Torch down installation

With the base sheet installed, we moved right on to the torch down membrane, while the dry weather lasted.

This process resembled the installation of the base sheet. The torch down membrane came in 36 inch wide rolls and also were rolled out across the roof, starting from the low end. The difference was that the torch down membrane needed to be heated with a torch (thus the name). The heat was applied to the bottom side of the membrane to soften the asphalt, which acted like a glue, and immediately rolled across the roof. Once rolled out, the melted membrane bottom cooled down, firmly adhering it to the base sheet.

Let me state that I appreciated the skills and confidence of our seasoned roofer, Pablo. My mind was racing with thoughts such as, “how do we properly line up each layer?”, “how far up the parapet do you go?”, ”how do you manage the joints at the end of one and beginning of another role?”, “how do you know when the roll is heated enough?”,etc.

While my mind was racing, Pablo had already installed the first couple of rolls. It was time for me to stop thinking and start watching, and eventually grab a tool and give him a hand. And the answers all arrived automatically:

How do we properly line up each layer?

The overlap between the torch down rows should not be on top of the overlaps of the base sheet rows. Pablo started with half a sheet so that the overlaps were perfectly staggered. Like with the base sheet, we started at the bottom of the roof working our way to the top. This way the overlap was in the direction of the slope and waterflow. Like with the base sheet, the torch down membrane has markings that tell you how much overlap is needed, and allows you to overlap perfectly straight.

How far up the parapet do you go?

Pablo went up the same distance as he did with the base sheet, basically over the cant strip and another four inches up. He stopped with the torch down just a notch below the end of the base sheet.

How do you manage the joints at the end of one and beginning of another roll?

When one roll ended, we slipped the new roll under it to get the same overlap as between each layer, which was four inches. It is basically the same overlap, just perpendicular to the layers.

How do you know when the roll is heated enough?

I still have no idea, and I am still not interested in finding out. Pablo pointed out that you need to be “very careful.” And knowing that Pablo is a master of understatements, I had no intention to ever use that torch and heat up the roll.

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About Marcus de la fleur

Marcus is a Registered Landscape Architect with a horticultural degree from the School of Horticulture at the Royal Botanic Gardens, Kew, and a Masters in Landscape Architecture from the University of Sheffield, UK. He developed a landscape based sustainable pilot project at 168 Elm Ave. in 2002, and has expanded his skill set to building science. Starting in 2009, Marcus applied the newly acquired expertise to the deep energy retrofit of his 100+ year old home in Chicago.

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