For crew-friendly modified bitumen installations, self-adhering and torch-applied cap sheets are the clear choices. Like all mod bit membranes, they are tough, durable, incredibly weather-resistant, easy to maintain and budget-friendly … without the need for messy, stinky cold-process adhesives or kettles of smelly hot asphalt.
As highlighted in Part 2 of this series, crews appreciate self-adhering systems for their quick, clean, torch-free installation. But torch-applied membranes are the classic choice for outstanding, long-term performance and durability, and are the ideal solution in many circumstances.
As the name implies, they are installed using propane-fueled torches – generally a hand-held roofing torch for flashing and a rolling torch wagon for the field sheet. The welder melts the asphalt surfacing compound, turning it into a liquid that, as it cools, forms a bond with the substrate.
Torch-applied membranes often cost less than self-adhering systems, and because the membranes are adhered using traditional torch roofing techniques, seams can be completed in conjunction with the field sheet, speeding up installation. The technique does require knowledge and finesse that only come with training and experience, however, so it should be left to professional crews.
Any torch-applied roofing installation comes with an inherent risk of fire, and appropriate precautions must always be taken to protect people and property. But there are many jobs on which the risk of fire is small and a torch-applied system is an extremely safe option. For example, a new building under construction with a metal or concrete roof deck; the building is unoccupied and the lack of combustible materials makes the chance of a fire starting minimal.
Torch-applied systems also are far more forgiving of lower temperatures during installation than their self-adhering cousins are, making them the more appropriate solution when working in cooler weather. To ensure strong membrane adhesion and quality seam welds when installing torch-applied systems, extra care should be taken at ambient temperatures of 40 F to 45 F and below, and when ambient temperatures are affected by wind or humidity. And membrane rolls must be at least 60 F at the time of application, so having a heated storage area on-site is recommended during cold-weather work.
With more than 40 years of proven performance in the field, mod bit systems are low-slope roofing workhorses. And by mixing and matching cap sheet formulation and attachment method based on weather, crew experience, local regulations and other project-specific conditions, a system can be created to suit virtually any commercial building.