ZMAX Long-Life high-low threads and sharp cut point allows for holding power. ZMAX can be used with battery operated and impact screw guns. ZMAX alloy fasteners are engineered for corrosion applications. ZMAX offers a large outer diameter to prevent wind uplift and is suitable in snow load regions. The ZMAX Long-Life is ideal for coastal environments, preventing red rust on fastener heads once installed into metal buildings.
Tectura’s Lok Down system is a proprietary pedestal system for rooftop pavers. A top plate, made to match or contrast with the pavers, fits into a recess, allowing for a flush walking surface. Colored bolts then tighten the system together for a total rafted paving system. Lok Down is the only system backed by full-scale tests that simulate the effects hurricane conditions on rooftop paving products. The Lok Down system is tested to withstand wind speeds of more than 145 mph.
The BTI-Greensburg John Deere Dealership Installs Tornado-Resistant Daylighting Systems and Other Sustainable Materials
On the night of May 4, 2007, brothers Kelly and Mike Estes saw their BTI-Greensburg John Deere Dealership obliterated by an EF5 tornado nearly 2-miles wide (according to the Enhanced Fujita Scale, which rates the strength of tornados by the damage caused; view the scale on page 3). Astoundingly, 95 percent of their town—Greensburg, Kan.—was also destroyed that day. The tornado did much more than rip roofs off buildings and toss things around; it turned the entire community into what looked like kindling.
Rarely do communities get hit by an EF5 tornado, which can come about when air masses collide. Sometimes warm, humid air from the Gulf of Mexico rises above drier air from the Southwest deserts in the U.S. This can create unstable conditions resulting in thunderstorms and worse. A strong collision of air masses creates a strong storm. Additionally, wind patterns and the jet stream can magnify the storm, resulting in what people refer to as “the perfect storm”.Despite the large-scale losses incurred by the entire town, 100 customers and friends of the Estes family showed up the morning of May 5 to help them salvage what remained of their business. Shortly after the tornado disaster, Kansas Gov. Kathleen Sebelius stated her wish that Greensburg become the “the greenest city in the state”.
As part of their commitment to their community, Kelly, Mike and their family decided to rebuild their business in a better, greener way. They wanted the new 28,000-square-foot prefabricated metal building to be the world’s greenest farm-machinery facility; attain a LEED Platinum rating from the Washington, D.C.-based U.S. Green Building Council; and use the least energy possible. One of the most important considerations was using building materials that could withstand future tornados.
To help achieve LEED Platinum and outlast any future high-velocity winds, they incorporated 12 Daylighting Systems in their retail area’s roof to showcase their merchandise; reduce lighting energy costs; and flood the area with natural light, a benefit for customers and employees.
The Daylighting Systems capture light through a dome on the roof and channel it down through a highly reflective tube. This tubing is more efficient than a traditional drywall skylight shaft, which can lose over half of the potential light. The tubing fits between rafters and installs with no structural modification. At the ceiling level, a diffuser that resembles a recessed light fixture spreads the light evenly throughout the room.
The dome is made from high-quality acrylic resin that is specifically formulated for increased impact strength, chemical- and weather-resistance, and high clarity (a polycarbonate inner dome is used for high-velocity hurricane zones). Domes are engineered to deflect midday heat and maximize low-angle light capture. The tubing is made from puncture-proof aluminum sheet coated with the highly reflective material for maximum light transfer. The units (independently tested by Architectural Testing in Fresno, Calif.) comply with various building codes including the 2009 International Building Code and 2010 Florida Building Code, including high-velocity hurricane zones.
“When our power went out one time for four hours, we were able to keep the shop open and operating due to daylight strategies, which includes the Daylighting Systems,” notes Mike Estes. “We didn’t anticipate this benefit but we’re really happy to have this bonus.”
PHOTO: SOLATUBE INTERNATIONAL INC.
Wind damage to roof systems is often catastrophic, placing the building users at a life-safety risk, resulting in interior and furnishing damage and suspension of interior operations, loss of revenues, legal ramifications and great costs to repair. Because of my 30 years of experience in the design of roof systems and forensic investigation, I’m often called upon as an expert witness after wind events. In this article, I’ll review a couple wind-event roof failures, the causes of the failures and how they could have been prevented. I’ll also provide recommendations for failure prevention in the design process for new roof systems, as well as for existing roof systems.
The Perfect Storm
How can it be that when roof systems are to be designed for code-required wind-uplift resistance that so many fail in winds well below the design parameters and/or warranty coverage? The answer could be design-related, material or installation; typically, it involves all three.
Architects and some roof system designers are often not as knowledgeable about roof systems as they should be, have little empirical evidence in how all the components work together as a system, and move beyond their abilities (a violation of their standard of care) when designing roofs where specific detailing is required. In addition, manufacturers are all too often
bringing new products to the marketplace that have not been properly vetted in the field and their long-term performance is truly unknown. Unfortunately, the roofing contractor cannot escape any of this. The lack of proper specification and contract document review; failure to review product data, including installation guidelines for new products; poor project oversight and management; and pressure from general contractors often result in installations that are subpar. The result is a “perfect storm” of design, materials and installation that fail under stress.
Consider the following case studies that I have been involved in as a forensic or “expert” witness when litigation was involved.
A large aged warehouse along the eastern seaboard was in need of a new roof system. Because the interior was not conditioned, thermal insulation was not required. The existing roof was an asphalt built-up with aggregate surfacing on high-density fiberboard on precast concrete panels 24-inches wide on a steel structure. The northern portion of the building had overhead doors that were seldom closed. On the interior, an aedicule structure (a building within a building) was constructed approximately 65-feet south of the overhead door, which had a ceiling level 5-feet below the roof deck.
The architect who designed the replacement roof system called for the existing BUR roof to be removed down to the precast concrete roof panels. Then a new 1/2-inch 4- by 8-foot high-density wood fiberboard was set in full-coverage spray polyurethane foam adhesive with a 60-mil EPDM membrane fully adhered to the high-density wood fiberboard.
Additionally, the architectural drawings called for rooftop relief vents to be removed and capped over.
Around June 2008, a Nor’easter (an intense rainstorm), coming in from the east off the ocean, swept into the city. This resulted in the new roof system being lifted off the roof deck. Mode of failure was the fiberboard detaching from the precast concrete roof deck.
Investigation revealed several acts and conditions that contributed to the wind damage.
PHOTOS: Hutchinson Design Group Ltd.