Pitch Pan Flashing

It is very common to install pipes or other penetrations for supports through the roof surface. Typically, these supports are flashed in with a rectangular box that is referred to as a pitch pan. This type of detail is common with all membrane systems and installation is similar with all of them.

The pitch pan can be fabricated from metal or plastic. Most single-ply (thermoplastic) manufacturers have pre-molded pitch pans. The diameter of the pitch pan is based on the size of the pipe that it is applied around; there should be a minimum of 2 inches of clearance between the pan and the pipe. The pitch pan corners should have a 2-inch radius and are lapped a minimum of ½ inch. There should be a minimum 4-inch flange at the perimeter of the pan that serves as a base over the membrane surface.

The membrane should be set to the opening with manufactured-approved flashing applied at the perimeter of the pitch pan covering the flange. A bead of caulking at the flashing/pitch pan top intersection is recommended. The detail provided illustrates modified bitumen applications, but details are similar with all membranes.

 Pitch pans are filled with grout materials to hold pipe in place and limit movement. Best practice recommendation is to cover pitch pan with a metal fabricated cover; this eliminates the need for constant maintenance of refilling the grout material.