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Understanding Metal Roofs
Metal roofs, aluminum, steel, copper, terne, zinc July 28, 2009
Hello. This is Greg Zimmerman, executive editor of Building Operating Management magazine.
Today’s topic is about the types of metals used in commercial metal roofs.
There are five main types of metals facility executives can choose, based on the specific criteria of their buildings.
The two most common are aluminum and steel. The majority of commercial metal roofs are made of steel, especially flat or nearly flat roofs, as well as the architectural standing seam products that are used on steep slope applications. Steel roofs come in various gauges – as the gauge number goes down, the steel is thicker. Common gauges for steel metal roofs range from 22 to 16 gauge.
Aluminum is a good choice for coastal environments because it won’t corrode. It’s lightweight, recyclable, and most manufacturers use a high percentage of recycled content in their roofing products. Because aluminum is soft and easily bendable, it is available in dozens of different commercial profiles and colors – including shakes, shingles and standard standing seam.
The more exotic metals sometimes used in specialty applications for roofs are copper, zinc and terne. Copper is a striking metal that’s been used on roofs for centuries. While copper is the most expensive of these five, it can usually last for hundreds of years. It weathers over time from its shiny salmon color into an attractive bluish/green patina.
Terne metal is steel or stainless steel coated with an alloy of mainly zinc and tin. Terne is very corrosion-resistant, even in marine environments. Zinc roofing is relatively new to the U.S., but is gaining momentum because it is has environmental benefits. It occurs naturally, and water runoff from a zinc roof is 100 percent clear, so it can be captured and reused. Zinc roofs have an expected life span of 60 to 100 years. Many are drawn to the rich gray color which deepens over time.