Former Lethbridge College students’ roof wind worthiness project honoured as finalist for provincial award
05, Oct, 2022
EDMONTON, Oct. 5, 2022 – The battering Alberta homes sustained during heavy windstorms over recent years raises the question: what roof construction is the most wind worthy? A former team of Lethbridge College civil engineering technology students explored an answer for this as it applies to roof truss to top plate connection. For their efforts, they have been honoured as a provincial finalist for the Association of Science and Engineering Technology Professionals of Alberta’s (ASET) Capstone Project of the Year Award.
Roof trusses are the pyramid-shaped wooden triangles that fasten to the top part of the house frame, which is the top plate. Extreme wind events can severely compromise the integrity of roof connections with roof truss to top plate stability at particular risk of damage and failure during hurricanes, tornadoes and plow winds. Nine all-time wind records were set in Southern Alberta in January 2021. For example, wind gusts of 137 km/hour were recorded in Barnwell, Alberta, meeting the National Hurricane Center and Central Pacific Hurricane Center criteria for a category 1 hurricane.
Because keeping a roof over one’s head is of paramount importance, determining the best possible roof truss to top plate connection method was the goal of former Lethbridge College students John Burt and Shay Wirll for their Capstone Project.
Wind loads or uplift forces are considered during engineering, design and construction of structures. With various roof truss to top plate connection methods available to the construction industry, each type comes with its claims of connection strength. The team tested the following connection methods: traditional nailing with 3-8D nails; hurricane ties (H1.81z Simpson Strong Ties); and structural threaded screws (FrameFast six-inch structural threaded screws). Each sample was individually loaded into and tested by Lethbridge College’s Universal Testing Machine.
The former team’s research found that the FrameFast six-inch structural threaded screw provided the strongest tensile connection strength when compared to the traditionally nailed and hurricane tie roof truss to top plate connection methods. The structural threaded screw had on average a connection strength that was 54.1 per cent higher than the traditionally nailed connection and 8.9 per cent higher than the hurricane tie connection.
“This is good news for the construction industry. By increasing the strength of the roof truss to top plate connection, the cost of construction will be reduced because less material, labour and time are needed to make the connections,” said former team member Burt. “The structural threaded screw connection is also safer to install. Installation of structural threaded screws can be completed from floor level without the need to use ladders to work at heights or enter the rafters of the structure.”
“In the great tradition of the ASET Capstone Project of the Year Award finalists, the former Lethbridge College team’s project reflects a commitment to public safety,” said ASET CEO Barry Cavanaugh. “Ultimately, this former team’s findings could have the potential to influence standard future approaches to roof truss to top plate connections.”
The former Lethbridge College team’s project is one of eight finalists named by ASET for the 2022 Capstone Project of the Year Award. The winning project will be announced later this year.
The Capstone Project of the Year Award was established by ASET in 2017 in response to overwhelming member interest in back-to-school stories about Capstone projects undertaken by teams of engineering technology students from NAIT, SAIT, Red Deer Polytechnic and Lethbridge College as part of their end-of-program requirements.
ASET is the professional self-regulatory organization for engineering technologists and technicians in Alberta. ASET currently represents over 17,000 members, including full-time technology students, recent graduates and fully certified members in 21 disciplines and more than 120 occupations across a multitude of industries.
Michele Penz, Calico Communications for ASET