Do garage doors open the door to tornado damage?

The garage door is often the first thing to go.

When high winds, especially tornado winds, hit a typical suburban house, the failure of many garage doors to withstand the force can become the first link in a disastrous chain reaction. Minnesota has moved in recent years to require somewhat stronger construction standards for doors, but communities elsewhere have gone further.

Some question whether stronger garage doors are worth the additional cost, since no door can stand up to the full fury of nature.

Last year, the state Department of Labor and Industry required that newly constructed residential garage doors must be able to withstand a 90-mile-per-hour gust for three seconds. The old standard had been 80 mph.

Although the move put Minnesota in line with most noncoastal states, it hardly mandates garage doors be built to stand up to the reality of tornadoes. In Rogers two years ago, a tornado clocked 157 mph. In May's twister in Hugo, winds may have reached 167 mph.

Loren Kohnen, city building inspector in Rogers, saw the problem firsthand. In too many instances, Kohnen said, damage from the September 2006 tornado began when a garage door simply blew off, allowing in a rush of wind that sometimes blew the garage itself into the next house.

"Turned out to be the garage doors were the biggest problem of all," Kohnen said. He bluntly told state officials that "you guys got to do something" about requiring stronger residential garage doors.

The state's response seems inadequate to some.

"They kicked [the standard] up 10 miles per hour, literally," said Peter Kulczyk, a former Minnesota building code official now working for Washington-based International Code Council. That change, he said, is "not significant."

There seems to be little appetite for doing more.

Garage door standards are based on typical wind patterns for particular parts of the country, and tornadoes are seen as atypical events. Additionally, reinforcing existing garage doors or buying stronger ones means spending more money.

What most states use

After the May 25 tornado in Hugo, the Department of Labor and Industry said it received inquiries about the garage door requirements. Last month, it issued an advisory reminding builders and homeowners of the new 90-mph standard.

But James Honerman, an agency spokesman, said there were no proposals in Minnesota to go beyond what most other states use.

Although cities cannot legally force builders to exceed the state code, homeowners who "want to spend the extra money for that reason" can work with their builder, said Honerman.

Honerman advises that homeowners wondering about the strength of their garage doors should contact the doors' supplier or manufacturer, or identify the door's model number and seek more information online.

Nothing would withstand it

Since at least the early 1990s, the Federal Emergency Management Agency has looked closely at the damage caused by garage doors, particularly during hurricanes but also during tornadoes. After tornadoes struck Oklahoma and Kansas in May 1999, then-FEMA director James Lee Witt announced recommendations that included having "an inspector look at your garage door -- especially if it is a double-wide door. Bring it up to or exceed the code."

At Clopay Building Products, an Ohio-based company that bills itself as the country's largest residential garage door manufacturer, Mark Westerfield said making a garage door strong enough to withstand storm-generated winds is difficult.

He said that some Clopay garage doors sold in Florida are tested by firing a 9-foot-long 2-by-4 from an air cannon; the 2-by-4 is fired at the weakest point at 50 feet per second. "This test is a tough one to pass on a garage door, but it can be done," he said.

Westerfield, the company's manager of product development and engineering, said another test done specifically for tornado-like winds involves launching a 12-foot-long 2-by-4 at 80 feet per second, or about 54 mph. "The few times I've seen this test performed," he said, "the 2-by-4 went through a concrete block wall."

A Clopay garage door that meets the 90-mph rating, he said, can cost as much as 17 percent more than a traditional door, depending on the model and size.

Minnesota's new requirements for garage doors were adopted from language in the International Residential Code, which is updated every three years.

Jennifer Gibson of the International Code Council, which produces the residential code, echoed many others when it comes to garage doors -- and even houses: "You can build the strongest structure in the world and there's going to be a tornado that can take it away," she said.

Although there were unofficial reports that garage doors created much damage in Hugo's tornado, there has been no specific study to pinpoint their role.

Kevin Corbid, the Washington County official who recently released a damage report on the storm, said there was at best only anecdotal evidence of the damage that garage doors caused. Corbid's report said 39 houses were destroyed by the tornado, 302 were damaged and the total damage was $22.3 million.

"We certainly could see that there were times when a garage door was bowed out or bowed in or was missing," he said. "We wouldn't have looked further to see if that caused other damage."

Michael Ericson, Hugo's city administrator, said "some people were theorizing" initially about the role played by a house's design and garage door. But with 165-mph winds, he said, "there's no way anything's going to withstand it, so that was the end of the story."

Double the danger

But Craig Grant disagrees. A tornado that moved through Urbana, Ill., in 1996, triggered many "garage door failures." It left an impression on Grant, who was then the city's building safety manager.

With the help of FEMA, Urbana studied the aftermath. One finding, Grant said, was that single-car-garage doors were inherently much stronger than wider, two-car-garage doors. One house with two single-car-garage doors survived the tornado, while houses surrounding it with wider doors had substantially more damage, added Grant.

"The width of the door makes a big difference," he said.

The study also found that using a heavier gauge of metal for the garage door track helped, as did simply using larger bolts and screws. In addition, the city found that using a stronger garage door, like those required in parts of Florida to resist 147-mph hurricane winds, added just $150 to a $500,000 house, said Grant.

"People would say to us, 'Oh, heck, you can't stop these tornadoes. They're going to get you,'" said Bill Rose, a research architect at the University of Illinois, who assisted in the study.

"[But] what you buy yourself isn't perfect safety, it's a reduction in the amount of damage."

Mike Kaszuba • 612-673-4388