Stevenson, MESc'17, a Structural/Wind Engineering PhD candidate, is studying how to make roofs on wood-frame houses more resilient to the impact of high winds, eager to apply her research in developing countries and disaster-prone regions.
"We've done so much research at Western on how to make the resistance of wood roofs better. It's really important to now make that information accessible to communities all around the world, so they can find solutions to prevent wind damage in ways that are most practical for them and most easy to maintain with the materials they have."
That's what prompted her to reach out to St. Thomas, Ont., builder Doug Tarry before his most recent humanitarian mission to San Lorenzo, Puerto Rico. She'd been following the progress of his Hope Agua Vita project in helping communities rebuild homes, restore electricity, and ensure a clean water supply after the devastation of Hurricane Maria. She thought she could offer some technical advice on constructing secure, sustainable roofs.
"We've done so much research at Western on how to make the resistance of wood roofs better."
"Doug's passion for the work and for teaching, along with the technical guidance we could bring to the people there, was really inspiring to me," said Stevenson.
So inspiring, she soon found herself signing up to go along.
It was an extraordinary opportunity to share her knowledge in teaching local residents about the importance of tied-down roofs in building more durable homes – and to work with Tarry to use their experience in San Lorenzo to show local builders how these measures could be easily adapted to build resilience back home.
* * *
Puerto Rico was still feeling the effects of Hurricane Irma – a Category 5 storm that slammed the Caribbean, Sept. 7, 2017 – when Hurricane Maria made landfall just two weeks later on Sept. 20, 2017. It was the strongest storm to hit the island in 80 years.
The National Center for Atmospheric Research in the United States observed the hurricane acted more like a 50-to-60-mile-wide tornado, raging across the state "like a buzz saw," destroying 87,000 homes and causing major damage to another 386,000. Many wood-frame houses were swept away, others lost their roofs, leaving their entire second floors exposed.
Damage is estimated at more than $100 billion, a crippling toll on an island where 20 per cent of the people still don't have water. The number of deaths associated with Maria continue to rise, currently surpassing 5,000.
The village of San Lorenzo lost its bridge, becoming even more isolated from help, food and water, and the place where St. Thomas builder Doug Tarry felt he could make a difference.
* * *
Photo: Hope Agua Vita Mission Leader Doug Tarry and Western PhD candidate Sarah Stevenson review building plans on a construction site in San Lorenzo, Puerto Rico.
How do you solve a problem like Maria? For Tarry, you start small, in a village of 800 people. Then you rally a team of expert builders, framers, engineers and labourers to help the residents of San Lorenzo rebuild. At the same time, you teach them the advanced building skills required to make their homes more hurricane resilient.
"The idea is if we can impact the people there, and make positive changes, it can spread," Tarry said, in terms of the rebuilding effort, and in creating much-needed jobs to address the shortage of skilled trades. "They do not learn about hurricane-resistant construction there and inspection programs don't exist."
The owner of Doug Tarry Homes also sees Hope Agua Vita's humanitarian mission as an opportunity for his team of expert volunteers to practise construction techniques – including the installation of hurricane straps and proper sheathing – and discover how to do it more cost-effectively and faster at home.
"People have said many times that nothing like this is going to happen in Ontario. Yet, just recently, we had winds relatively equivalent to Hurricane Hazel from the 1950s," he said, referencing Canada's deadliest and costliest hurricane and Toronto's worst natural disaster. "Yes, it can happen where we are and we need cost-effective ways to prepare for it."
"I was thrilled when I heard from Sarah," Tarry added. "I thought, ‘What a great opportunity to be able to talk to the future of our industry and to the people who are going to be looking at the research and figuring out how we're going to make this happen.'"
* * *
Photo: Western PhD candidate Sarah Stevenson on the ground in San Lorenzo, Puerto Rico.
"This is going to be a big learning experience for me," Stevenson said, before heading out to Puerto Rico. "I've never actually built a house before."
She had, however, done some mission work, having worked on a clean drinking water project in Honduras during her fourth year of her undergraduate degree in civil and environmental engineering at the University of Manitoba.
Inspired by a professor who told tales of being held at gunpoint as an engineer in Sierra Leone, unwilling to give up the building materials he was storing to teach locals how to build bridges, she thought, ‘I want that,' and returned from Honduras committed to keeping an international component in her graduate work and her career.
It was the reputation of Western's international program and Civil and Environmental Engineering professor Gregory Kopp, her eventual PhD supervisor, who was supportive of her global aspirations, which brought her to London to pursue her graduate studies.
With a focus on resilient housing, and as part of Kopp's research team, Stevenson's well-versed in evidence that supports the use of hurricane straps and extra, longer nails in the sheathing to hold roofs down in the face of severe upward winds.
