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These Are The Riskiest CRE Properties In A Tornado

As an F-3 tornado barreled toward a North Dallas Home Depot Sunday night, the retailer's manager sent everyone home, leaving the store empty 40 minutes before it was destroyed. 

Given the nature of that property, the level of destruction wasn't a surprise, according to research compiled by retired engineer and Texas Tech University professor Larry Tanner. 

A tornado ripping through Dallas in 1957

“If we're talking about somewhere around 140 miles an hour in [wind speed], we would expect that would have [caused] near to complete destruction of that building,” he said.

Tanner has spent three decades testing storm-resistant shelters and examining the impacts of tornadoes on residential and commercial properties. For many years, he performed this work at Texas Tech University's famed National Wind Institute. 

Now retired from Texas Tech, Tanner runs Tanner Consulting and advises commercial and public entities on how to build facilities to withstand deadly storms in Tornado Alley. He also survived the deadly F-5 tornado that struck Lubbock in 1970. 

Grocery stores and big-box retailers are among the riskiest commercial properties to seek shelter in during violent storms, Tanner told Bisnow. These types of buildings have shown consistent vulnerability during his studies.

“Tall walls and open structures can lead to vulnerability during high winds,” he said.

Tanner even studied the effects of a storm on a Home Depot that was crushed by an F-5 tornado in Joplin, Missouri, killing several people inside. The retailer was sued for its roof design, but a judge dismissed the case. 

A Dallas Home Depot crushed by an F-3 tornado in October 2019.

If people seeking shelter inside commercial buildings have a choice, smaller properties are better, according to Tanner.

“You want to try to seek refuge in a more substantial smaller building ... a grocery store or a Walmart would not be a refuge of choice because you are talking about long-span structures,” he said. 

If a person has to find shelter while driving during a storm, he recommends they look for hospitals, which usually have basements, and more substantial buildings such as banks, which are often constructed with solid architectural and design standards, he said. 

If you can see the storm and can't get into shelter, drive perpendicular to it to get away, Tanner said. 

A damaged fire station in North Dallas after an F-3 tornado touched down in October 2019.

Building F-5-resistant commercial buildings is highly doable today and affordable depending on how a company views the costs and benefits, Tanner said. 

He has personally tested tornado-resistant windows and doors that can withstand F-5-level winds. 

“You are talking about 5 SF per occupant [in a shelter], so if it's just a little retail space, you can probably get by with a $7K to an $8K or $10K shelter that you just sit on a slab in that retail space. You can also do that in an apartment house. It’s doable. It's affordable, and it will save lives.”

A small safe room for a house can run as low as $3K to $4K, Tanner said. 

Schools appear highly intrigued by the possibility of installing tornado-resistant safe rooms. Tanner has advised schools in different parts of Texas on how to place storm shelters inside their buildings. 

Today, the U.S. has the technology to drop storm-safe rooms into existing buildings, connecting them to concrete slabs. Architects can also design safe spaces in new schools where an entire room is made up of some type of reinforced concrete and steel, and the windows are F-5-storm resistant, Tanner said. 

With mass shootings also an issue, Tanner said by adding a bit more reinforcement to the safe rooms' doorways, schools and commercial landlords also can create areas that double as panic rooms to escape active shooters. 

Tanner said he sees more people using the technology, and he knows a number of large commercial companies putting pre-manufactured safe rooms into their office towers.

“It’s very doable,” he said. “It costs more per square foot than your normal building will, but it kind of depends on where your value is. I would rather spend money to protect our children in the school as opposed to putting new AstroTurf on our football field."