Tornado research uncovers risks for homeowners

Urbanization creating more awareness of potential threats
Thursday, May 11, 2023
By Rebecca Melnyk

Canada’s tornado risk is more widespread than once thought, according to a growing body of research that, for the first time, tracks the occurrence and aftermath facing property owners across the country.

The data, being gathered since 2017 by the Northern Tornadoes Project at Western University, comes as Canada’s rising population encroaches onto underdeveloped lands outside of cities. Just last year, the population grew by over one million, according to the latest record from Statistics Canada. With more density, comes more eyewitness accounts of tornadoes that would otherwise go undetected.

“As we spread out, things aren’t going to get better; things are going to get worse, and we don’t quite know what climate change is doing to that yet,” says Dr. Gregory Kopp, project leader and professor of civil environmental engineering at Western.

Unlike heatwaves, there is currently no proof of how global warming figures into the prevalence and power of tornadoes. Still, their location and timing are shifting course.

Tornadoes have long posed a threat to a stripe of the United States known as Tornado Alley, which spans across Texas, Oklahoma, and Kansas, but they seem to be edging eastwards into more densely populated areas. “There are also fewer days of tornadoes, but when they happen, it’s worse and there are more outbreaks with multiple tornadoes happening on a given day,” says Kopp.

In Canada, his colleague, Dr. David Sills, a professor in atmospheric sciences at Western and the project’s executive director, discovered big tornadoes are shifting later into the summer from the historical mid-July point into late August. “The earth’s weather system has many scales on it so we can’t quite attribute that to climate change yet,” Kopp says. Collecting more data, though, might one day reveal more evidence.

Tornadoes thrive in North America. Canada likely experiences more than any other country with the exception of the United States. The majority occur in Ontario, but severe weather investigations are tracking them in other regions, from British Columbia to Newfoundland and even beyond the 60th parallel in the Northwest Territories.

“Our goal is to try and find every tornado that occurs in Canada and then find all the ways that they affect us,” says Kopp. “We think there are a lot more happening than previously documented. Historically, Canada said we have about 60 tornadoes a year. Our current estimates are at least double that.”

During the 2022 season, the NTP captured 117 tornadoes, tying 2021 for Canada’s highest-ever single season on record.

If a tornado doesn’t hit anything, though, it’s challenging to find. Seventeen tornadoes in 2021 were just discovered this year after damage paths were identified through satellite imagery. Those events had occurred in heavily forested areas, from Saskatchewan to Quebec, so there hadn’t been any real-time civilian reports.

The first year the project launched, satellite imagery and radar imagery from storms revealed, after the fact, an outbreak of more than 20 tornadoes in Quebec that no one had experienced.

Much of the database information relies on social media tools—Twitter, Facebook, etc.—alongside radar networks and satellites that capture continuous images of the earth. “Tornadoes leave scars through forests and urban areas when they hit cities,” says Kopp. “But the remote ones we find with satellites.”

When they occur, field teams conduct surveys. Drones capture aerial imagery to determine the length of a tornado and what was destroyed. Structural engineers assess any damage of buildings that were hit.

To expedite the process and make it less human intensive, teams will soon begin using modern tools like LiDAR, an acronym for light detection and ranging, to create complete 3D computer models of damage.

Building better and smarter

As awareness increases, how concerned should homeowners be?

Tornadoes can occur anywhere thunderstorms erupt. They are random. In Ontario, they tend to occur along a wide and scattered path that follows the 401 corridor, from Windsor to Toronto to Montreal. There are also quite a few in the boreal forest, north of Lake Superior in cottage and fishing country.

The rotating columns of air come in all shapes and sizes, from ropey to wedge-like. When moving through dusty, dirty landscapes, they swallow debris that darkens their appearance. They are hard to see when wrapped in rain and come without visual warning at night.

A tornado’s intensity and wind speed are estimated by studying the damage it leaves behind, to which the Enhanced Fujita (EF) Scale assigns a rating. The scale comes with various damage indicators that range from milder (think flying eavestroughs and shingles) to complete destruction.

“EF-2 tornadoes are most commonly associated with damage in wood-frame houses, where the roof comes off in its entirety,”says Kopp. “When that happens, the structure is more vulnerable to collapse; people are very vulnerable if they’re inside.

“The most intense would be an EF-5. That’s when a wood-frame house that is well built is completely swept away; there is nothing left on the foundations, just bare concrete.”

Real-life examples include the EF-3 Goderich tornado in 2011 that demolished 35 residential buildings with peak winds between 253 and 330 km/h and left 283 buildings in need of repair, or the Barrie tornado in 2021— a set of EF-2 strength twisters in the range of 200 km/hour that called into question updates to the Ontario Building Code and tornado protection construction practices. An EF-4 tornado had previously ravaged the city in 1985, killing 20 people.

After the 2021 Barrie event, signs of posttraumatic stress disorder began to surface within the community. So, while the NFP wants to understand what tornadoes damage, they’re also starting to document the impacts on people.

“It’s a very stressful time when you lose your house,” says Kopp. “Even if you have insurance and you’re rebuilding it, there are still so many other things that will affect your life for a long time. We’re at the early stages of trying to understand that.”

