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Roof Pitch Pocket 101: What Roof Pitch Does and How to Install It

As your primary protection against the elements, your roof needs to have the best structural integrity and weather resistance that it can possibly provide. However, any form of penetration going through a roof, such as a chimney or other structure, can put this at risk. 

Source: architekwiki.com

For this reason, counter flashing measures such as roof pitch pockets are always installed to compensate for this. The pitch pocket is a type of roof flashing that is used on sloping as well as flat roofs to provide a watertight seal around roof penetrations such as columns. 

But how does a roof pitch pocket work? Why exactly do you need one? And how is it installed on a roof?

Learn everything about a roof pitch pocket in our guide.

What Is a Pitch Pocket on a Roof?

Source: bbsheetmetal.com

When it comes to typical roof penetrations, watertight protection is provided by metal boots or pipe sleeves made of metal. However, these solutions may not fit all possible use cases. 

Should a leak form around this, moisture will be able to seep through the penetration and reach the delicate insulation and framework that are located under the roof membrane, which may result in rotting, mildew, and other issues with the roof. 

It is during these situations that specialty flashing like pitch pockets are necessary.

How Does Pitch Pocket Work?

Simply put, a pitch pocket (also called a pitch pan pocket) is really just a simple sleeve that is flashed into the roofing membrane. The roof membrane is pierced by the roof penetration, and the sleeve is then filled with a flowable and permanently mastic substance to seal around the penetration. This mastic compound was originally wood resin or pitch, which is where the term comes from.

Pitch pockets are often constructed out of sheet metal, such as aluminum or steel, and resemble a top hat in shape. The vertical part of the pocket serves to cup around the roof penetration to collect the sealant while the horizontal flanges are there to maximize the contact area that the pocket has with the roof, securing its position. 

In order to further guard against leaks, pitch pockets are frequently combined with a storm collar or some other kind of counterflashing. The storm collar is designed to wrap snugly around the pipe’s diameter, and it extends outward from the device’s base to provide coverage for the device’s top. 

The storm collar should have a length that is sufficient to completely cover the rim of the pitch pocket, and it should have a width that is sufficient to ensure that any rain or moisture that does fall on the roof does so well outside of the flashing.

Do You Need a Roof Pitch Pocket?

From a general standpoint, you should always have some form of weatherproofing to cover any potential leaks that may be created by penetrations on your roof, which can include chimneys, HVAC vents, skylights, and others. 

However, a pitch pocket is generally considered by builders to be a last resort when trying to seal a penetration in your roof. The reason for this is that it is impossible for anything to keep the seal permanently in all kinds of weather—all seals will eventually deteriorate given enough time. 

What the pitch pocket has effectively become is a roof leak waiting to happen—in fact, roof pitch pockets actually need to have their seals replaced every year or so to keep it from leaking. That being said, using a pitch pocket does still have its benefits:

  • Greater flexibility. Having a pitch pocket allows you to weatherproof roof penetrations that can’t be done using more conventional methods, if not avoided entirely. This is especially true when the pitch pocket roof penetration is set at an awkward angle, has an unusual shape, or has a non-standard size that the aforementioned solutions cannot account for.
  • Provides roof support. Although roof penetrations that need pitch pockets are usually avoided, they can actually be beneficial in some cases as the roof penetration can give the roof additional support that wouldn’t otherwise be possible if the penetration was avoided. 
  • Easy installation. Compared to other roof penetration flashing solutions, a pitch pocket is very easy to install, which is due in part to its simple structure. The added flexibility gained from this allows it to be used in all of the ways that standard flashing cannot. 

How To Install Roof Pitch Pocket

As noted earlier, the process for installing a roof pitch pocket is quite easy and only takes a few steps, which are as follows:

  1. Place a nail or some other marker around the protrusion while you are working on a re-roofing job that involves installing a metal pitch pocket. 
  1. Take off any foam insulation in your roof penetration up to a point higher than the level that you will pour your mastic sealer up to. 
  1. Clean your roof penetration and apply contact cement or some other appropriate adhesive to it so that it extends past the line where the sealer will be poured into. This will make sure that your sealer will make proper contact with the penetration and create a strong and lasting seal.
  1. Attach a waterproofing membrane (the standard material of choice is usually EPDM) to the roof so that it covers the roof penetration and extends beyond it. 
  1. Apply a small amount of mastic at the base of the pitch pocket, then attach the pitch pocket to the roof, holding until the pitch pocket has adhered to the surface.
  1. Apply flashing in the pitch pocket with both cured and uncured flashing such that it extends over the top and goes into the pitch pocket. 
  1. Prepare your pourable sealer of choice, which can be flashing cement, tar pitch, or asphalt mastic. 
  2. Pour your sealer into the pitch pocket, making sure to fill the pocket just under the brim. Depending on the application, you will want to account for the slope of the roof and apply more or less of the mastic to make sure that it does not spill over.

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