Houses that defy hurricanes

Florida snowbird Mary Frances McKenzie considered herself fortunate after hurricane Charley blew through recently. Her winter home in Spring Lake, Fla., withstood the mammoth storm unscathed. The house down the block did not.

The roof on that cement-block stucco villa blew its top and crashed into her sister-in-law's back porch. "It caused a lot of water damage," says the Indiana native of her in-law's home, just two doors down.

Fortunately, many new homes in hurricane-prone areas today are built to codes to avoid such an unpleasant scenario. These include everything from domed homes that are supposed to survive 300-mile-per-hour winds to safety innovations on more conventional houses.

While progress has been made, there is still much that could be done to mitigate damage, experts say.

The winds of a major hurricane can rip apart a poorly built house, or inflate it like a balloon, says Chad Morris, associate director of the Wind Science and Engineering Research Center at Texas Tech University in Lubbock.

"That usually begins with a window or door that fails from the wind pressure," he says. "The air is then allowed to enter into the house, which lifts the roof off the home. Once that happens, it just blows the guts out of the inside. Sometimes it will blow out the back wall."

Ten years ago, the weakest link was roof sheathing and its attachment to the roof, says Tim Reinhold, of the Institute for Business and Home Safety, a nonprofit group funded by the insurance industry. "In [hurricane] Andrew, probably 90 percent of homes that had damage had some sort of roof covering damage. What we saw in Charley was that people had begun to attach roof sheathing better."

The big issue now is in the attachment of soffits, the vinyl stripping that covers the space where the roof meets the walls. This material is just being stuck in there and not being attached according to specifications, he explains. "As the wind blew in the house, the roof was staying on, but the soffit material was blowing up and allowing rain to blow right in over the wall and into the ceilings of the house," Mr. Reinhold says of his observations after Charley. "Then you get all of your insulation wet, your ceiling starts to collapse, and you've trashed your house."

Other weak links are of the human kind. Competitive pressures are pushing builders to erect homes quickly in booming coastal communities. Because of that competition, some builders will cut corners, says Ben Sill, director of the general engineering program at Clemson University in South Carolina.

Building inspectors, meanwhile, may show up in the morning to inspect roof work just starting, only to return later that day to find the asphalt shingles already up, says Mr. Sill, former director of Clemson's wind-load test facility. "Unless you have some guy standing there the whole time ... you just have to take a lot of people's word that they did it right."

The right way to install a roof, for example, includes attaching plywood with nails at six-inch intervals along the edges and eight to 12 inches up the center, says Charles Miller, an editor at Fine Homebuilding magazine and a former homebuilder. Many of the homes that sustained the most hurricane damage used staples that missed their mark, he adds. "They're not equating the results of bad building practices with the reality of what that storm is going to do with the house."

One basic safety feature that consumers should look for is hurricane strapping, flat metal strips that literally hold the trusses and rafters to the walls. Another important consideration is whether the house has shutters. And tiles need to be either screwed to the roof or embedded in a mortar patty designed to adhere to the tile, Miller says, adding that such measures don't add that much to the cost of the house.

If consumers demanded hurricane safety features, as they eventually did with car air bags, then builders would respond, Sill says. He wants a national wind-hazard mitigation program, much like a current program for earthquake hazards.

Congress is considering providing $60 million to establish a national wind-hazard mitigation program, Reinhold adds.

Is it possible to build a hurricane-proof house that doesn't look like a concrete bunker? Mark Sigler certainly thinks so.

After hurricane Ivan hammered nearby homes last week, his "dome home" on the Florida Panhandle survived the full brunt of the deadly storm with barely a scratch, Mr. Sigler says.

More than 80 percent of the houses on the barrier island were destroyed, including those on both sides of his home, says Sigler. The gracefully arched, reinforced concrete house sustained only minor damage, including to a staircase that blew away as designed to avoid damaging the structure.

The house was designed by San Francisco Bay-area architect Jonathan Zimmerman, who says the Sigler home proves that this is the strongest, safest way to build a house.

Construction of a domed home starts with a balloon inflated to the shape and size of the house. Rigid foam insulation is then sprayed on the inside surface of the inflated form, to which steel bars are attached in a crisscrossing pattern. Concrete is sprayed over the bars and insulation, with spaces left for doors, windows, and other architectural design spaces in the home.

Winds travel through the shell and wind loads are transferred down to the foundation.

Sigler's dome home weighs about 850 tons, compared to about 30 tons for a similar-sized wood house. The cost of building such a home is comparable to other designed homes, says Sigler, who adds that it's an excellent investment: "These homes are designed to last seven generations."

Sigler and his wife, Valerie, won a $245,000 grant from the Federal Emergency Management Agency to help build the house. Florida has lost an estimated $45 billion to $50 billion from the three recent hurricanes.

Since the trio of hurricanes hit in rapid succession, Mr. Zimmerman has seen a jump in the number of visits to his website, www.zdomes.com. Work is under way to build one of his dome homes in an avalanche zone in Alaska.

"We live in a crisis-reactive society," he says. "These crises have really made people change the way they think and perceive things. If anything is accomplished by this, I am hoping that people will revisit the idea of what a home needs to be and what a home needs to look like."