As hurricane winds pass over a roof, they create powerful upward-sucking forces. If shingles or other roofing materials are not securely attached, they will simply peel off, opening avenues for water to infiltrate. In the worst-case scenario, roof sheathing pulls off too, compromising the house's structural integrity while it exposes the inside to the elements.
For new construction or additions, the roof should be built to wind-rating codes for your area, with 5/8-inch plywood decking fastened securely to the roof framing. Waterproof the seams with self-adhering flashing tape, cover the sheathing with roofing felt, and top the whole thing off with shingles rated for wind and impact resistance. Typically, these are a laminated sandwich of fiberglass and asphalt, held down by six nails in a special pattern. In addition, glue down all shingles within 2 feet of the roof's vulnerable outer edges with an asphalt cement. Look for the MP1 rating on the label, the highest industry standard for asphalt adhesives.
With its extra-large head, beefy ring shank, and spiral threads at the top, the HurriQuake
nail is designed to increase a roof's resistance to uplift forces by as much as 100 percent. In tests, it didn't pull out even when subjected to wind gusts of up to 170 mph. (Greater shear strength makes it handy in earthquakes, too.) And that added protection will only run you about $15 for a whole house.
What You Can Do NowBracing:
Hip roofs, in which all four sides slope toward a central ridgeline, are naturally more wind-resistant than gable roofs. One way to strengthen a gable roof is to brace the end walls, which are the most vulnerable to uplift.
Get up into the attic and nail or screw a pair of 2x4s in an "X" pattern—one extending from the peak of the gable to the bottom center brace of the fourth truss, and the other from the bottom center of the gable to the top center brace of the fourth truss. Use 3-inch-long wood screws with a ¼
-inch-diameter shank, or 16d galvanized common nails, and reinforce the new braces wherever they meet roof members with 1-inch galvanized-steel straps.
If your roof is framed with rafters, you can strengthen it by adding collar ties. "Adding collars will improve a roof's ability to take wind load," says John Knezevich of Thornton-Tomasetti Group Engineering, in Fort Lauderdale, Florida. Brace every pair of rafters by running a long stud from one side of the roof to the other, three-quarters of the way up the slope of the rafters (imagine the letter "A"). Fasten it at each end with long wood screws and galvanized-steel straps, effectively creating a bridge across the inside of the roof.
Get up into the attic and run a half-inch bead of construction adhesive along each rafter or truss where it meets the plywood roof sheathing above. "A good, thick bead down the edge on both sides of the rafter will tighten everything right up," says This Old House
general contractor Tom Silva. This simple step will roughly triple a roof's protection against being torn off by the wind.
Hurricane straps—1-inch-wide galvanized-steel ties that extend from the stud to the top plate and over the truss or rafter—tie the roof and walls together. While it's not easy to retrofit them (there's little maneuvering room in the attic at the edge of a pitched roof), it can be done by a skilled professional, who may need to remove a section of roof sheathing or siding to gain access. Attach a strap at each roof-to-wall connection.