For the purpose of this article, it is important that we differentiate between weather, climate, and extreme weather events. Weather refers to day-to-day conditions with respect to temperature, precipitation, humidity, pressure, etc., whereas climate is the average weather for a particular region over an extended period of time. Climate change is increasingly being tied to a rise in the frequency and intensity of extreme weather events, such as:

• Heavy rains and floods
• Heavy snow falls
• Strong winds and tornados
• Thunder and lightning storms
• Thermal extremes
• Large wild fires

The effects of climate change are already having an effect on our current building stock, and it presents a significant challenge to future projects. In many recent structural engineering investigations, our analyses have demonstrated that the design and construction of impacted and failed structures met the minimum requirements outlined in the current Ontario Building Code. Yet, under these extreme weather conditions, the structures nevertheless failed. That is because building codes rely on historical data – data that no longer represents the conditions a building will be required to bear.

The main factors introduced by climate, and those that directly impact the safety and service life of our built environment, are:

• Higher wind speeds, gusts, and more frequent microbursts
• Thicker and denser snow accumulations
• Deeper frost line**
• Heavier rains and increased flash flooding

Wind

In the past several years we have investigated total roof failures resulting from microbursts – where wind speeds exceeded those specified in the current building codes by over 35%. We have also observed a sharp increase in the collapse of walls and roof trusses during construction, caused by strong winds, where the collapsed member was not properly braced.

Precipitation

In western Canada, we have been called upon by the insurance industry to investigate partial and total roof collapses under the weight of heavy snow accumulation. In the majority of these cases, snow accumulation records from Environment Canada demonstrated higher snow weights than the minimums specified in building codes.

Water leakage and flooding damage claims are also on the rise. Any minor flaws in roof construction become great vulnerabilities under the intense and heavy rains Ontario has been experiencing in these past few years.

Temperature

Currently, building codes require the foundation be placed at least 4 feet beneath the ground surface to be below the frost line. However, new record low temperatures are causing a thicker ground layer to freeze. From our frost heave investigations, we have found ample anecdotal evidence to suggest that the frost line is moving deeper. In these frost heave cases, the frozen ground expanded, causing damage to the foundation and superstructure.

Adapting to Change

The impact of climate change is now well recognized by the Canadian Commission on Building and Fire Codes. A huge effort is underway to update the climate data in the National Building Code of Canada to account for extreme weather events. The new design values for climate data are expected to be in effect by 2020*. Future construction will certainly benefit from these changes, however, it is left up to the judgment of the practicing engineers to select appropriate load intensities for the repair and renovation designs of existing structures. Designers must always remember that building code requirements are merely minimum values to meet, not to aim for.

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Yasser Korany, Ph.D., P.E., P.Eng., LEED AP

Yasser specializes in structural forensic investigation and construction litigation support. His engineering practice spans more than 25 years, and he is a licensed professional engineer in Ontario, Alberta, British Colombia and the State of Michigan. Throughout his career, Yasser has applied his unique combination of laboratory and field experience to identify the cause of structural distress and failures for institutional and commercial facilities, residential buildings and parking garages. Yasser is also a LEED® Accredited Professional. This accreditation signifies Yasser’s expertise in providing sustainable engineering solutions that minimally impact the environment. Prior to joining Origin and Cause, he was a Professor of Structural Engineering at the University of Alberta where he taught structural analysis and mechanics courses, and provided forensic engineering consultancy services in Alberta.