Torch-on roofing, or torch-down roofing as it is also known, is a flat roof covering solution that involves three layers of modified bitumen (felt) melt-welded onto the roof surface and each other with the use of a blowtorch to create an impenetrable, waterproof seal.
Traditionally, the three layers used in this process are a vapour control sheet, reinforced felt and a cap sheet with mineral finish. Using three layers of felt is required by building regulations for habitable areas of a home. For sheds and garages, only two layers may be needed.