Cyclone-proof Roofs

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Cyclone-proof Roofs

This house was left roofless (and missing some walls) after a tornado touched down in Kentucky.

Hemera/Thinkstock

During a powerful storm, one of the biggest risks is having the roof ripped off your house. The powerful winds blowing over your home will exert inward pressure against the far wall that's downwind, push outward against the opposite wall and the side walls, and push the roof upward. If your roof beams aren't strongly connected, the roof will lift off, leaving your house's walls without any lateral stability or bracing. That, in turn, will cause them to collapse outward, so your house will appear to explode [source: DeMatto].

This happens a lot, particularly when tornadoes strike. Outside of hurricane zones, most building codes only call for roof trusses to be connected to the top of exterior walls with 3.5 inch (9 centimeter) nails. Those connections are enough to withstand brief gusts of wind at speeds of up to 90 miles (145 kilometers) an hour. But even an EF1 tornado (the smallest class of twister) is going to have much more powerful wind [source: Hadhazy].

In the future, you may be able to buy a house built from super-strong carbon fiber or from Kevlar, the material used in bulletproof vests, which could survive such forces unscathed [source: Fox]. But in the meantime,

you can install galvanized-steel "hurricane clips," which brace portions of the trusses or rafters in a house. These strengthen the roof so it can withstand battering by 110-mile-an-hour (177 kilometer-an-hour) winds. A 2,500-square-foot, two story house can be equipped with clips for around $550, including labor [source: DeMatto].

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