Torch-on roofing is named due to the use of an open flame torch for the application of the reinforced bitumen membrane. Torch-on reinforced bitumen membranes are used predominantly for low-slope and flat roofs.
What are the two types of modified bitumen used for torch-on applications?
The two main types of reinforced bitumen membranes that are used to modify torch-on bitumen felts are:
SBS – Styrene Butadiene Styrene is a rubber-modified bitumen.
APP – Atactic Polypropylene is a plastic-modified bitumen.
SBS modified bitumen membranes are the most used within the UK. Often referred to as elastomeric roofing membranes, SBS modified bitumen torching membranes offer high-performance flexibility even at low temperatures.
This flexibility means it has recovery properties, making it capable of withstanding stresses created by temperature fluctuations, expansion, and contraction. SBS modified bitumen membranes also take less heat to apply than APP membranes.
APP modified bitumen torching membranes are typically only used with torch-applied membranes. They are more plastomeric, making them stiffer than SBS modified membranes. They require great heat to apply due to their plastomeric characteristics; however, they are less prone to foot marking during the installation process.
Why is torch-on roofing used?
Torch-on roofing membranes have been around for many years, and are used because of their excellent waterproofing qualities, long life span and ease of installation.
Torch-on roofing membranes come in various forms; they can be glass fibre or polyester reinforced to provide extra durability, or they can be used as air and vapour control layers where the membrane has been reinforced with an aluminium foil, which can form part of a warm flat roof construction.
They are also available as a range of underlays used within a built-up roofing system and as a capsheet which has factory-applied minerals that provide UV stability and long-term performance.
Where is torch-on roofing used?
Torch-on roof membranes can be specified for non-combustible substrates such as metal and concrete roof decks. However, they should not be used on timber structures due to the potential fire risk.
The cost efficiency and relatively easy installation in all weathers make torch-on popular for a wide array of new applications and roof refurbishments. It can be used almost anywhere, from small domestic projects to large commercial applications.
It is, however, crucial to follow the Safe2Torch guidance from the National Federation of Roofing Contractors (NFRC) to ensure safe installation.
