Flashings and penetrations are particularly critical on low-slope standing-seam metal roof systems because the metal serves primarily as a watershed.
In all roofing systems, installation of flashings and penetrations are the most critical points of application. These areas typically account for nearly 80 percent of all reported roof leaks. Flashings and penetrations are particularly critical on low-slope standing-seam metal roof systems because the metal serves primarily as a watershed. The water shedding capacity is functionally similar to roof shingles, i.e., it relies on a steep slope to rapidly shed the water. In contrast to waterproof roofs, which are intended to function under occasional standing water, metal roofs are not designed to be completely leak-free under long-term water immersion. Therefore, waterproofing must be provided at critical junctures, such as flashings and penetrations.
A typical pipe penetration in the field of a metal panel is completed with a flexible bellow-type boot. The boot should be set over the penetration and installed onto the metal surface. Sealant is applied between the metal panel surface and the metal flange of the pipe boot before fastening the flange to the surface. This application detail is acceptable on all penetrations that are located within the flat part of the panel and can be completed on new and remedial roofing applications.