Windows covered with plywood or shutters are a sure sign of hurricane preparation in Florida, but here's the plain truth:
Approximately 80 percent of residential hurricane damage starts with wind entry through garage doors, according to the Federal Alliance for Safe Homes.
"The larger the door, the more vulnerable it becomes to high winds," said Jeff Burton, building codes manager at the Institute for Business and Home Safety in Tampa. "A doublewide is more vulnerable than a single."
Garage doors are vulnerable because they cover a big opening. Most garage doors are made of relatively lightweight galvanized steel, with or without polyurethane or polystyrene insulation, to conserve expense and make them easier to raise and lower. (Garage doors may also be made of aluminum, fiberglass and wood.)
Because of that size and weight, the garage door — which is held in place only by the tracks — is one of a building's weakest points. Compounding the matter, garages tend to be at the corners of the house, where wind pressure and suction are greatest.
When high winds assault a garage door, it buckles in the middle into a V. The rollers pop out of the tracks and the door fails.
Your goal, therefore, is to reinforce the door and the tracks, Burton said. You don't want the door to be sucked out of the tracks, and you don't want the tracks to pull out of the ceiling or wall to which they're attached.
So how do you reinforce that big, vulnerable and comparatively flimsy entrance to your home?
Homeowners have a couple of options.
First, look at your existing door. If it was installed after the new building codes went into effect on March 1, 2002, it should meet the requirements for wind load in your area. A label or certification seal on the door will indicate this.
If it's an older door, you can have a new door installed that meets hurricane codes. The requirements vary, depending on which wind zone you're in. A retailer can help you determine which door is right for where you live. A door must withstand higher wind load along the beaches (and therefore will cost more) than one that's installed in inland Hillsborough County. A new doublewide door costs around $1,200.
Even then, you're not buying guaranteed safety. A door is only as strong as the garage it's attached to. The strongest door in the world won't help if the garage is flimsily constructed.
Retrofitting existing doors
Retrofitting an existing door involves giving a door rigidity against pressure and suction. This is done by installing permanent horizontal trusses made of galvanized steel. Then on hurricane day, on a double door, you add a vertical post to increase its strength still further. Retrofitting a door costs about half the price of a new door.
The second step is to add more brackets that attach the tracks to the walls.
"Attach the door better to the building and add horizontal reinforcements," said Bill Houser, owner of Genie of St. Petersburg.
"You've got to have the horizontal for the vertical to work correctly," Houser said. "Some people will buy a vertical post for $116 with no horizontal reinforcement. It helps to some degree, but the door will just bend around that post if you haven't added structural reinforcement" with the horizontal trusses.
The goal, he said, is to prevent the door from bowing in and out. If there's a deflection of more than about 3 degrees, gaps start to open up around the edge of the door and high winds can enter the garage — exactly what you're trying to avoid.
The horizontal trusses can add 80 to 100 pounds to the door's weight, so the springs must be adjusted accordingly. Otherwise the door may rip out of the tracks. This is a job for a professional; those springs are dangerous.
Simply attaching plywood to the inside of the door may void the warranty or damage the motor or the track because the door is too heavy to operate properly.
Don't fall for the urban legend that your garage door will be strengthened if you park a car inside the garage with the front touching the garage door. (Variation: Park a second car outside, nose to nose with the car inside.) If this really worked we'd never see another collapsed garage door. It's not true.