Jeff Masters Weather Blog

How to make your home more tornado-resilient » Yale Climate Connections

Portrait photo of a woman smilingPortrait photo of a woman smiling

The essay below was written by Daphne LaDue, a senior research scientist at the University of Oklahoma’s Center for Analysis and Prediction of Storms. LaDue focuses much of her research on how emergency managers make and adapt their severe weather preparation decisions based on forecast briefings and uncertainty, past experiences, and the unique characteristics and vulnerabilities in their jurisdiction. LaDue is also collaborating with wind and structural engineers to explore how tornado survivors’ observations might inform conclusions on how tornado damage unfolds. Their data include information on forecast and warning messages received, when and how survivors made decisions, and how effective any sheltering decisions were.

I can still remember the queasy feeling I got in my stomach as I read FEMA’s Building Performance Assessment Team report on the May 3, 1999, tornadoes in central Oklahoma. The team of scientists and engineers had determined how winds in and around the tornadoes had interacted with dozens of homes, including from inflow winds well away from the tornado itself. It was fascinating, and troubling: By the end of the report, I could vividly imagine how my home would come apart during a tornado.

Since that time, engineers have studied thousands of homes damaged by tornadoes, other types of windstorms, and hurricanes. And the Insurance Institute for Building and Home Safety has tested strategies for fortifying homes in their full-size wind tunnel and shown that simple improvements can make a huge difference.

A map of the area surrounding Moore, Oklahoma.A map of the area surrounding Moore, Oklahoma.
Figure 1. As of this writing, the most recent U.S. tornado rated F5 or EF5 was the one that struck Moore, Oklahoma, on May 20, 2013, taking 24 lives and causing an estimated $2 billion in damage (USD 2013). Adjusted for inflation, this was the nation’s third-costliest tornado on record. However, only a small fraction of the path (bright red, in center of path) experienced EF5 damage. Many of the tornado-struck areas experienced no more than EF1- or EF2-level damage (teal and light green, respectively). (Image credit: National Weather Service/Norman OK)

Given that over 95% of all tornadoes do EF2 damage at their worst, and that 90% of the area in the very strongest tornadoes is EF3 or below, there are simple changes that would make a huge difference. Some estimates put the cost per home at only $1.50-$2 per square foot for new construction. The anchors and metal clipping connecting all of the wood framing from ground to roof are inexpensive. For those of us with existing homes, anchors and clips can be added any time a room is renovated down to the studs.

Photo of a damaged house.Photo of a damaged house.
Figure 2. Homes like this one sustained damage but protected the occupants. This was on the fringe of a tornado path in an area of less damage overall. (Image courtesy Daphne LaDue.)

I was fortunate in recent years to have teamed up with structural engineer David Roueche (Auburn University) and wind engineer Frank Lombardo (University of Illinois Urbana-Champaign) in a project we called Survivor Stories. Our first deployment was to the aftermath of the Beauregard tornado in Lee County, Alabama, in March 2019. Although I had been in tornado damage areas on several occasions, and even helped the National Weather Service with several damage surveys, it was in this tornado that I saw my first “slider.” The home had lost its roof but otherwise stayed intact as it slid off its foundation and along the ground for around 80 feet! This home was a “stick-built” home, meaning it was made of wood framing. It turned out that several homes in the area were essentially sitting on their foundations with no attachments like this one had been, but when the others came off their foundations, they fell apart and injured or, in one case, killed the occupant.

Photo of a structural issue where a wall meets the ceilingPhoto of a structural issue where a wall meets the ceiling
Figure 3. This home illustrates an anchoring issue that is surprisingly common in the southeast United States. Note the j-bolt from the sill plate installed in the mortar-filled head joint of a concrete masonry block (top center, encircled in yellow). Note that the concrete blocks are not reinforced, and the wall is severely cracked. (image credit: Courtesy Daphne LaDue.)

In that tornado, the vast majority of fatalities were people who were in a mobile or manufactured home when the tornado struck. Some of these homes were strapped to ground augers, but many were not anchored at all and readily rolled right off their foundations.

