The Creation of the First Tornado-Resistant Building Codes

Tornadoes pose a significant threat to life and property due to their devastating power – they are responsible for claiming more lives annually in the U.S. than hurricanes and earthquakes combined. According to the National Oceanic and Atmospheric Administration (NOAA), the U.S. experiences an average of over 1,200 tornadoes each year, with about 60 of them reaching an intensity of EF-3 or higher on the Enhanced Fujita scale.

It is essential to take proactive measures for disaster prevention, including ensuring that buildings are constructed and maintained according to modern building codes and standards like the International Codes®. Such measures can greatly enhance the structural integrity of buildings, increasing their resilience against the destructive forces of tornadoes and ultimately saving lives.

Tornado-Resistant Building Design and Construction

For years, U.S. building codes lacked the inclusion of tornado-resistant design and construction requirements, resulting in an increase of property damage and loss of lives during such disastrous events. Thanks to the dedication of Long Phan and Marc Levitan, structural engineers at the National Institute of Standards and Technology (NIST), this has changed.

Phan and Levitan led a decade-long effort to create the world’s first tornado design standards which enable builders to construct buildings to withstand 97 percent of the tornadoes that occur in the U.S. each year.

Before their work, builders and engineers considered tornadoes as uncontrollable acts of nature – too severe, unpredictable and costly to incorporate into building design plans. This belief stemmed from the limitations of the original Fujita Scale, which until 2007 often exaggerated tornado wind speeds by disregarding factors like building quality and design when assessing damage.

In 2011, Phan and Levitan investigated a powerful EF5 tornado in Joplin, Missouri, and made a fascinating observation during their study: despite the tornado’s widespread destruction, a hospital complex managed to keep an entire floor intact because of its impact-resistant exterior. This finding suggested that it might be possible to design buildings to withstand tornadoes. As a result, Phan and Levitan recommended that NIST create national standards to guide building safety efforts.

“They translated important research into practical engineering terms that the average practitioner could use to design and build safer buildings,” said Dominic Sims, CEO of the International Code Council.

After an extensive consensus process, the American Society of Civil Engineers (ASCE) approved the new tornado wind load standard created through Phan and Levitan’s research in 2021. Additionally, a committee tasked with revising the International Building Code® unanimously adopted the new regulation for implementation in 2024. 

To learn more about the creation of the first tornado-resistant building codes, click here.  

For International Code Council resources on disaster preparedness, click here.