Sheet metal is used to make a pocket.
Pipes and other roof penetrations can compromise the integrity and weatherability of an entire roof structure. These penetrations allow moisture to penetrate the roof insulation and the structure beneath the shingles, which can cause rot, mildew or other problems. To prevent water from seeping into the roof structure, builders install metal flashing and counterflashing along roof penetrations and transition areas. While traditional metal boots or tube sleeves can be used to secure standard-sized objects, irregular objects may require special flashing known as a pitch pocket. Made from sheet metal such as aluminum or steel, the slope pockets fit many different types of roof penetrations to keep out water and help protect the roof structure.
To prevent water from seeping into the roof structure, builders install metal flashing and counterflashing along roof penetrations and transition areas.
A standard pitch pocket resembles a top hat, with the top and bottom open. Flanges at the base of the device attach to the top of the roof structure, while the vertical sections fit around pipes or other objects on the roof. These devices typically fold or open along a corner for quick and easy installation. Installers then align the open seam using recessed connectors or grooves. Some models may require special soldering or adhesive, while others can be hammered together using an interlock seam.
Originally, coal or tar pitch was used to seal these light fixtures to the roof deck, which is where the pitch cavity gets its name. Today, installers can pour hot asphalt or mortar on top of the pocket to form a watertight seal. By filling in all the gaps between the base of the bag and the roof, the asphalt prevents water from leaking onto the roof. Some pockets come with special sealants instead of mortar or asphalt for easier installation. Builders should be cautious to find a compatible material that will not damage the existing roof when looking for ways to seal the pitch pocket.
Tilt pockets should not be used to support or secure pipes or other objects on the roof. They are also not designed to prevent displacement or movement of these objects. All pipes and other objects must be properly secured before installing the pocket to reduce the risk of roof damage.
Field pockets are often combined with a storm collar or other form of counterflash to further reduce the risk of leaks. The protective collar fits tightly around the diameter of the tube and extends from the base to cover the top of the device. The storm collar should be long enough to completely cover the edge of the field cavity, and wide enough for any rain or moisture to fall onto the roof well out of the flash.