Single-ply roof systems, especially of the modified bitumen and TPO varieties, are known for their super tough durabilities. However, in modified bitumen systems, ESPECIALLY here in Capitol Hill, DC, it is all too common that the installers of modified bitumen roofs are not well experienced using a propane roofing torch. In cases like this, its better for them to under-do the job than over-do the job. Over-torching a roof system can have devastating consequences.
When lap joints are not fully adhered, after the first several years of exposure to the elements and ultraviolet rays, the seams will start to delaminate. Delamination is the process of materials installed, lapped on top of one another, separating. When delamination happens, heavy rain, coincident with temperatures around freezing, will actually build up and put a lot of pressure on these old bad joints.