What Is a Pitch Pocket and Why Does It Matter?
Pitch pockets are essential for sealing rooftop penetrations, especially on flat and low-slope roofs. Whether it’s a pipe, power cable, or thermostat wire passing through your roof membrane, these elements need to be properly sealed to prevent leaks. Pitch pockets act like containment trays, holding pourable sealant that surrounds each element for a watertight seal. Unfortunately, many mechanical and electrical contractors don’t always follow proper rooftop practices, which can lead to costly roof damage down the line. That’s why understanding pitch pockets — and using them correctly — is key to maintaining a durable roofing system.
Sealing Equipment Penetrations With Pitch Pockets
The picture below shows an example of a pitch pocket which seals the penetration of a schedule 40 steel screwpipe gas line through a low-slope TPO roof membrane. The same pitch pocket also seals the power cable and the thermostatic control wiring. Because these smaller diameter and different shape elements are also installed at the same location, the nature of a pitch pocket is extremely helpful. A pitch pocket, as it works as a tray to contain and restrain a liquid applied sealant, allows the liquid sealant to seal a variety of different shapes of elements. (Pitch pockets can be so effective in this way, that one of the only viable alternatives available is the installation of a gooseneck type sleeve.)
The picture below shows the same pitch pocket, more closely. A pourable sealant has been applied to fill the top of the pitch pocket and surround the elements which pass through the rooftop penetration. The pitch pocket itself essentially forms a tray that will retain this liquid application of sealant so that it can the applied in a way where it surrounds the pipe and all other elements. Some of these elements are relatively small and simply applying gun applied sealant at the penetration of those smaller elements would be insufficient and would not be self supporting and avoid damage or deterioration over time. Overtime because of thermal expansion and many other conditions, such as vibration, the pipes and wires and other elements will move differently away from and against the roof membrane. A pitch pocket seals between those disparate elements to seal in a unique way.
In the next picture below you can see that there are a total of four different types of elements that are provided to or conveyed from and away from the packaged heating and air conditioning system. This type of HVAC unit is similar to split systems but happens to be an all-in-one unit that provides both heat and cooling and includes the fan which pressurizes the ductwork as well. All-in-one units like this can be installed on a curb or installed on steel beams that span the building from side to side and bare on the parapet walls. The parapet walls, in the case of most rowhomes and row buildings, provide a structural path at the shortest principle span in the building. (The rear ell and circumstances of corner bracing may be exceptions and actually provide shorter spans, but these areas are often less centrally located and therefore not conducive to air distribution.)
In the next picture below, you can clearly see the elements that are sealed by this pitch pocket: the oxidized metal pipe is a gas line, the larger wire is the power cable, and the thinner wire is the thermostatic control cable.
Maintaining A Modern Roofing System
Smart proactive replacement, construction, upkeep and maintenance of low slope roof systems requires an enthusiastic interest and understanding of waterproofing principles and building science. Here in Washington DC, historic and modern residential and commercial buildings are extremely expensive and the roof and related systems provide the shield that preserves the building.
FAQ Section (Add this near the bottom of the post):
❓ What is a pitch pocket on a roof?
A pitch pocket is a metal container installed around roof penetrations like pipes and wires. It’s filled with sealant to create a waterproof barrier that protects the roof from leaks.
❓ Why are pitch pockets important in roofing?
Pitch pockets help seal complex or irregularly shaped rooftop penetrations that traditional flashing can’t cover. They’re especially useful for flat or low-slope roofing systems.
❓ Are pitch pockets used in residential roofs?
Yes, pitch pockets are used in both commercial and residential roofing — particularly on flat or low-slope roofs where penetrations are common for HVAC, gas, or electrical systems.
❓ Can I seal a roof penetration without a pitch pocket?
In some cases, alternative methods like gooseneck sleeves can be used, but pitch pockets remain one of the most effective solutions for varied shapes and sizes of rooftop elements.
We encourage all of our clients, and all readers of this article and to our blog in general, to prioritize the value of quality construction and building maintenance, and develop a relationship with our company. You can learn a lot more on our blog. Feel free to check it out. If you have questions about the roof and related systems of your building in Washington DC, fill out the webform below and drop us a line. We will be in touch if we can help.
