The Many Attributes of Metal Roofing

by Jonathan McGaha | June 30, 2013 12:00 am

Metal roofing is becoming extremely popular, in many instances, due to the wide variety of panel profiles, widths and colors. Certainly metal roofing allows designers to incorporate the aesthetics of the roof into their overall building design instead of hiding it behind parapet walls. However, as beautiful as metal roofing is, there are many more reasons to consider a metal roof.

Metal roofing is one of the most durable roofing materials available. While through-fastened metal
roofing can be designed by section properties, standing seam metal roofing is designed from
load tables developed through testing per ASTM E1592. Either way, metal roofing can be designed
to withstand winds exceeding 150 mph, depending upon the panel profile and the substrate to which it
is attached. While wind resistance is an extremely important attribute, there are many others.

There are a number of designs for internal fire protection per UL 263 that provide for 3/4- to twohour
fire ratings. For external fire sources, metal roofing carries a UL Class A rating over open metal framing, i.e., purlins or joists. When used over solid deck with a UL approved barrier board or underlayment, metal will also achieve the Class A rating.

Metal roofing also carries the UL Class 4 rating for impact resistance, as tested by UL 2218, which
was designed to mimic the impact of hail. This is a particularly useful attribute in areas that regularly
experience hail.

Another attribute of metal roofing is its ability to accommodate temperature extremes. Many standing
seam metal roofs can be designed to handle wide variations in temperature through the use of
seam designs that allow unlimited thermal movement or through the use of special clips that allow
the roof to “float” as the roof panels expand and contract during temperature fluctuations. Cool roof
paint is now common which reflects a large portion of the sun’s energy back into the atmosphere,
reducing the “urban heat island effect.” In addition, on solid decks, an air cavity can be designed to
allow for “above sheathing ventilation.” This design incorporates air intake at the eave of the roof and air
exhaust at the ridge, allowing natural convection to cool the air cavity between the metal roof and the
subdeck.

The long service life of metal roofing is also of great importance, especially on buildings such as schools and local, state and federal buildings. Inspections performed on metal roofs 25 years and older reveal that metal roofing can be expected to perform for 50 years and longer. This is a huge sustainability issue, especially if one is considering installing a solar array on their roof. Since solar arrays should last 30 years or more, you want to make sure your roof will last at least as long. A building owner is not going to want to pay to remove the solar array, reroof and then reinstall the array.

Add to the above that metal roofing is typically made from 25 to 30 percent recycled material and at the end of its service life, is virtually 100 percent recyclable. All of this makes it is easy to understand why metal is becoming very popular as a roofing material. It is pretty, long lasting, resists wind, fire, hail, extreme temperatures and is sustainable.

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Ken Buchinger is the vice president of business development and R&D for Houston-based MBCI. To learn more, visit www.mbci.com[1].

Source URL: https://www.metalarchitecture.com/articles/the-many-attributes-of-metal-roofing/

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