She's also aware of the resistance many in the construction industry feel toward these measures.
"If we can teach a Puerto Rican homeowner how to tie their roof down properly, or how to seal their walls to keep moisture from coming in, that shows there's no reason why trained framers in Canada can't do the same," she said.
* * *
An exciting part of the week was showing the homeowners why clips, straps and sheathing are so important in building something that's even stronger so they won't be vulnerable when the next wind comes by.
During the week Stevenson spent as part the Hope Agua Vita team, she worked on three different houses, with the help of an interpreter to teach local residents the importance of resilience techniques in the construction of their homes.
"An exciting part of the week was showing the homeowners how wind loading impacts structure, where the weakest links in their houses were likely to be and explaining why clips, straps and sheathing are so important in building something that's even stronger so they won't be vulnerable when the next wind comes by," she said.
Working with one of the homeowners, Nancy, was incredibly powerful.
"We were literally working alongside her as she drove nails into her own home and from the short training session she understood what they were for. She worked very hard to prepare her home for resilience. She and her oldest daughter Grace were swinging hammers together, putting hundreds of the wind fasteners into the roof and wall frames."
It was equally rewarding to learn from and exchange ideas with the rest of the crew.
"With the framers, we had to find the balance between practical and strong and reiterate the importance of connecting every link in the vertical load path," she said. "Some of them were so smart about things that would work."
"Doug's really a champion in our area for wind resistance for Canadian homes," she continued. "I had the chance to work with him and point out links on one of the houses that needed to be strengthened, and he's totally onboard in adding extra hurricane straps, which is music to the ears of an engineer, because you don't often see that on a construction site."
Tarry appreciated the leadership she showed in her approach.
"Sarah kept us thinking a little lighter, but at the same time, she was willing to fight for what she needed as far as the structure goes," Tarry observed. "I like she's willing to stop, take a step back, and think outside the box and see if there's a better way for us to do it."
* * *
"The shared experience was really an amazing opportunity, to understand what we're dealing with, and offer a more resilient home," Tarry said. "Our question in bringing it back to Ontario was, ‘How do we do this cost effectively and get buy-in from industry?'"
He believes the construction details on the houses in San Lorenzo are applicable back home, but at a third of the material and labour costs of the estimated $1,000USD in upgrades the houses in Puerto Rico required to withstand the much higher wind loads.
"The hurricane strapping we used there wouldn't be needed. We can simply get away with some small clips that will do the same job."
For Stevenson, one of the most important things she gained from the trip was "seeing the practical implementation and how some of the things we recommend as engineers might not always be easy, or even realistic to implement."
Photo: Sarah Stevenson stops for a selfie with Nancy Morales and Luis Salgado during a home rebuilding project in San Lorenzo, Puerto Rico.
"One day we were working on putting the sheathing on the wall, and we usually recommend the nails go in, tightly spaced along the stud," she explained. "But when you're on the outside of the wall nailing in, you can't see where the studs are and with a high-impact nail gun it's easy to shoot right through and miss the structural member."
Issues like these were, and can continue to be, addressed by working together, and Tarry believes empathy and understanding goes a long way.
"My analogy on this is, if you're going to ask these guys to do it, it's really better for you to have one of two answers available: ‘Look, I've done this and it's not that hard, so please don't complain,' or, ‘Look, I've done this and it's hard, but it's important.'
"If they can have first-hand experience, and say, ‘I know I'm causing you pain. Here's the reason why,' it really goes a lot further than, ‘Those gosh darn engineers are making me do this. I'm really annoyed with them.'"
Stevenson is now even more energized to do research, having seen new questions come forth from her time in the field.
"We built a house that can withstand a Category-4 hurricane," she said. "Can we put sensors on it? Can we somehow measure if it is deflecting too much, or not enough? Can we build some test specimens for the next time something passes?
"The framers asked if they would have to put so many nails in," she continued. "They wondered if they could just glue it or whether there is a glue that can help keep roof together. It would be cool to test that in the Three Little Pigs lab where we could put the vacuum on it. It could be a seal, too, which would be very good."
Her experience in Puerto Rico will also serve her well as she continues her doctoral research in Cuba this fall, where housing remains a critical issue, and construction materials scarce, after Hurricane Irma left 10 dead and $13 billion in damages.
"I'll be working with professors and engineers down there, and I can bring this wealth of technical, and very detailed scientific information that Dr. Kopp and his students, and all the people who came before me at Western have acquired, and make it practical and translate it to the local people and have them actually come up with the solution. I want to learn from them what they do now, and what would work best for them in the future."