Consider Standing-seam Metal Roofing When Seeking Long-term Performance and Sustainability

Metal panels can be installed to a roof slope as low as 1/4-in-12, with the ability to obtain material warranties for the base Galvalume-coated metal materials for more than 20 years. In fact, based on a scientific evaluation of Galvalume metal roofs, the life expectancy of this roofing panel is well over 20 years. This was evaluated in a 2012 study sponsored by the Chicago-based Metal Construction Association and Zinc Aluminum Coaters Association, Olympia, Wash. The study included forensic tests
at 14 existing Galvalume standing-seam metal roof sites around the U.S. with the average age of these roofs at more than 30 years at the time of testing.


A retrofit metal roof installed in 2014 at Narrows Elementary/Middle School, Narrows, Va., has a 1/4-in-12 slope. The existing school building was constructed with a flat roof in 1932.

The testing of these metal roofs, installed at slopes as low as 1/4-in-12, provided metallurgic results that proved these roofs will perform well over the 60 years expected by USGBC. (Access the study’s full report.) Photo 1 shows a Galvalume metal roof that was part of the Galvalume study, installed at an industrial plant in Mansfield, Ohio. This roof had performed without repair or removal for more than 32 years at the time of the study.

The perception that metal roofs will only perform for about 20 years and they need to be sloped at 2- to 4-in-12 is not true. A properly designed and installed standing- seam metal roof, whether new or retrofit, can be installed at IBC’s minimum slope of 1/4-in- 12 and is expected to last well over 60 years.

Existing Building Code

Building codes are kind to metal roofing. For example, metal retrofit roofs that load the existing building structure with light-gauge steel framing are exempt from the require- ment of removing the existing roofs. In the 2018 version of the Existing Building Code, in situations where there are two or more existing roof coverings, the existing roof coverings are to be removed prior to the installation of a new roof membrane with one exception: “Complete and separate roofing systems, such as standing-seam metal roof systems, that are designed to transmit the roof loads directly to the building’s structural system and that do not rely on existing roofs and roof coverings for support, shall not require the removal of existing roof coverings.” This exception language has been in all versions of IBC since the first version in 1997.

In addition, because a metal retrofit system is considered a recovery roof, as opposed to a replacement roof, it is not required to include an upgrade of the insulation system to meet the current values established by the International Energy Code.


An abandoned hospital in Pearisburg, Va., was converted into a modern sheriff’s and emergency services facility in 2016. A metal retrofit roof was installed on teh building.

Consider Metal Roofing

When considering the roofing portion of public building infrastructure, a standing-seam metal roof—when designed and installed properly—can span a 60-year timeframe. A life-cycle cost analysis demonstrates a metal roof’s cost-effectiveness for all types of commercial and institutional buildings, including public schools, prisons, universities and other buildings funded with public money.

In addition, existing buildings’ roofs needing replacement or recovery, which account for approximately 75 percent of all public buildings, can be fitted with this type of roof—no matter the slope—with an approach that has been in existence for almost 40 years. Therefore, whether the public building is just being built or is in need of a retrofit roof, a standing-seam metal roof should be considered.

PHOTOS: Metal Roof Consultants Inc.

About the Author

Chuck Howard, P.E.
Chuck Howard, P.E., is owner of Metal Roof Consultants Inc., Cary, N.C., and has more than 30 years’ experience providing commercial metal roof consulting and engineering.

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