If you had a direct hit by a tornado there is no one that can help you but the Red Cross, your family and church, your insurance company and the contractor you carefully choose. But if your neighbor was plastered and his debris hit your home or your roof was damaged, then there were precautions you could have taken, and still might, to mitigate the amount of collateral damage your roof and roof structure sustained.
Starting with the roof and working down and into the framing, the first thing I would suggest is hand nailed roofing. Roofing nail guns drive nails at up to 952 mph. Enough said if you've ever held a fiberglass shingle or been hit in the head by anything going over 500 mph.
Next comes the felt. If it is not flat, the wind has something to grab a hold of. ( “This is the sort of English up with which I will not put.”Churchill). There are specialty flat laying felts like Roofer's Select or Shinglemate that help keep the roof surface flat.
Professional starter strips, rather than 20 year shingles turned around upside down and backwards help with the first course and rake edge by giving a stouter material with self seal near the edge. They also help prevent ladder damage to the edge.
Six nailing will increase your wind warranty from the manufacturer.
Now we go down into the meat of the home to find weaknesses. The first is old weak plywood badly nailed and improperly spaced. If coated or hot dip galvanized nails weren't used, the shingles might stay on but the plywood they are nailed too might be up there with Toto on the way to Oz. Lack of spacing causes buckling, giving the wind a place to grab.
Thicker plywood, or OSB, will help just by being heavier and having more wood to keep the decking nails implanted. Might as well as use Techshield and get the energy saving.
Hurricane clips, not like on new construction along the coast, which we can't install without removing your brick or siding, but the kind that connect the rafter to the top plate. These little inexpensive items give over 50% more uplift protection. That might just do the trick if it is just a drive by tornado.
Lastly, believe it or not, ventilation. Ventilation makes everything last longer. Paint, roofing, insulation, decking, your money, your health, your air conditioner, your marriage, not necessarily in that order. By keeping everything strong and dry from excessive humidity, ventilation keeps the entire structure younger.
Jon Alan Wright
Jon Wright Roofing, Siding, and Windows
1915 Peters Rd., Suite 310
Irving, TX 75061