Two roofers are installing a small flat roof over a lanai while the homeowner is at work. The tear off goes well. Perhaps there’s a little rotted wood to fix but that, too, is no problem.
Then they start installing the new roof system. It is a type commonly referred to as “torch down roofing”. The official name is “modified bitumen” (pronounced buy-TOO-men). It is a rolled roofing product that consists of a tough membrane embedded in a thick layer of asphalt. Rubbery additives in the asphalt allow the roofing to expand and contract, where other roofing systems just crack. The roofing can bond tightly to metal flashings and move with them, while maintaining the bond. This flexibility is the main benefit of modified bitumen and is a big factor in its success.
Some types are applied with an adhesive, some types are self-adhering and some types are hot mopped as the cap sheet in built-up roofing systems. But it is the type applied with a propane torch that is referred to as “torch down roofing”. It is also one the most dangerous of all roofing products…
One of the roofers gets a little careless with the torch and starts something smoldering in the attic. And they don’t notice the small wisp of smoke coming out of the soffit vents. Just after the roofers go to lunch, the smoldering turns into a fire that spreads quickly in the dry, dusty attic.
With nobody home, the fire is going pretty good before the mailman notices the black smoke billowing up from the back of the house. He dials 911 and the fire trucks are there in a matter of minutes. But they have trouble putting the fire out because it is mostly contained within the attic. Finally they chop a big hole in the roof so they can put lots of water on the raging inferno. They get the fire out, but not before the home suffers extensive smoke and water damage, in addition to the actual fire damage.
One of the neighbors calls the homeowner, who rushes to the scene to find that the lovely home she had a few hours before, is now pretty much destroyed. About that time, the roofers come back from lunch… and wish they had taken up plumbing instead of roofing!