Torchdown roofing is one of the most popular types of roofing materials in all parts of the world for buildings with flat roofs or 1-degree sloped roofs. Torchdown roofing, also called modified bitumen roofing, involves laying down fiberglass base sheets on the flat sub-roof, and then applying sheets of flame-activated rubberized asphalt membranes which are vulcanized onto the fiberglass base sheet by means of hand-held torches. This type of roof has largely replaced hot-tar and gravel roofing due to its clean look, ease of installation and durability; however, it is not recommended for areas that experience heavy rain or snowfall, because pooling water has been known to penetrate the overlapping roof membranes or cause leakage problems at penetration points.
Torchdown roofing has gained a following with building owners and contractors because it is moderately inexpensive, easy to install, and it combines excellent weather resistance with long-term strength and flexibility. In addition to being highly flexible and able to withstand extreme temperature changes, the material is resistant to punctures or tears, as well as to chemicals, grease, and ultra-violet radiation from the sun. Multi-ply torchdown roofing has a life expectancy of up to 20 years with no leaks if properly installed and maintained. Repairs are simple as well, since most modified bitumen manufacturers also make a self-adhesive product that can be applied over seams and other troublesome areas of the roof.