Pipes and other roof penetrations can compromise the integrity and weather-resistance of an entire roof structure. These penetrations allow moisture to seep into roof insulation and framing below the roof tiles, which may lead to rot, mold, or other issues. To prevent water from infiltrating the roof structure, builders install metal flashings and counterflashings along roof penetrations and transition areas. While traditional metal boots or pipe sleeves can be used to protect standard-sized objects, irregular objects may require a specialty flashing known as a pitch pocket. Made from sheet metal such as aluminum or steel, pitch pockets fit around many different types of roof penetrations to keep water out and help protect the roof structure.
A standard pitch pocket resembles a top hat, with an open top and bottom. The flanges at the base of the device fasten to the top of the roof structure, while the vertical sections fit around the pipes or other objects in the roof. Typically, these devices hinge or open up along one corner for quick and easy installation. Installers then align the open seam using built-in connectors or grooves. Some models may require welding or specialty adhesive, while others can be hammered together using an interlocking seam.
Originally, coal or tar pitch was used to seal these fixtures to the roof deck, which is where the pitch pocket gets its name. Today, installers may pour hot asphalt or grout into the top of the pocket to form a tight seal. By filling all the gaps between the base of the pocket and the roof, the asphalt prevents water from leaking into the roof. Some pockets come with special sealers rather than grout or asphalt for easy installation. Builders should be cautious to find a compatible material that won't damage the existing roof when looking for ways to seal the pitch pocket.
Pitch pockets should not be used to support or fasten pipes or other objects to the roof. They are also not designed to prevent shifting or movement of these objects. All pipes and other objects should be properly secured before the pocket is installed to reduce the risk of roof damage.
Pitch pockets are often paired with a storm collar or other form of counterflashing to further reduce the risk of leaks. The storm collar fits tightly around the diameter of the pipe, then extends out at the base to cover the top of the device. The storm collar should be long enough to completely cover the rim of the pitch pocket, and wide enough so that all rain or moisture falls to the roof well outside of the flashing.