Three roofing materials that can survive high winds
Tom Shafer | Improvement Center Columnist | September 13, 2013
If your home is severely damaged in a weather event - such as the destruction brought about by Hurricane Sandy - your primary thought when rebuilding is probably to make the house as impenetrable and stable as possible. With proper building techniques and the right materials, your home can in fact be made very weather-resistant. A key part of a weather-resistant home is the roof. Care must be taken to select the right materials for your area, especially if your region experiences high winds.
First, it's important to understand how roofs come apart during storms. Your roof has two water barriers: the shingles, tiles, etc. on top, and beneath that, the sheathing. The sheathing is the fastened to the rafters, and it acts as a surface for your top layer. A roof is destroyed when the uplift from wind pressure lifts the sheathing off the frame. Generally speaking, the sheathing material should be applied using at least 5/8" thick exterior plywood or, alternatively, an exterior composite material. It is best attached using 8d ring shank nails, which are very difficult to pull out of wood. Placed close to each other - no more than six inches apart - these nails will help to keep your roof held tight during extreme weather.
Given that your sheathing is put directly on the rafters, you also want to ensure your rafters are secure. For high-wind areas, rafters should generally be tied to their supporting walls with metal straps, such as the ones made by Simpson Manufacturing
Once you know your rafters are secure and your sheathing is solid, you can explore the many roofing options you have. Three of the most popular types of roofing that can be made to withstand hurricane winds are shingles, metal roofing, and concrete roofing forms such as tiles.
- Shingles are probably the most well-known and most popular roofing material. However, shingles made to be installed on inland construction using a typical three or four nail fastening application may not be suited for high wind areas. Does that mean you can't use them on your roof? Definitely not. It's just a matter of selecting the right shingle and the right application. Shingles are made of either a composition material of paper and wood fibers or fiberglass. Fiberglass shingles are strong and can do well in high-wind areas. They are made by being soaked in asphalt and embedded with fine granules of stone. Be aware that higher wind areas need special shingles, such as those manufactured by Owens-Corning that use their SureNail® Technology. Most shingle manufacturers require at least six nails driven straight and flush to hold during high wind. Owens-Corning (and SureNail®) requires only four nails because of the special woven fabric in their shingles. You may be tempted to say "if four nails are good, six are better," but actually, four nails means fewer holes in the roof deck and fewer opportunities for water to intrude into the home.
- Clay tiles have been used as roofing material for centuries. If you want to use clay tiles and you live in a windy region, be aware they require exact installation. Without proper installation, they can be one of the most dangerous roofs in high-wind areas. That doesn't mean you have to cross them off your list immediately. There are many benefits to these tiles: concrete or clay tiles are energy efficient, they're available in many colors, and they're very water resistant. So what makes them so dangerous? Clay tiles are known to be blown off roofs, turning them in to projectiles that can easily penetrate windows, doors, and even walls of surrounding buildings. Foam adhesives, like the ones manufactured by both Dow and Poly-foam, are recommended for installation to avoid some of the dangers associated with clay tiles. With adhesive, each tile is bonded to the deck. Adhesive is used in place of mortar and has superior holding power during high-wind events. The first row of tiles should also be secured with ties similar to those used to secure framing members of the home. In addition to being attached with adhesive foam, they should be screwed into place to at least a one-inch depth.
- Metal roofing has long been used in windy areas, but again, it must be applied very precisely. If applied correctly, metal roofs can be a great option because they are very water-resistant. Two types of metal roofs may work for your region: a standing seam roof, which draws the water up and away from the roof during wind, or a water shedding metal roof, which is made with metal shingles and overlapping ribbed sheets of metal. While these are generally nailed into place, if the roof is being installed in a high-wind area it should be screwed instead. Most manufacturers have requirements for spacing of the screws for their particular roof, and their instructions need to be followed exactly. For long-lasting dependability, the clips and screws used should be stainless steel.
Costs for wind resistant roofing are higher than costs for average roofs. The total cost you can expect is dependent on the quality of the roofing and the amount of wind-resistance your roof requires. For a low-wind resistance improvement, you should budget about $1000 extra. Where a moderately high wind is expected, the cost might increase to as much as $3000. In high wind areas you may need to spend closer to $5000.
As strong and sturdy as your roof is, remember that it won't be able to withstand high uplift pressures if your doors and windows aren't protected. Wind protection is a house-wide concern. While you're considering your roofing needs, you might want to evaluate the state of your windows and doors to ensure you're as protected as possible.