Build up roofing systems or BUR roofs have been around for a long time.
This type of roof uses three or more layers of materials, one being hot tar, to create a watertight barrier. This was and still is, in some areas of the country a very labor intensive and dangerous way to roof commercial buildings. Since the advent of the modified bitumen roofing system, or what is known “torch down” roofing. Some of my counterparts have adopted this more cost effective and much less dangerous way to get the same results.
This first type, two-step process that involves rolling out a base sheet of material over the substrate and then following that step with a roll of cap sheet on top of the base sheet. Unfortunately, this process isn’t without its degree of dangers either. A torch connected to a propane tank is used to heat the material up while installing each layer. This asphalt melting technique is used to promote the watertight bond with this type of roofing.