Pitch Pans (Pitch Pockets): Roof Flashing Explained

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A group of large pitch pans on a PVC roof provide a seal around angled equipment supports.
Galvanized steel pitch pan on a built-up roof with various conduit penetrations.

Pictures of Pitch Pans

Pitch Pans: Basic Information

Other Terms for Pitch Pans

Pitch pans are also called pitch pockets, penetration pockets, pitch boxes, or sealant pockets.

What is a Pitch Pan?

A pitch pan is a type of roof flashing for small or irregular roof penetrations.

Pitch pans look like boxes, rings, or cylinders made out of sheet metal (normally galvanized steel) or a pre-molded polymer. Although they are usually open at the top, some specifiers require pitch pans to have covers on them for added weather protection.

Pitch pans function as containers for the relatively large amount of sealant required to seal these small or irregular roof penetrations.

What Pitch Pans are Used For

Pitch pans are used to flash roof penetrations which would be difficult to flash in any other way: small penetrations such as electrical conduits, irregularly-shaped penetrations such as I-beam supports, or multiple small penetrations very close together.

Types of Sealant Used with Pitch Pans

The type of sealant used in a pitch pan depends on the type of roof system the pitch pan is a part of. The sealant has to be compatible with the roofing material, or it will not bond properly and the seal will fail.

Pitch pans on single-ply roofs like EPDM, PVC, or TPO require special pourable sealants formulated to work with that system.

After the sealant container is opened, the sealant is poured into the pitch pan and then hardens. The roofing system manufacturer will either provide the sealant or specify which one to use.

Pitch pans on asphalt roofs typical use asphalt cutback mastic, or roofing cement, which is basically asphalt mixed with mineral spirits.

This material is soft out of the bucket and easily packed into the pitch pan with a trowel. After being exposed to the air it hardens in place.

Problems with Pitch Pans

Pitch pans are notorious as a source of leaks. Sealant shrinks and degrades over time, leading to eventual leaks. The item being flashed by the pitch pan may vibrate or shift in the wind and break the seal, especially as the sealant gets older.

The relatively small flange commonly found on metal pitch pans makes it difficult to provide an adequate tie-in with the roof membrane; failed stripping is another source of leaks at pitch pans.

Pitch Pans and Roof Maintenance

Because of these issues, pitch pans should be a high priority during preventative maintenance inspections, and should be checked twice a year. Inadequate sealant should be topped off immediately.

Don’t Use Pitch Pans if You Don’t Have To

A pitch pan should be considered a flashing of last resort. At curbed HVAC units, conduit lines should be routed down into the building inside the curb, underneath the unit, if possible. A gooseneck penetration flashing is preferable to a pitch pan, and can accommodate flexible conduits or cables.

Construction detail for a pitch pan to be installed on an EPDM roof.
Construction detail for a pitch pan to be installed on an EPDM roof.

1. General: For a look at some retail-available prefabricated pitch pockets, see these pitch pockets on Amazon, or this page at the Home Depot.*

2. General: “Manual Elements: Penetration Pockets” is a short, decent introduction to pitch pans. From 2005, archived on the Professional Roofing magazine website.

3. General: Reasonable concerns and advice regarding pitch pockets can be seen over on Architekwiki. Don’t let “Pitch Pockets” scare you too much.

4. Building Codes: Pitch pans are not specifically mentioned in the model building codes of the International Code Council, but they are broadly covered by 1503.2 Flashing in the International Building Code and R903.2 Flashing in the International Residential Code. To see language in a building code that has been amended to mention pitch pans specifically, see 1514.2.5 Roof Penetration Flashing from the 2017 Florida Building Code.

5. Technical: See this product data bulletin for assembly and installation instructions for basic galvanized steel pitch pans. On the R. M. Lucas Co. website.

6. Technical: See this product data sheet for technical information about precast, non-sheet-metal (in this case, polyester resin) pitch pockets. On the Chem Link website.

7. Technical: See this product data sheet for technical information about pitch pans made from injection-molded TPO, intended for use with TPO roof systems.On the Johns Manville website.