Pitch Pockets
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Pitch pockets are one of the things that give flat roofs a bad reputation.
Flat roofs don’t leak. Poorly implemented flat roof penetrations leak. Most pitch pockets are poorly implemented roof penetrations. So follow these three rules:
Rule #1. Eliminate the need for any roof penetrations whatsoever.
Rule #2. When you fail at implementing Rule #1, exercise control over how roof penetrations are made by making the roofer responsible for them. Never, ever allow the M/E trades to do “roofing”.
Rule #3. Always show the roofing contractor what you want, so you don’t get a last century pitch pocket solution.
A Pitch Pocket is the last resort for sealing a roof penetration. When you have exhausted every possibility for accommodating a roof penetration in a more fool-proof way, a pitch pocket is the solution.
A pitch pocket is simply a sheet metal sleeve flashed into the roofingmembrane. The penetrating object, say a small angle, penetrates the roof membrane through the sleeve; and the sleeve is filled with a flowable, permanently mastic material to seal around the penetration. Originally this mastic material was wood resin, or pitch; ergo the name.
The reason a pitch pocket is a last resort is that nothing will maintain the seal forever in all types of weather. So you have just created an eventual leak. Yearly maintenance is required to avoid the leak.
The preferred solution is to penetrate the roof with a shape that can be easily flashed. Then transition to the irregular shape above the flashing. Equipment support frames are often done this way.
Another alternative to a pitch pocket for small items like conduit is a 'Pipe Box'.
COMMENTS:
This detail is suggested to specify the configuration, construction and materials required for a pitch pocket.
This detail can eliminate the need for specifications covering these conditions.
This detail is referenced on the roof plan.
The detail should be modified to show the actual type of roofing on the project.
You may want a specification covering the quality and installation aspects of these materials.
These details should be placed on the Exterior Detail sheets, the A-600 series of sheets per the National CAD Standards, contrary to the designation shown here.
Download PDF of detail.
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