Stronger construction standards can reduce tornado destruction

Oklahoma City — “The devastation and damage to homes and businesses caused by tornadoes can and should be reduced by better construction methods,” said Tim Reinhold, Ph.D., chief engineer and senior vice president of research, Insurance Institute for Business & Home Safety (IBHS). Reinhold presented several new recommendations to reduce tornado damage through stronger construction practices during his presentation at the National Tornado Summit in Oklahoma City. He went so far as to call on home buyers to demand safer homes in tornado-prone areas, especially manufactured homes.

Reinhold shared work he is doing with the Applied Technology Council (ATC) to produce a construction guide for tornado-prone areas. He also noted the importance of including internal pressures in design of buildings in tornado-prone area and discussed the logic behind new proposals under consideration by the American Society of Civil Engineers (ASCE-7) Standards Committee.

In addition, Reinhold discussed the importance of creating a continuous load path to reduce tornado damage (Learn more about creating a continuous load path in IBHS’ animation video.) “We can more than double the strength of buildings to resist wind loads by installing the connections correctly,” Reinhold said. “While IBHS focuses on strengthening homes and business so they can stand up to Mother Nature during most tornadoes and other catastrophic events, these storms don’t just destroy buildings, they devastate families and communities, and that’s really where our concern lies. There is no such thing as a tornado-proof home, but builders can definitely make design improvements to narrow the swath of property damage.

“For example, IBHS believes the damage caused to manufactured homes by EF0, EF1 and most EF2 tornado winds can be greatly reduced if buyers select manufactured homes built to U.S. Department of Housing & Urban Development (HUD) Code Zone III Exposure D (open water exposure wind design) standards and have them installed on permanent foundations,” Reinhold said. “Manufactured housing that is built to these standards and installed on permanent foundations will actually be considerably stronger than most conventional wood frame housing built in the middle of the country.”

He further noted that “HUD Code Zone III standards meet the requirements of the stronger building code ordinance adopted by the Moore City Council following the devastating EF-5 tornado that struck the city in 2013. According to HUD’s standards for manufactured homes, the majority of the country is in Zone I, with only a narrow sliver of the Gulf and Atlantic Coasts in Zone II, and the southern-most portions of Louisiana and Florida in Zone III.  There are more than 8 million manufactured homes in the United States, and consumers seeking to purchase new ones should demand the strongest and safest construction possible, which is a HUD Code Zone III home.”

Reinhold has evaluated the wind performance of manufactured housing in the field and in laboratory testing at IBHS’ Research Center. Following Hurricane Charley in Florida in 2004, IBHS joined a post-disaster assessment team in studying building damage. As part of the study that focused on building codes and the performance of manufactured homes, they found that HUD Code Zone III homes performed uniformly better than older, lower wind-rated manufactured homes.

IBHS also conducted laboratory wind performance testing on manufactured homes last year. The research confirmed that HUD Code Zone III manufactured homes can withstand wind loads up to and beyond their wind design capacity, even when the windows and doors were opened on the windward side to simulate the effects of debris damaging the openings, as seen in tornadoes and hurricanes.

Download IBHS’ Consumer Safety Guide for attached structures based on its manufactured home testing at https://www.disastersafety.org/studies-reports/consumer-safety-guide-carports-attached-structures.  

Additional resources are available on IBHS’ Tornado Resources webpage at www.disastersafety.org/tornado.