Combining functionality and aesthetics, metal roofing is a great option for residential and commercial buildings alike. It is light weight and high strength, providing wind resistance and longevity to a roof. When properly designed, metal roofs can even withstand hurricane force winds. They are thoroughly tested in order to meet standards set by the American Society for Testing and Materials (ASTM).
“If it is installed correctly and you use the right metal roof system with the right structure, it will stay on during hurricane force winds and help keep the weather out,” says Mark Silva, VP Roofing Sales, Kloeckner Metals Corporation. “Our roofing systems, the clips, the screws, the panels, and the way the panels interlock with each other, are all factory tested to pressures from 100 up to 200 pounds per square foot.”
The material is made corrosion resistant by utilizing a galvalume finish. While normal galvanization involves a hot-dip bath in zinc, galvalume combines zinc and aluminum with small amounts of silicone. This increases corrosion resistance, whether the concern is salt or industrial byproduct.
“The corrosion resistance of aluminum is complimented by the preferential corrosion of zinc, giving the Galvalume finish the best of both worlds. In other words, the zinc helps reduce corrosion at the cut edge and deep scratches,” Silva says. “The aluminum, on the other hand, will help with the overall corrosion resistance of the roofing panels.”
Another layer of protection is provided by the paint system that is then applied to the metal roof. Factory paint systems can last for 20 years, and they can serve the dual purpose of energy efficiency. In addition to the natural ability of the metal to dissipate heat quickly, an ULTRA-Cool® paint system can be applied to the surface. The high solar reflectance of the paint material can even be energy star certified.
Metal roofs also have the ability to be easily outfitted with photovoltaic systems, to capture solar energy. The systems can be clamped onto the roof without having to penetrate the metal. The slope of the roof helps eliminates the need for creating an artificial slope for the solar panels, and it saves space.
“You get the photovoltaics off the ground and onto the roof with a good strong attachment to the metal roof,” Silva says. “If properly installed using S-5! clamps, the solar system won’t harm the metal roof at all and will add a bit to wind resistance, believe it or not.”
Metal roofs are also frequently used for water catchment systems, though no manufacturer officially sanctions them for such a use. The main danger comes from debris that may land on the roof and leech into the water, as opposed to the roof itself.
“The paint systems don’t have anything inherently dangerous,” Silva says. “The galvalume coating doesn’t either, but if used, everybody would recommend you use a reverse osmosis filter at a minimum if you are using it for water catchment.”
Standing seam metal roofs are extremely water tight. They are attached to the roof structure by concealed clips and to each other by electric seaming or, more commonly, an integrated snap lock system.
“You don’t have any screws penetrating the roof, and so you have less likelihood of leaks,” Silva says.
Ultimately, the quality of the metal roof will be dependent on the quality of the parts involved. Different grades of steel are available for different demands. Galvalume also comes in grades, which will determine the thickness and, in turn, durability of the coating. The same can be said of the paint systems.
“The components you purchase with the roof system matter,” Silva says. “A low quality roof may use a polyester type paint system, or silicone-modified polyester, whereas a high end roof will utilize a Kynar 500® paint system. The best systems will be coated with ULTRA-Cool® Kynar paint system.”
Maintenance on metal roofing is simple. For high pitch roofs, virtually no maintenance will be required. Low pitch roofs should be given a fresh-water wash annually or semi-annually to get rid of any debris that may become attached. Other than that, the roof should last a very long time on its own. This longevity and durability make metal roofs particularly desirable, especially when taken together with the other benefits.