Basements are the safest place to be during a tornado but they weren't built for that
Basements are very much a function of the region of the US where the house is built.
FOX Weather Explains: Tornado Safety
FOX Weather meteorologists Britta Merwin and Jason Frazer explain why tornado safety is so important.
When tornado sirens are blaring, wondering where to seek shelter from the storm is the last thing you want to be thinking.
And while your home's basement is the safest place to be in a tornado, they weren't built as storm shelters.
While a basement may provide some protection against weaker tornadoes, houses – and most buildings in general – aren’t designed to resist the most extreme wind speeds associated with tornadoes like the ones that struck Illinois and Kentucky in late 2021, according to Rose Quint, the assistant vice president of survey research at the National Association of Home Builders.
"Only a storm shelter or safe room specifically designed to resist tornadoes will keep occupants safe," Quint said. "A portion of a basement could be constructed to those standards if a homeowner desired, or prefabricated units that can be bolted to the concrete floor of a basement are available."
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New homes in the South lack basements
Most basements are reinforced concrete walls buried underground. The International Residential Code, which forms the basis for most residential building codes adopted in the U.S., tabulates how thick a concrete or masonry basement wall needs to be and the amount of any steel reinforcing needed in the wall. The code also specifies measures to protect against groundwater or rainwater leaking into a basement.
"The digging has to happen by code," Quint said.
That code, she added, requires the footings of a house must extend at least 12 inches below the undisturbed ground surface or to the frost line – the depth to which the ground freezes in the winter. For some regions where it’s already necessary to dig deep to build foundations that will withstand freezing temperatures, adding a basement makes economic sense.
"The frost line is much deeper in the colder Northeast and Midwest regions of the U.S. than in the warmer South and West, as much as 3 or 4 feet below the ground in some places," Quint said. "Once you are excavating down that far and removing that much soil, going down a few more feet to create a basement is cost-effective."
When comparing new homes in the U.S. and across the four regions, the United States Census Bureau showed the share with a full or partial basement in 2020 was as high as 68% in the Northeast and as low as 6% in the South, where the ground is not conducive for basements.
"In Florida, the high level of the water table makes it impossible to have a basement," Quint said.
No such thing as guaranteed safety when it comes to tornadoes
But recently, the South has been among the most active for tornadoes.
There were 1,374 tornadoes in the U.S. in 2021, and about 10% of them were reported in Texas. Alabama and Mississippi were a close second and third with more than 200 combined.
(FOX Weather)
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There is no such thing as guaranteed safety inside a tornado, according to the National Oceanic and Atmospheric Administration's Storm Prediction Center.
But while the most violent and rare EF-5 tornado can level and blow away almost any house, most tornadoes are much weaker and can be survived using some safety precautions – chiefly, taking advantage of a basement if your home happens to have one.
In a house with a basement, NOAA recommends avoiding windows and finding a sturdy object to hide underneath, like a heavy table, or cover yourself with a mattress or sleeping bag.
"This protects you from flying debris and also walls or roofs that may collapse," says FOX Weather meteorologist Stephen McCloud. "There have been several studies on where to go or what corner of the basement do you shelter in. Regardless, being underground is your safest bet."
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You also want to avoid staying under any heavy objects that might be placed on the floor above you, like a refrigerator or furniture. A weakened floor might cause those items to crush you.
If you don't have a basement, an interior room of your home with no windows is the next place to go in the event of a tornado.
Anyone living in a mobile home should get out and find a more stable structure where they can take shelter.