Could Angus tornado damage have been prevented?
Damage could have been greatly mitigated with some simple building fixes to roofs, Western University researcher says
By: Joseph Hall Toronto Star
As Gregory Kopp toured tornado-ravaged homes in Angus, Ont., this week, his thoughts turned to depressingly familiar terrain.
“This could have been prevented,” says the Western University civil engineer.
“Lots of what we saw in Angus … a lot of that could have been mitigated in my opinion, a lot of that.”
Indeed, for a couple of hundred dollars a dwelling, Kopp says, builders could have staved off some of the worst of Tuesday’s twister wreckage, which left 100 houses damaged and 300 people homeless.
And he should know. Kopp is the lead researcher at the London school’s Three Little Pigs project – a towering facility near the city’s airport that can create storms inside of biblical proportions.
And since the facility opened in 2006, Kopp and his colleagues have been subjecting full-sized and scale model homes to the most devastating wind conditions imaginable.
What they found – and have shared with government and building industry officials to little avail – is that small, low-cost measures can protect family homes from the most common tornado and hurricane damage.
The fixes — most of which are more easily and cheaply installed during construction — centre mainly on the homes’ roofs.
During hurricanes or twisters, violent winds blowing over the peaked roofs of homes act like air flowing over the curved wings of an airplane, Kopp says, exerting an upward lift on the structures.
“That’s kind of counter-intuitive for builders because they think of holding the roof up with walls … but in a windstorm you have to hold the roof down.”
That, Kopp says, can be easily achieved during construction.
In particular, he says, the installation of what’s known as “hurricane straps” — small pieces of metal that bind the roof truss to the top of the wall — can help enormously.
“And they are about a buck apiece and they’re pretty easy to put in,” Kopp says.
“So for each house if you did that it’s really only a couple of hundred bucks but it makes the connections there much, much stronger. If we fixed those, a lot of the damage would disappear.”
But this simple fix, even for home construction in tornado-prone areas, has been resisted by builders, who see it as money out of pocket, Kopp says.
“Now you get into the crux of the matter; in my experience they (builders) absolutely will not do this unless they’re told to do it,” he says.
“So to me, the only way we could implement it is by a building code change.”
It isn’t their cost, but their absence from that code that dissuades builders from installing the straps, says Joe Vaccaro, CEO of the Ontario Home Builders’ Association.
Vaccaro says builders rely on the code as the gold standard for their duties and materials, and that they would need permission to install any structural safety device that it didn’t approve.
When asked in an email if the province intended to include hurricane straps in the code, municipal affairs and housing officials replied only that they were not included in the latest, 2012 edition, but that builders could install them if they chose.
“The Ministry frequently receives suggestions for changes to the Building Code, and all submissions receive consideration,” the email said.
Even if hurricane straps continue to be rejected, however, Kopp says more and longer nails holding roofs to walls and together could help in high winds, which approached 180 km/h Tuesday evening in Angus.
Kopp says replacing two-inch nails holding down plywood roof sheeting with 2.5-inch versions, for example, can double binding strengths.
“And difference in cost is probably pennies a house,” he says.
He also says more nails are better than fewer. In Ontario, the building code requires three nails be used at each connecting point between roof trusses and wall tops.
In Angus, however, Kopp says many of the felled trusses he examined only had one nail.
“I didn’t find one code compliant connection in fact,” he says.
Vaccaro says any new home being built in Ontario has to be signed off on at seven stages by a local building code inspector, including the framing stage, where the nail count would have been assessed.
And the ministry says there are no penalties under the building code act for faulty work and that homeowners should seek their own legal counsel, or contact Tarion, which administers the province’s new home warranties act.
Beefed-up connective measures work best in weaker tornados like the category EF2 storm that hit Angus, Kopp says.
Direct hits by stronger twisters — like the EF5 monsters he can replicate in the Three Little Pigs facility — would basically doom any house that is not built to nuclear reactor specs, he says.
Yet most of the damage left by such killer twisters — like the one that levelled much of Joplin, Mo., in 2011 — is caused by winds that surround the funnel clouds.
And these destructive, vortex-churned winds blow at EF2 levels and can often be foiled by stronger roof bindings, Kopp says.
But binds must be installed during construction; retrofitting measures requiring ripped out drywall and tens of thousands of dollars.
For existing homes, one of the few affordable tornado buttresses available is the installation of stronger garage doors, Kopp says.
Garage doors penetrated by the missile-like debris borne in tornados can let winds into the space within and basically blow the roofs off from below.
“And those roofs go and they hit neighbouring houses and you get a cascade of damage.”