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INSTALLATION FEATURE STORM-RESISTANT CONSTRUCTION


This Treasure Coast Farms riding arena in Florida is strengthened with storm- resistant construction. (Photo courtesy of MBMI Metal Buildings)


This building in Sweden was exported and designed for high snow loads. (Photo courtesy of MBMI Metal Buildings)


low point, the volume of falling waterfall can wash away the soil. The spacing of gutters can be decreased to


increase to load that gutters can resist, a common practice in regions with high snow loads. Steve Bradley Sr., national operations manager of special- ty products at Englert, recommends hidden hanger spacing 24 inches on-center for a gutter. “But in high winds and heavy snow load areas where a building may face stress, it is recommended that the hangers be spaced every 16 inches to prevent problems with gutters,” he says. For best drainage, gutters and downspouts must be kept clean. Modern reinforced wall louvers, built to meet


local building codes, can help minimize storm effects. “Adjustable louvers can be closed in the event of heavy rain, allowing zero water entrance from rain,” says Blake Edgeworth, vice president of sales and marketing, Moffi tt Corp., Jacksonville Beach, Fla. “Alternatively, fi xed louvers can be placed in locations with different rain and wind loads. While they don't close completely, they are designed for maximum water diversion.” The importance of properly installed roof curbs


cannot be understated. “The best roofi ng job can be made worthless if the openings for roof ventila- tors and exhaust fans are not properly installed,” Edgeworth says. “Furthermore, having the right curb caps and/or dampers is a must for any proj- ect. Getting input from a professional with experi- ence in ventilation is crucial to having a watertight, weatherproof building.”


Windows and doors In addition to straight-forward load paths and impene- trable roofs, it’s also important to protect buildings by installing storm shutters or impact-resistant windows. Some building codes require them in areas where wind speeds are 120 miles per hour or higher. Violent windstorms can hurl objects and fl ying debris that act like bullets and missiles that can break windows and damage building envelopes.


42 METAL CONSTRUCTION NEWS May 2013


Permanent or removable shutters reduce forces


on buildings and minimize water- and wind-related damages to the interior by protecting windows. Al- though the negative pressure caused by high-velocity wind fl owing over a building roof can cause the roof to fail with the building envelope intact, broken win- dows allow the air pressure to rise inside a building, creating an even greater pressure difference, and increasing the likelihood of roof failure. When struck by objects, impact-resistant glass may crack or shat- ter, but the fragments stay in place. Shutters are usually constructed from steel,


aluminum and polycarbonate. They can be affi xed to the outside of a building with screws, hurricane clips or a track system. Advanced shutters can be motorized and may even fold away when not in use. West Palm Beach, Fla.-based Armor Screen’s Wind, Rain & Impact Abatement System is a fl ex- ible, transparent membrane designed to withstand strong hurricane winds without rupture while defl ecting large and small projectiles. Impact-resistant doors can also withstand


wind-born projectiles. Outward-swinging doors reduce the likelihood of system failure in high wind. Garage doors in metal commercial buildings often fail in storms due to their large size and relatively weak material. In the past, wind-resistant garage doors required vertical bracing, which had to be manually installed prior to a wind event. Most door manufacturers now offer impact-resistant doors that do not require vertical bracing, which makes them much more convenient, and can even stand up to workplace accidents like forklift abuse.


Roofs and snow The steeper the pitch of the roof, the more easily a steel building sheds snow and rainy downpours from storms. “When it comes to severe weather affecting metal buildings, the greatest concern is that the building was designed for the proper loads,” says Strompf. “When it comes to snow, however, the concern is that if the building cannot


carry the weight of the snow, it could come crash- ing down. Adding more purlins on the roof is the best way to deal with this scenario. For snow, add- ing more gutter support straps and using a heavier gauge steel will help, but unfortunately, heavy snow will always bring down gutters.” “There is a why when you go to a ski resort,


you see a lot of metal roofs,” Buchinger says. “They are good at shedding the ice and snow with- out damaging the roof in many cases. Sometimes people use a southern-style gutter, that’s when the outside face of the gutter sticks out high than the pan of the roof panel. This hides the end of the panel seam. It’s great down south, it makes the roof look better a lot of times. Up north, that gutter will stop ice and snow for a little while, but then that ice and snow will tear that gutter off.” Many roof collapses are due to snow collect-


ing on a fl at or low-pitched roof. A more steeply pitched roof is easier to clear because gravity does most of the work. A roof slope between 12 and 14 degrees is desirable. However, the lower the building, the less the wind intensity and the less the area on which it acts, so the extra height of a high-sloped roof must be taken into account. While lighter roofs are more effi cient in warm


regions, dark roofs are the better choice in areas where there is a high likelihood of heavy snow- storms. Dark roof coatings absorb heat and help melt the snow more quickly and effi ciently. Overall, one of the best approaches for storm


readiness and its elements is to design the metal building system according to the local building codes and then install the systems correctly. “It is both expensive and time-consuming to go back and make a building storm-ready during installation or after the building is completed,” Henry says. “Every project should be built to the existing codes at the time of installation, which takes into consideration extreme weather conditions. Following building codes is the best defense against the worst-case scenario as far as weather is concerned.”


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