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Property owners can fortify their homes and build or buy special shelters to better withstand the forces of tornadoes -- and that's not a bad idea if you live in tornado-prone regions, given the recent tornado devastation.

The more than 400 tornadoes that struck primarily in the central U.S. during the first 10 days of May were the most in a short period since the National Oceanic and Atmospheric Administration began tracking them in 1950.

The insurance industry says the twisters could add up to its most costly event ever -- more $2.2 billion in insured losses. More than 300 counties affecting 19 states suffered losses and more than 40 deaths were blamed on the storms, according to Boston-based AIR Worldwide, which uses computer modeling to estimate insured catastrophic losses.

While you can't build a tornado-proof home, you can come close, depending upon the tornado and the structure.

For the sake of comparison, hurricane gales range from 74 miles per hour to greater than 155 miles per hour. At the lower end, unanchored mobile homes are in danger. At the higher end roofs blow and some buildings fail and are destroyed, according to The Saffir-Simpson Hurricane Scale.

The more concentrated, swirling winds of a tornado range from 40 miles per hour to 318 miles per hour -- or more. At the low end, tree twigs snap, chimneys crumble and windows break. At top tornado speeds, destruction is phenomenal: strong frame houses are lifted off foundations, carried considerable distance and then disintegrated, auto-sized missiles fly at speeds nearing 300 miles per hour and trees are debarked, according to the Fujita Tornado Intensity Scale.

The Institute for Business and Home Safety, which offers "Protect Your Home Against Tornado Damage," says homes typically are constructed to withstand speeds up to only about 70 miles per hour with weaker parts prone to damage at slower wind speeds.

Good construction choices, however, can take some of the headache out of wind worry.

The institute, which offers information on building a new home that's fortified against wind storms and related costs, also recommends improvements designed to keep the wind out of your home. Once inside, the wind creates a double threat of force on both sides of your home.

  • "Impact-resistant" window systems help give your home a better chance of surviving wind storms. Use impact-resistant laminated glazing materials for sliding glass doors as well.
  • Well-anchored and dead-bolted entry doors in strengthened door frames likewise let the wind knock, but not come in. Garage doors more than eight feet wide are especially susceptible to wind forces. They can be constructed or retrofitted with stiffeners and stronger tracking systems to resist higher winds.
  • Roof systems are available to withstand high winds and include well-sealed sheathing (to prevent wind and moisture intrusion) and braced gables to prevent winds from lifting roof ends. It's also important to firmly anchor the points where the roof and the foundation meet the walls of your house. For two story homes, the upper story should likewise be firmly anchored to the lower framing.

    Safest room in the house

    Even with the most professional construction or retrofit work you could still lose much of your home in the worst tornado, but if you've prepared a sturdy "safe room," chances are, you and your family will survive unscathed.

    When constructed according to Federal Emergency Management Agency plans, so-called safe rooms provide protection from winds of up to 250 miles per hour and against 100 mile-per-hour projectiles.

    Researchers, emergency response teams, and others on the scene up after a tornado often find an interior room of a house still standing when the rest of the home above ground has been destroyed.

    That means closets, bathrooms, and small storage rooms are ideal retrofitting candidates. Not only are they often centrally located, they retain an ongoing function other than merely providing occasional storm protection. Also, such rooms typically have only one door and no windows. Bathrooms have the added advantage of a water supply and toilet.

    Tornado safe room plans generally call for small, five-square-feet-per-person reinforced wood-frame, concrete or masonry rooms. For protection from hurricanes, which last longer than tornadoes, you may consider the comfort of the occupants and double the square footage per person.

    FEMA's plans are based on a maximum 64 square feet of space with a maximum wall length of 8 feet for any single wall. For hurricane protection, a shelter of that size can accommodate up to six people in reasonable comfort.

    Safe rooms cost approximately $3,000 to $6,000 in a new home and 20 percent more ($3,600 to $7,200) to retrofit an existing home, but the U.S. Department of Housing and Urban Development's special Federal Housing Administration-insured loans can loan you up to $5,000 in added-on financing to cover the cost of building a wind shelter.

    Bunker down

    Another option, currently marketed as a terrorist turnoff, is a $48,000 bunker that has the U.S. military's attention.

    "Your home can physically fall on top of the unit and there would be no more problems than a scratch on the paint," boasts designer Jorge Villa, a University of Miami mechanical engineering graduate with majors in civil and industrial engineering.

    That should just about take care of the largest tornado wind-borne projectile.

    Villa's Homestead, FL-based U.S. Bunkers offers a diamond shaped 13- to 18-ton, water tight, fireproof, rustproof, bulletproof shelter, the Multi Purpose Platform Bunker (MPPB), made of 1/4- to 3/4-inch rebar reinforced concrete, steel, a super mix of polymer fibers and a "boat-like" Fiberglas interior.

    An above-ground Guardian model, starting at a cool $34,500, looks like a buff moon lander with hefty steel supports. At a foot thick, seamless and windowless, the bunkers can be tripped out with host of features including an air ventilation system, biochemical filters, heat/air conditioning, video surveillance with a monitor/TV and VHS recorder/player, 12 and 120 volt lights and outlets, cable, phone and Internet hookups, battery-backed solar panels, water and fuel tanks, refrigerator, portable potty, first aid kit, an electric entryway and escape hatch. Power packs can run the ventilation system for 12 hours or more after a power failure. Add benches, beds, desks and shelving and it's home sweet survival home.

    With an interior diameter of 9 feet, a height of 6 feet 4 inches, the shelters offer 76 square feet of living space designed to hold six adults and when you aren't cowering from a storm, the bunker can double as a playhouse, sauna-steam room, temporary guest quarters or a hide-out in the not so brave, new security-conscious world.

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