Modified Bitumen (Two Ply) systems have been well established over the past forty years. They have proven to be hearty having elastomeric qualities that permit thermal expansion and contraction of the membrane during extreme temperature changes such as we experience here in Southern Ontario.
The first ply consists of a smooth surfaced base ply and the top ply is referred to as a granulated cap sheet. The embedded ceramic granules of the cap sheet serve to reflect the sun’s ultraviolet rays which are the common degrading enemy of all asphalt based roofing products. The application of the base and cap sheets in the assembly requires that the finish ply is offset by fifty percent from the proceeding layer.
Application of modified bitumen assemblies can be adhered using hot asphalt, cold process adhesives and open flame torch welding.
For roofs that have wooden substrates, ARR® prefers the cold applied methods as they reduce fire risk and provide uniform adhesion and bonding of the two membrane plies. The trend moving forward will increasingly embrace this installation method as a safer, low odour solution, and preferred by many insurers.
Torch-applied methods involving open flame are still the most common among many roofers, but fire risk is obviously increased, and bonding of the membranes is reliant on even temperature application in the field of the membrane and strict attention to bleed-out consistency on all overlapping seams.
Hot asphalt application of modified bitumen provides for speed of field installation but can be slower on commercial roofs that have lots of appliances such as HVAC equipment and various roof appliances.
Maintaining the correct asphalt temperature level is key when applying, so it tends to be less popular in colder climates where high production of roofing application must be accomplished.
