system. These extra sheets are torched down in the overlap areas during the installation process, using large flame throwing torches that melt the asphalt at the seams to join them together, which is the origin of the name torch down roofing. The final result is the vulcanization of a large rubber sheet onto a fiberglass base.
Also called torch down, due to the mixing of asphalt with rubber compounds, torch down roofing provides additional strength and resistance to a flat or low sloped roof. It is not, however, suited to areas prone to high rainfall or snowfall, and has an average life expectancy of about 15 years. A torch down roof is also significantly more attractive than a standard tar and gravel roof.