Built for stormy weather
Product developers at Simpson Strong-Tie pay attention to hurricane damage.
Randy Shackelford has been tracking hurricanes for years — not as a meteorologist or storm hunter, but as manager of codes and standards for Simpson Strong-Tie, creator of structural products for buildings and homes.
Much like a representative of the National Transportation Safety Board (NTSB) will investigate the scene
of a civil transportation accident, Shackelford will visit an area following a hurricane in hopes of gathering useful information for future product development. To him, names like Hugo, Andrew and Katrina are synonymous with landmark hurricanes that yielded meaningful changes in the building materials industry.
“We learn something from every hurricane,” he told HBSDealer. “There was a big change in 1989 with Hurricane Hugo [which struck the Southeastern U.S.]. Before that there was a hodgepodge of code and code enforcements and houses weren’t given that much attention, but after Hugo we learned there were houses designed that went undamaged while next door there were homes that were heavily damaged. We went out to find out why. When we pay attention to these things, we learn that we get great results.”
In 1992, for example, Hurricane Andrew’s lesson was that building codes in South Florida’s Dade County needed upgrading, specifically requiring impact windows, stronger ties between roofs and walls, and securing roof shingles with nails instead of staples. In Florida, roof straps that connect a home’s roof to the foundation became mandatory in areas where 120 mph winds can be expected. In coastal areas, Shackelford said new structures are required to have a “continuous load path” that directs wind loads on the roof and walls down to the foundation. Continuous load path is a method of construction that uses a system of wood, metal connectors, fasteners (like nails and screws) and shear walls to hold the structural frame of the house in one piece. A continuous load path is critical during a storm because it helps hold the house together when high winds try to pull it apart, according to Shackelford.
This has led to widespread use of tie-down straps, J-bolts, cable ties, expansion bolts, hurricane clips and plates. Other proven ideas to prevent wind damage include strengthening gable ends, limiting roof overhangs, using glue and ring shank nails on roof sheathing, taping sheathing seams, and extending fascia boards below the soffit of overhangs.
Shackelford said there is a new trend toward “code-plus” programs and a focus on resiliency with regard to hurricane-resistant building. “Over the last 10 years or so code-plus programs have evolved, particularly the IBHS Fortified program (disastersafety.org/ fortified). This program has specific levels of improvements that can be made in steps (Bronze, Silver, Gold) to build a home with better storm protection than the code minimum. The concept of resilience is also becoming important.”
A group from within the building industry has defined resilience as “the ability to prepare and plan for, absorb, recover from, and more successfully adapt to adverse events.” This is the concept that communities should be able to not just survive storms, but recover quickly, so that the community can go back to normal quicker.
Michael Rimoldi, senior vice president of education and technical programs at the Federal Alliance for Safe Homes (FLASH), advises FEMA on building hurricane-resistant homes. As he explained, “in the traditional wood- frame home, it’s how it’s all put together. All of the components, from the top of the roof down to the foundation, are tied together by mechanical connectors. You can build a wood-frame home that’s just as strong as anything else as long as you ensure that all the walls are tied together properly, are tied to the roof properly, and the roof and walls are tied to the foundation properly.”
A more recent innovation in tie-down products is a new truss screw featuring fully-threaded shanks for fastening trusses and rafters to top plates as an alternative to hurricane clips. The screw is used for stud-to-bottom plate connections as well. Simpson’s Strong- Drive SDWC Truss screw, for example, can handle up to 600 pounds of uplift. “Contractors love them,” Shackelford said, noting that all the connections can be done from inside of the structure.
Other heavy-duty connector screws, such as the Simpson Strong- Tie Strong-Drive SDS, is a 1⁄4-inch -diameter high-strength structural screw ideal for various connector installations as well as wood-to-wood and engineered wood applications. It installs with no predrilling and has been extensively tested in various applications, including hurricanes. “Every year we learn more,”
Shackelford added. “We see the wind loads go up as the houses [near the coast] get bigger, therefore we come up with a new product with greater uplift. We are constantly testing new products. We like to think of ourselves as an innovative company that helps make structures safer and stronger.”
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