The most common source of roof leaks is at vertical transitions and penetrations. Most designers provide adequate details to wall and curb flashings and common penetrations such as vents. Problems occur at mechanical support penetrations, multiple pipe penetrations or electrical conduit from mechanical equipment. It is not uncommon to see variations of waterproofing techniques at these types of penetrations. Problems can range from no waterproofing at all to misguided attempts to use wrapped membranes.

Multiple pipe penetrations and conduits are ideal candidates for pitch pan applications. Pitch pans are fabricated from metal (or copper) that is set in two pieces and soldered to form a box around the penetration. Pitch pan boxes are applied over the completed membrane surface on BUR and single-ply roof systems and over the base ply on modified bitumen systems. The pitch pan flanges are covered over with a strip-in material or modified bitumen cap sheet. The metal flanges typically extend onto the membrane surface a minimum of 6 inches and the strip-in material should be applied a minimum of 6 inches beyond the flange.