Duct Supports - What Is The Proper Way To Support A Rooftop Duct?

By Author: Rwbecca.Franks
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If you have ever been up on a commercial roof (shopping center, school, office building, etc), odds are that you have seen HVAC ducts that are running across the top of the roof. These ducts are carrying air to a separate part of the building. For a number of reasons sometimes these ducts run across the top of the roof instead of below the roof. Because these ducts are made of metal, and because they run above the roof's surface, they need to be support up off of the roof so that the sharp metal does not puncture the roof's membrane. Have you ever really examined though, how these ducts are supported? That's the point of this article. Let's explore the topic: What do proper rooftop duct supports look like?

Majority of the time, a rooftop duct support is made of metal. This is a consistent element. The two things that are not consistent though, are the shape of the duct support and how it attaches to the roof. Let's explore these a little further:

1.The shape of a duct support: On many roofs you will find a duct support that was fabricated by the HVAC contractor. These duct supports often only support the bottom ...
... side of the duct. This is not sufficient because in high wind storms this will allow the duct supports to be blown laterally. The proper duct support should be and H-shape so that the bottom of the duct rests on the crossbar while the sides of the duct are contained by the upper legs of the H-shape thus preventing lateral motion.

2.How a duct attaches (or not) to the roof: Most cheap (improper) rooftop duct supports are made of angle iron and this angle iron penetrates the roof's surface and is attached to the structural metal of bottom side of the roof. While this makes them sturdy, this penetration in the roof often creates roof leaks and is thus undesirable. The proper way to support the duct, is by using a non-penetrating rooftop duct support. These supports have large heavy base plates that sit on top of the roof's surface for the vertical legs of the H-shape to attach into. These base plates do not penetrate the roof's surface but still provide a very strudy base for the duct support. By using this type of duct support base, your roof is free from the worry of leaks because of the penetration, and your ducts supports are as sturdy as ever.

To see an example of what a proper rooftop duct support looks like, be sure to visit www.RoofStuffinc.com.

Eric Hassfurther is the President and Founder of Dallas based RoofStuff, Inc (www.RoofStuffinc.com) a manufacturer of pipe supports, duct supports, and other rooftop accessories. RoofStuff, Inc was founded in 2002.