Any time a home is heavily damaged, it is devastating to the occupants and their precious family possessions. One of the survivors we spoke with bemoaned losing all the family portraits he had on one of his walls. He was doubtful he would ever see any of those photos again.

We know how to build better. We just need to start doing that. And for those homes that already exist, any time you do some repair or renovation that exposes the framing, you have an opportunity to strengthen the framing connections to resist uplift forces. Contractors need to know about this — and need to believe it will work — as do consumers, who can then demand these changes. If you live in an area with no housing regulation or are a do-it-yourselfer, you can do this yourself through resources such as this educational site from one manufacturer of the connectors you would need.

Photo of a damaged home that has less damage than surrounding ones.Photo of a damaged home that has less damage than surrounding ones.
Figure 4. This home sustained less damage than expected given its location in a tornado path. Talking with the homeowner, the research team learned he had built above code, adding hurricane clips to his roof. While those alone do not complete a continuous load path to the ground, they help resist damage. (Image credit: Courtesy Daphne LaDue)

Interrupted lives

My role in the Survivor Stories project was to talk with the people we encountered in the tornado damage zones, those who had firsthand experience with a tornado. I am forever grateful to those who shared their experiences with us. By the end of the project, we had spoken with over 100 people in several states.

While there isn’t room here to fully characterize all that we heard, I want to stress one important truth: Storms can truly surprise people, even when they knew tornadoes were in the forecast. They reminded me of something I knew, but I had overlooked: From the perspective of an individual, a forecast does not mean a tornado. Neither does a warning. Even when there is a tornado in the area. Did it hit you? Probably not.

In interviews ranging from eight minutes to over an hour, we learned a lot about how tornadoes interrupt people’s lives:

  • In Lee County, Alabama, the tornado struck during the early afternoon on a Sunday in early March. People were listening to music, napping in front of a Western on TV, or watching a favorite Oscar-winning movie.
  • In Cookeville, Tennessee, the tornado struck after midnight in early March. Many were sleeping, but some were still up or woken up by either health issues or the sounds of the approaching storm.
  • In Mayfield, Kentucky, the tornado struck near dinnertime on a Friday in mid-December and had been on the ground since Arkansas. People were just home from church; just off work, which had closed early because of the storm; or at home engaged in their usual Friday evening activities, if not distracted by the news they were hearing about a long-track tornado headed their way.
  • In Arabi, Louisiana, the tornado struck on a Tuesday evening. Schools and some employers had let out early. People were putting children to bed, eating dinner, or watching TV.
Photo of a child's bedroom with the roof and ceiling ripped offPhoto of a child's bedroom with the roof and ceiling ripped off
Figure 5. A child’s bedroom is open to the sky after a tornado pulled the roof off of this home. (Image credit: Daphne LaDue)

These stories illustrate a range of experiences found across the interviews. Whether people knew about the chance of tornadoes or not, and whether they had a tendency to believe the forecasts and warnings or not, phone notifications were crucial, as was live TV coverage, friends and family who heard about the storms and called, and environmental cues from the storm itself. Most of these occurred with very little lead time before the tornado struck.

These folks all live in parts of the country where they have a chance of tornadoes several days every year. It’s not reasonable to expect people to interrupt their lives for hours for every forecast, some of which would occur overnight — which emphasizes the importance of having adequate shelter right where you are. An engineered storm shelter inside or outside of your home is helpful, but these stories also illustrate the benefit of simply building stronger.

Even here in central Oklahoma, in the heart of Tornado Alley, the odds of my home being struck are something like 1 in 1,000-1,400 each year. But I would like my home and the ones around it to be more resilient, giving me more peace of mind that my home will protect me well enough for me to survive — and even retain many of my belongings.

In fact, a dream of mine is that engineers and the National Weather Service will start to have a difficult time rating tornadoes … because so many homes have been strengthened to be more resilient against windstorms.

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