There are some roofing details that do not work, have never worked and will never work.
As roof consultants, we inspect millions of square feet of roofing each year. This includes analysis of existing systems and inspection of roof construction. Over the years, we have observed workmanship defects in the field and have identified material concerns in our laboratory. Most of these types of problems are concentrated in the membrane application process. We have also witnessed problems that were attributed not to poor workmanship or inadequate material, but rather to improper design. These types of problems are directly related to flashings, penetrations and accessories. We can conclude that there are some roofing details that do not work, have never worked and will never work. Following are some of these details along with design recommendations to avert these problems in the future.
In a majority of the flashing problems that we have encountered, moisture ingress occurred at splits in the flashing material. These splits occur at points where metal was applied directly over the membrane, such as at perimeter gravel stops.