The alternative to the hot tar built-up roofing system, this type of roof is installed with an open flame from a propane torch. One roll will cover 100 square feet and weighs between 90 to 105 pounds per roll. The material is made with an asphalt modifier and a polyester scrim which keeps the membrane flexible. The recommended installation of this material for optimum performance is a 3-ply system consisting of a mechanically fastened base sheet, a smooth mid-ply torch and a top-ply with ceramic granules. A 3-ply roof can last more than 20 years if properly maintained. The top ply comes in different colors to suit your needs. A 2-ply roof system is available in a smooth or ceramic granule finish. This is a good money saving option for anyone on a budget. The 2 ply smooth system will require periodic roof coatings to prolong the life of the roof. The average life expectancy of a 2-ply roof system should be 12 years if properly maintained.