When I look at the recent news images of the houses hit by tornadoes – roofs torn off, framing joists and trusses scattered like toothpicks across backyards – I have to ask myself: Why aren’t we building better? Why aren’t we building houses that will withstand severe weather, protect the families who live in them, and last?
You’ve heard of the three little pigs, who built houses out of sticks. The big bad wolf had no trouble blowing those houses down. But he couldn’t beat the brick house. (And we’re talking a solid brick house, not a stick-framed house with a brick facade, by the way.)
I get it that a F5 tornado is powerful enough to tear up pretty much everything in its direct path. But F5s are rare. And a properly built house should withstand a smaller tornado like the more common F1 or F2, which is what struck last week north of Toronto.
I think it’s possible to design and build a tornado-resistant house. Construction built to seismic code is common in areas prone to earthquakes. I’ve built a house in Los Angeles that complied with it. These buildings are designed based on many years of experience in seismic areas. So, why isn’t it done in areas prone to tornadoes?
If you live in tornado alley in the U.S., or even in Canada – we get an average of 80 tornadoes every year, believe it or not – you need to build smarter.
Basically, a tornado is wind blowing in a cyclonic direction, and that wind exerts an upward force that lifts up whatever it encounters. The path of a tornado is unpredictable – it can move fast and erratically – but the type of force it exerts on a building is not. Neither is the kind of damage it will do. The upward force tears off roofs or floors, or lifts the house off its foundation. That’s why mobile homes are so vulnerable – they are tossed around like toys.
The force of the wind will find the weak points in the house’s construction. The roof flies off – or even the entire floor – taking the homeowners with it. Or, the roof is torn off, and the exterior supporting walls collapse because they are now more vulnerable to lateral wind loads.
But where a house is bolted down to its foundation, and the roof is properly anchored to the walls, it might be damaged but it won’t be destroyed. If the same anchorage that’s used in seismic zones were mandatory in tornado zones, a house could survive an F2 with minimal damage.
And it wouldn’t cost much. What’s the cost of a few anchors and bolts and ties? Of glue and screws, instead of nails? I guess builders play the odds; the likelihood that your home will ever be hit by a tornado is very small, so they don’t factor that possibility in when they are designing and constructing homes. Especially when that would be building above code.
I’d love to design and build a house that would piss off a tornado. I wouldn’t build it out of straw or sticks. I’d build it out of bricks or concrete – designed low to the ground. And I’d anchor it and do it above National Building Code standards.
You think of heavy rain when you think of hurricanes, but most of the damage is caused by wind. So, the exterior envelope of the house needs to be built to withstand 200 km/h winds. That’s not that hard to do, believe it or not. Choosing the right building materials, and assembling them properly will make all the difference. Don’t just nail sheathing to the frame – glue and screw it and you’ll increase the strength and wind resistance dramatically.
Hurricane ties are required by code in areas hit by hurricanes in the U.S. (though I’d bet they aren’t in the Atlantic provinces, where they are often hit by tropical storms), but they won’t do the trick alone. You’ve got to use them as part of a properly designed wall assembly. The whole wall structure has to be tied together – from the roof and top plate through to the sill plate, all the way down to the foundation.
Keep your home from being blown away by the big bad wolf.
In my experience rebuilding after Hurricane Katrina, I was shocked to find most of the houses that were destroyed weren’t on footings, they were just sitting on grade, or on concrete blocks. Why is that? It doesn’t make sense. A house is not a boat, it’s not supposed to float. Anchor it. Secure it to the ground so it doesn’t float away in a flood.
And, why wouldn’t you elevate the structure above the flood zone to protect both the residents and their belongings? And while you’re at it, build with materials that can get wet and will dry out – without moulding – after the storm passes.
What about building a house that won’t burn down? When I was in L.A. a couple of years ago, I could see the wildfires spreading along the horizon, taking street after street of homes. You’ve seen the news footage in the aftermath of these fires. What’s left standing? Chimneys, the concrete, brick and stone structures. So why aren’t they building houses from concrete? Yes, the furnishings could burn, but the basic house structure will still stand. And, since concrete is non-combustible, it’s not going to allow the flames to easily spread from house to house.
So why aren’t we building geographically or regionally appropriate houses?
I think that smart building of the future will take into account regional climate and geography. Houses need to be built sustainably, and in a design appropriate to local conditions.
Thoughts?
Original Source: http://www.nationalpost.com/story.html?id=1936618
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