Source: Federal Alliance for Safe Homes (FLASH), Tallahassee, Fla.
An organization backed by Portland Cement Association, Home Depot, International Code Council and leading residential property underwriters, FLASH convened a June 6 briefing to address myths surfacing in the wake of last month’s outbreak of tornadoes in Oklahoma and Texas.
Representatives from the National Weather Service, Texas Tech University and University of Florida responded to three myths encompassing construction quality and integrity:
Myth: Nothing above ground can withstand an EF-4 or EF-5 tornado
Fact: It is entirely possible to harden and stiffen a room to withstand extreme winds, i.e. a small room, steel or concrete, or timber box equipped with a door that has been tested for pressure resistance and debris impact resistance. The National Storm Shelter Association/ICC 500 standard and FEMA guidelines provide details on how to fabricate shelters or construct safe rooms that provide near absolute life protection, even in an EF-4 or EF-5.
Expert forensic engineering examination of above-ground shelter and safe room performance during the 2011 Tuscaloosa and Joplin outbreaks as well as the May 20, 2013, Moore, Okla., tornadoes documented that properly constructed shelters and safe rooms consistently survive super tornadoes. “In my 15 years of doing storm damage research and storm shelter research, we have never documented any deaths or injuries in above ground tested safe-rooms or failures of tested safe-rooms. This includes the storms of Joplin 2011 and Moore 2013,” says Larry Tanner, Texas Tech University Department of Construction Engineering and Engineering Technology.
Myth: Building codes cannot make a difference in tornado outbreaks
Fact: Even if the tornado is EF-4 or EF-5, 95 percent of the damage occurs at EF-3 and below. What this means is that the minimal construction standards required by building codes can make a meaningful difference if they are adopted and enforced. Moreover, since 90 percent of all tornadoes never exceed EF-2, wind resistant building practices like those included in the 2012 International Residential Code can dramatically improve building performance in tornado outbreaks.
Homes built to modern, model codes will have the advantage of better wall bracing, improved roof tie-downs and overall stronger connections. “If we can put a man on the moon, we can keep a roof on a house,” said Dr. David Prevatt, assistant professor at University of Florida, Wind Department of Civil and Coastal Engineering.
Myth: We cannot affordably build to withstand tornadoes
Fact: The National Climatic Data Center estimates that 77 percent of U.S. tornadoes are in the EF-0 to EF-1 range and 95 percent have wind speeds less than EF-3 intensity. A recent cost study revealed that using an average of $0.50 per square foot or $1,000 in metal connectors installed from a wood framed home’s roof to its foundation could upgrade a home’s ability to withstand wind uplift from an EF-0 to an EF-2 tornado.
“An increase in baseline construction costs of just $.50 per square foot can boost a structure’s wind resistance from EF-0 to EF-2 levels,” said Randy Shackelford, research engineer/code specialist at Simpson Strong-Tie. A minimal investment of $.50 per square foot or $1,000 for a 2,000-sq.-ft. home will help save lives and minimize property damage.
A file of the presentation can be downloaded from www.flash.org.