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tors, metal plates, straps and anchor bolts. They should be made of stainless or double hot-dipped galvanized steel to prevent corrosion. They come in many shapes and styles, allowing them to be used in different situations. Generally speaking, any reinforcing of the


metal roof, wall and structural framing systems are addressed at the design stage. “Engineers have several ways to account for forces due to storms,” says Mark Henry, senior research engineer at But- ler Manufacturing, Kansas City, Mo. “The strategy is to design the building for storm loads, rather than strengthening or reinforcing the metal roof systems during installation. For instance, during the design stage, the engineer may increase the thickness of the roof panel or increase the number of roof purlins to account for storm forces. Butler Manufacturing offers proprietary roof-panel clips and seam-reinforcing clamps that can be speci- fi ed by the engineer to enhance the wind uplift resistance of the metal roof system. Engineers may choose to increase the panel thickness and/ or increase the number of wall girts of exterior wall panels to resist the storm wind forces.” “In order to strengthen a metal building so that it


will be able to survive severe winds, you would need to beef up purlins and girts, that is adding more girts along the walls and more purlins on the roof,” says Ian Strompf, president, MBMI Steel Buildings, Delray Beach, Fla. “Adding more screws to all the sheeting will also strengthen the building for heavy winds. Reinforcing roofs, extra caulking, and more gutter straps and clips will all help to add strength to a metal building, but if the rest of the building is not properly prepared, they will not be very useful.” “The roofi ng contractor must furnish and


supply a metal roof, and should be very concerned


about storm-resistant construction,” says Ken Buchinger, vice president of business development and R&D, MBCI, Houston. “The roofi ng contractors are free to order components and it is incumbent on them to understand the engineering behind the panels, choose the proper accessories, and use the right fasteners and screws to attach the structure. There is nothing stopping them from ordering one of our standing seam roofs and not ordering the right clips. They could order no clips and simply screw it down like a through-fastened panel instead of clip- ping it down like it was designed to be.”


Water warning Wind damage accounts for only a fraction of a building’s storm-related destruction. More fre- quently, it’s water infi ltration, not wind, that causes most storm-related damage. “Water penetration through or around otherwise intact openings from wind-driven rain can do a signifi cant amount of physical damage, cause occupant displacement and business interruptions, and lead to extensive restoration expenses,” cautions Dean Lewis, educational and technical information manager, American Architectural Manufacturers Association, Schaumburg, Ill. “It can also create a mold-friendly environment in unseen wall cavities and in spaces between exterior sheathing and cladding.” Fortunately, according to Henry, wind-driven


rain is usually not an issue for metal roof systems. “They are designed to be weathertight,” he says. “The long interlocking roof panels do not provide a gap through which wind could drive rain into the building interior. Metal roof systems that have been approved by Miami-Dade County—such as Butler Manufacturing’s MR-24 Roof System—must pass a static water head test to demonstrate their


This Florida Keys building in Marathon, Fla., is designed with storm-resistant construction to best handle hurricane winds. (Photo courtesy of MBMI Metal Buildings)


resistance to rain forces.” With metal roofi ng the weak spot could be a poor weld, a rusted panel or a screw that’s backed out. “The metal standing seam roofi ng material


you choose is always an issue,” says Joe Tripod, director of technical services, Englert Inc., Perth Amboy, N.J. “Some, not all, metal roofi ng products meet industry requirements, such as the Florida Building Code wind-uplift requirement, Miami Dade uplift testing, FM uplift testing, UL Uplift Standard 580 and ASTM 1592 uplift standards. These products, like Englert’s Series 1300 and Series 2000 standing seam panels, have gone through rigorous, controlled performance examina- tions that make them more qualifi ed than others to withstand the onslaught of Mother Nature. But a sturdy product makes up only one aspect of a hur- ricane resistant roof.” Tripod argues the soundest defense against the fury of Mother Nature should also consider the following: • an American Society of Consulting Engineers (ASCE) analysis to specify the most storm proof construction plan to withstand hurricane force winds for a specifi c building,


• a weather-tightness warranty from the roofi ng material manufacturer with on-site installation inspections,


• and the services of a certifi ed installation contractor who will properly install the roof following the instructions of the ASCE analysis.


Gutters, louvers, curbs Gutters and downspouts protect buildings in storms by quickly channeling excess water away from the building and the foundation. Gutters should be designed so that they overfl ow out- wards for the full length. If they overfl ow only at a


This New Orleans Saints practice facility is a Butler building that withstood Hurricane Katrina in 2005 and served as a headquarters for rescue personnel. (Photo courtesy of Butler Manufacturing)


www.metalconstructionnews.com


May 2013


METAL CONSTRUCTION NEWS 41


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