Matthew Leonard, Vice President, Architectural Sheet Metal Inc.
Metal is one of the oldest types of roofing material, in use thousands of years ago in Asia and Europe. There are metal roofs on buildings today that are hundreds of years old. Copper is one of the first known metals used for roofing, dating from around 970 B.C. Over the centuries, the types of metal and the way they have been used has drastically changed to fit the needs and wants of the building designers and owners. It has been tested through time and remains a popular material. Today, metal roofing is getting a big boost from the green building movement because it is 100 percent recyclable.
In today's roofing world there is a metal roof system that can fit just about any size and shape building. These systems range from the most common corrugated and standing seam roof panels to custom styles that look like other types of roofing, such as tile, shingle or slate. Metal is installed on buildings from large airports and schools to the very small accent roofs on houses and commercial buildings.
Steel is the most cost-effective metal. The most common thickness is 26 ga. (steel is measured in "gauges," abbreviated "ga." where the smaller the number, the thicker the metal). Many locations, to meet wind uplift requirements, will use 22 ga. or 24 ga. Steel will rust, so it needs a protective coating. Commonly used coatings include Galvalume (zinc/aluminum mix), Galvanized and Kynar/Hylar (painted). The paint used today has come a long way and it will provide 20 or more years of high-quality finish color.
Aluminum demand has been growing as a metal roofing component due to its great weatherability and corrosion resistance in areas along saltwater coast lines. It is a softer material than steel and will expand and contract better than steel. Because of aluminum's inherent characteristics as an element, it doesn't require special coatings to resist deterioration from salt. For most people, however, the bare-metal look isn't desirable. It can be painted with the same Kynar/Hylar finishes as steel. In fact, most manufacturers don't recommend or won't sell bare aluminum roofing panels since non-uniform weathering cannot be avoided or controlled. Aluminum is measured in decimal inches (the larger the number, the thicker the material) and the most common thicknesses for metal roofing panels are .032 inches and .040 inches.
Copper is possibly one of the oldest metals used for roofing; it is a great metal to use bare in almost any location. When using copper, you must be mindful of its expansion and contraction properties, as well as other metals it comes into contact with. There are many other metals that cannot come into contact with copper. Even water runoff from an upper copper roof to a lower roof of another type of metal may be an issue. One of the biggest downsides to copper is its upfront cost, but when life-cycle cost is considered, it becomes more cost-effective for the building owner. The price of copper is like a rollercoaster and is expensive when compared to the upfront cost of steel or aluminum. Copper has the ability to patina (produce a film thru oxidization that protects the metal) which will, over time, change the metal from a bright shiny orange/brown color to a dull brown, to finally a light greenish color (the Statue of Liberty is
made of copper.) One of the many advantages of copper is it is soft and easy to bend and fold, making it great for roofs that steel and aluminum just can't fit. Copper is measured by weight per square foot, commonly 16 or 20 ounces.
Other less common metals include zinc, terne coated steel, stainless and lead coated copper.
Standing seam metal roofing (SSMR) is a widely used style that allows for an architectural or structural panel. Depending on the location, design of the roof and desired aesthetics, an architect can select from many different panel profiles for the kind of metal and color they want. Most standing seam metal roofs (SSMR) are made of 26 ga. steel for its value and strength. With a standing seam roof the panel will have a flat (pan) area that covers the building and
two vertical legs that allow for over lapping of each adjacent panel for water shedding or waterproofing. Depending on the panel, the vertical legs (or highs) will be either a "snap lock" or a "mechanically seamed" panel. The snap lock allows for quick install and goes together much as a tongue-and-groove floor would. The mechanically seamed panel will use a machine to bend the seam formed by the two panels together and will be stronger than the snap lock system. Also, there will be no exposed fasteners, so each panel will be attached to the decking or supports with a concealed clip. Limiting the exposed fasteners provides a cleaner look and reduces the risk of leaks around the penetrations.
Exposed-fastener roofs are what many people think of when they think about metal roofs. These types of roofs will have a large metal sheet that has a type of corrugation or high spots that give the panels their strength. There are many different profiles that fit this category, but most will be installed similarly and have fasteners on the top side of the panels, exposed, with special neoprene or rubber backed washers to protect the screw holes from water.
Special profile metals are something that many people don't realize are an option. In areas where either shingle or tile roofs are required, the benefits of metal with the look of either shingle or tile roofs are available in various sizes, shapes and colors. For years, manufacturers have been able to apply a stone coating to the metal to make it look and feel like shingles.
Years ago, maintaining safety during metal installation was a challenge. Today however, with all of the new safety devices available, there isn't a metal roof that one cannot tie-off on. There are many options that allow installers to clamp to the highs of a standing seam roof or a permanent anchor on an exposed fastener. There is no excuse for not being safe and following OSHA's guidelines.
Tools of the trade are always the key to a successful project. When working with metal, a few must-have items include tin snips (metal cutting scissors), hammers and wide flange benders (duck bills). Coming to the job each day with the right tools will make all the difference in how the day goes, as well as being perceived as a professional by those around you.
Metal roofing is a specialty and one that can give a great sense of accomplishment when doing artistic custom fabrications or large-scale buildings. Learning to work with metal takes time but, when mastered, it can be used in many challenging ways and will always keep one interested.
Matthew Leonard, Vice President, Architectural Sheet Metal Inc., Orlando. Matthew serves on FRSA's Board of Directors, Chairs the Worker Training Subcommittee is a member of the Young Professionals Council, 'Building, Codes, Membership, Governmental Affairs and the Convention Committees. He also serves as the President of NRCA's National Roofing Legal Resources Center, is a member of the CFRSA Affiliate and of the Professional Construction Estimators Association.
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