June 26, 2014 by Canadian Underwriter
Much of the damage from the recent tornado that struck Angus, Ont. could have been prevented with inexpensive building changes, according to a storm damage assessment completed hours after the storm passed.
The EF2 tornado hit the area on June 17, and damaged more than 100 homes. Just hours later, Western University engineering’s Storm Damage Assessment Team, supported by the Institute for Catastrophic Loss Reduction (ICLR), was on the ground to work with Environment Canada to assess the tornado damage.
The team then worked to map the storm track and document damage to about 100 homes, 10 of which had complete roof failures, according to ICLR.
“Canadian homes are well built, but roofs continue to be vulnerable to strong wind,” Greg Kopp, leader of the forensic research team with Western said in a statement.
“With small changes in building practices we can substantially reduce the risk that an EF2 tornado destroys a new home in Canada,” he noted.
“Along with doing what the building code requires, we need to invest just a few hundred dollars extra in each home to avoid the kind of structural damage we saw in Angus. These changes would add much less than 1% to the cost of a new home.”
Some low-cost prevention measures include use of hurricane straps, metal bands that wrap around trusses and connect to walls.
“These costs, perhaps, a dollar apiece and can largely eliminate the risk of roof failures from an EF2 tornado,” he said.
Other considerations include using longer nails in roof sheathing, like 2.5 inch, rather than the code minimum 2 inch nails, placed every 6 inches apart rather than every 12 inches. “The longer nails and tighter nailing pattern more than doubles the strength of the roof sheathing against uplift forces, and the added costs are minimal,” Kopp noted.
Kopp and ICLR have partnered to discuss emerging wind engineering research with Canadian homebuilders and on proposals that have been made to the National Building Code of Canada.