How to make your home more tornado-resistant
If an extremely powerful tornado drops down on a home, there's not a lot you can do. But you can strengthen your home to make it more resistant to high winds.
© Eric Nguyen/Corbis
Tornadoes this year have ravaged several U.S. states, including Alabama, Georgia, Indiana, Kentucky and Ohio. The severe storms have killed dozens of people and injured hundreds more. The stories are incredible: In one horrific incident, the legs of a 36-year-old Indiana woman were severed by collapsing steel beams as she huddled in her basement with her two children. She survived, and her children, whom she had wrapped in a heavy blanket, escaped serious injury.
This dramatic example raises a fundamental question that is surprisingly difficult to answer: Can a home be built to withstand a tornado?
The answer is yes — if the home were constructed like a bomb-proof bunker, with thick walls, a reinforced concrete roof and a superstrong internal support system to prevent structural collapse. Window and door openings would require fortification with impact-resistant shutters that could be swung shut and locked at a moment's notice.
None of this is practical for the average home, which is built out of ordinary construction lumber, plywood and particleboard. Even a well-built house with walls of brick or stone is vulnerable to a tornado. But wood-frame structures are particularly at risk: Siding and roofing blow off or are pulled away by suction; subassemblies of rafters and wall studs with plywood attached are peeled away; sheets of plywood turn into sails, multiplying the already intense force of the wind; long pieces of lumber exert tremendous leverage.
In short, a tornado turns a wood-frame house into a gigantic, wind-driven pry bar. Once the departing structural elements have left a hole in the structure, the wind enters and dismantles the home like a bomb.
- On our blog, 'Listed': A tornado destroys a house in 4 seconds
Given this awesome power, the question is not how to "tornado-proof" a house, but rather how to increase its resistance to damage. That much is possible, according to the engineers we contacted, such as Randy Shackelford, a licensed structural engineer with Simpson Strong-Tie, a company that makes high-strength metal connectors.
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"Studies of tornadoes (that occurred in 2011) revealed weaknesses in the load path of homes built to the minimum standards of the International Residential Code, which is the most widely used building code in the United States," Shackelford says. "To resist high winds, whether they're from tornadoes or hurricanes, homes must be built with what is called a 'continuous load path,' a series of reinforced connections that tie every element together from roof to foundation, like a chain. Important connections would include rafters to top plates, top plates to studs, studs to bottom plates and bottom plates to foundation."
But in fact, Shackelford says, stronger construction really isn't sufficient. "For the ultimate safety from the strongest tornadoes, homeowners should consider a safe room," he says. "These are built to resist the highest winds that are anticipated. They provide life safety in the strongest storms."
The importance of load path
The key thing to understand is that a house is prone to its parts being ripped off and pried apart. The nails that fasten the parts end up becoming nothing more than flimsy hinges. To make the home's parts perform like a monolithic structure — and resist those massive prying forces — you have to either build it so it performs like a single piece or you have to retrofit it. That's creating the "continuous load path" to which Shackelford refers.
You do this with steel connectors that bridge the house's framing components — rafters to top plate, for example. Each connector is made from a thick piece of steel and fastened with multiple nails, screws or even bolts. In the event of damaging high winds, the home's parts are not easily torn loose because the forces are not concentrated but distributed from one wood framing member to another by means of the steel connectors and their nails, screws and bolts.
I don't mean to suggest that retrofitting a house for high-wind resistance is easy. It's not. Building materials, insulation, plumbing and wiring block access to the framing. And other components can be extremely vulnerable. If your garage door blows in, all the work put into fortifying the structure won't do much good. Fortunately, there are vertical door braces that can be installed after the house is built, which we covered during last year's tornado season.
Once the individual members of a home's framing have been fastened together, either in a massive retrofit remodeling job or in new construction, you still can't treat a tornado as a casual event. When sheltering at home, your best bet is to follow these guidelines set by the Federal Emergency Management Agency.
I own a brick home which will still not avoid damage if a tornado make a direct hit. Last year,two tornadoes hit our small town on the same night. One touched down only two blocks from our home. If it had touched down just a few seconds earlier, it would have been a direct hit on our street. My family and I (including two dogs and a cat) heard it go over while we were munching on chips,drinking sodas, and listening to the radio while sitting safely in the underground concrete storm shelter located a few steps from the back door.
Anyone who lives in an area prone to tornadoes is foolish NOT to have a storm shelter. What price can you put on your life and the life of your family ? Everything else is replaceable.
Build a Dome! Rectangular or square shapes with sharp edges don't workwell in Tornadoes but unfortunatley that's what banks like!
The only way to make your house tornado resistance is to bury it like a storm shelter, or build a "Berm" type structure... 99.9 percent of homes built in tornado alley are flimsy and will never stand up to a hurricane or tornado.
I live in the Oklahoma panhandle and know an older gentleman in one of the towns here that lives in a converted quonset hut that he has reinforced with cinderblock walls that are filled with concrete and a roof that is attached with huge tractor or construction machinery springs to allow the roof to lift off the house a certain amount when pressure is created inside the house by winds and then to subsequently sit back down in place once internal pressure is released not to mention reinforced windows and doors throughout. He was an engineer and tinkerer of sorts.