In an event, townhomes and three- to five-storey wood-frame structures have similar vulnerabilities as detached wood-frame houses. This was the case in Ottawa in 2018, where low-rises on an apartment block had windows broken and walls collapse. “When the roof comes off, that’s when the walls are very dangerous,” says Kopp.

High-rise condos, on the other hand, are less vulnerable. The risk would be severe winds blowing loose furniture off balconies and equipment off roofs, and window breakage from debris and rocks, followed by rain and wind entry into units.

“But these buildings would be safe structurally. I can’t imagine a high-rise blowing over in a windstorm,” he says. “There’s lots of evidence that even in the strongest tornadoes steel-framed buildings tend to survive, but all the windows get blown out.”

High-wind service calls on the rise

Restoration companies that service buildings, including condos and townhomes, are seeing an increase in high-wind event calls in general. ServiceMaster Canada said significant May windstorms in 2018 and 2022 represented 38 per cent of its assignments in Ontario, compared to the average 14 per cent from 2019 to 2021.

This past February, consumer research from emergency restoration company First Onsite, found 52 per cent of Canadians are concerned about facing the effects of tornadoes and straight-line wind events known as derechos. Ontarians were second in the country (56 per cent), following Atlantic Canada (60 per cent).

“Recent events, such as the tornado in Barrie and the widespread derecho have certainly demonstrated the vulnerability of our housing stock,” says Jim Mandeville, senior vice-president, Large Loss Canada for First Onsite Property Restoration. “The intensity of these events, specifically, straight-line wind events, also seems to be escalating. We are also seeing the impact of these events hitting an ever wider geographic area.”

Damages were historically limited to roofs that were older and dilapidated, he observes. “What we are seeing now is damage to new roofing and exterior systems, windows, vehicles, and healthy mature trees. Obviously with these more extreme damages come drastically higher price tags in terms of monetary repair costs as well as the amount of time and interruption faced by homeowners and business owners.”

Insurance costs are another factor. A condo corporation has a policy to cover the external structure of the building and any common elements. Owners can also purchase personal condo insurance to protect their interior belongings. An event could trigger claims for both the corporation and individual owners.

John Cooke, president of ServiceMaster Restore of Ottawa and Daniel Loosemore, the company’s chief of sales and operations, said over email that as wind claims increase, the cost of insurance must be considered along with the self-insured retention.

“Where things become challenging is the increase in frequency of wind events that triggers claims activity,” they said. “If the self-insured retention is increased to keep premiums at acceptable levels and the reserve fund is low, any added financial pressure of the corporation is passed along to each owner through a special assessment.”

The building industry has been exploring ways to mitigate damage, while advocating for resilience. Canada has a good building code and code inspection regimes, says Kopp, but wind continues to be ‘a weak link.

While the National Building Code set out requirements for fastening the walls to the foundation following deadly tornado events in the mid 1980’s, a key oversight is holding the roof down, he explains. A roof left intact could ultimately preserve the walls of homes.

Roofs in Canada are strong, designed to handle heavy snow loads in winter to prevent collapse. “Wind is the exact opposite; it wants to lift the roof up,” he says. “Wood roofs are very light. What’s holding them down are the nails that go into the walls, and that’s the most vulnerable point of the structure during a windstorm.”

Simple measures are in the details, he adds. Hurricane straps in place of toe nails cost about $200 per home and keep the roof from flying off in EF-2 tornadoes. Wind-rated garage doors can be sourced from hurricane regions in the U. S. To keep the roof structurally sound and prevent rain and wind entry, longer nails could hold sheathing onto the roof.

Exterior building materials have come a long way in regards to harsh weather. As Cooke and Loosemore explain, in constructing asphalt composite shingles, a common roof material, a thicker, tear resistant base mat can be used to ward off the risk of damage.

“While these solutions cost more up front, many insurance companies see value in these building materials and often consider a reduction in insurance premiums,” they add. “In addition, the heavier base material coupled with better fasteners and improved bonding strips on the shingles reduces the damage caused by high winds.”

Windows are also evolving in areas historically susceptible to tornadoes. Laminated glass capable of withstanding high winds and flying debris could lower the risk from windstorms or, alternatively, metal roll-up shutters, which are often used in other parts of the world.

“These materials offer better protection and will likely become more common as the construction industry adapts further to our changing environments.”

To follow along with the Northern Tornadoes Project as it tracks and researches tornadoes across the county, visit:

Building Resiliency Recommendations

ServiceMaster Restore Canada

  • The building code is a baseline for building principals. Consider working with a designer or architect who has experience with building more resilient buildings.
  • Source and hire qualified and certified trades people.
  • Use products with severe wind ratings and ensure manufacturers specifications are met during installation.
  • Apply a full secondary water barrier beneath the roof cover to mitigate water damage.
  • Use hurricane clips on roof sheathing.
  • Fasten roof sheathing with screws rather than nails.

First Onsite Property Restoration

  • Installing reinforcements during the framing stage of construction can dramatically limit the amount of damage wood-framed buildings sustain during tornadoes and other extreme wind events.
  • Select more resilient roofing systems (specifically metal) which can also dramatically reduce the frequency and intensity of wind-related roofing damage.
  • Take extra care in maintaining roofing and exterior cladding systems on existing buildings to reduce damage. Any loose material should be repaired immediately. Roofing systems (specifically shingles) should be replaced once the tabs begin lifting.

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