Masonry: Standing the test of time … and climate change

Photo courtesy Miller Thomson LLP.

Any construction project worth its mortar, so to speak, should be designed and built with longevity in mind. Masonry materials are selected their durability, strength and ability to withstand the elements. Year by year, however, weather conditions are changing due to global warming. How will climate change affect masonry projects and restoration in Canada? Recent studies conducted by the federal government and industry leaders have sought to answer that question.

ECC report

In 2020, the federal government published a report for the construction industry titled ‘Climate-Resilient Buildings and Core Public Infrastructure: An Assessment of Climate Change on Climatic Design Date in Canada.’ Prepared by Environment and Climate Change Canada (ECC) and made publicly available on that federal department’s website, the report assessed how changes in weather could affect standards established by the National Building Code of Canada (NBCC) and the Canadian Highway Bridge Design Code (CHBDC).

The report is divided into chapters on temperature, precipitation/moisture, wind and snow/ice. Each chapter breaks down how climate change affects these variables, which in turn may inform the design and construction of buildings and infrastructure across Canada, as set out in the NBCC and CHBDC.

In the chapter on temperature, for example, the report concludes it is “virtually certain” Canada’s climate will continue to warm in the future. Temperature is defined as a Tier 1 variable, suggesting the importance of considering its impact when designing new infrastructure, depending on the type of structure and the materials used.

Masonry will most likely be impacted by changes in freeze-thaw cycles.

CSA report

In 2021, the Canadian Standards Association (CSA) Group released a report prepared by Toronto’s York University titled ‘Climate Change Adaptation of Masonry Materials, Design and Construction.’ Using data sourced from the ECC report and other climate data and modelling, the CSA report provided specific recommendations for adapting masonry standards, based on the effects of climate change, and highlighted areas where further research is required.

Publicly available on CSA Group’s website, the report focuses on how climate change may impact the following standards that apply to materials, design and construction for masonry projects:

• CSA A82:14 (2018), Fired masonry brick made from clay or shale.
• A165 Series-14 (R2019), CSA Standards on concrete masonry units.
• CAN/CSA-A179-14(R2019), Mortar and grout for unit masonry.
• CSA A370:14 (R2018), Connectors for masonry.
• CAN/CSA-A371-14 (R2019), Masonry for construction for buildings.
• CSA S304-14 (R2019), Design of masonry structures.

The report finds masonry will most likely be impacted by changes in freeze-thaw cycles—caused by increases in average temperatures—and the corrosion of its connectors. To the extent such impacts “can be anticipated, they must be accounted for in the design of structures to avoid widespread failures and costly repairs.”

The report also points out the “deleterious effects of freeze-thaw action” are more commonly found in historical masonry. Poor insulation used to allow the indoor heating of such buildings to maintain the exterior brick at relatively high temperatures during cold weather, which would mitigate accumulating moisture. As historic buildings are updated with interior insulation, however, “rapid deterioration of the exterior masonry can ensue, if appropriate measures are not taken to ensure the masonry material is sufficiently durable.” Namely, attention must be paid to water-shedding detailing and air cavities to promote drying and minimize water permeation.

Another possible area of concern, according to the report, is the impact climate change may have masonry ties and connectors.

Further, many of Canada’s most populous cities have seen an increase in their annual driving rain index, a combined measure of rainfall and wind speed. Such precipitation has the potential to cause water permeation, which may in turn foster corrosive environments for ties and connectors, posing serious issues for the integrity of masonry cladding.

The report notes more study is needed to quantify the connection between changing weather and corrosion rates. It suggests CSA A370:14, Connectors for masonry, should be re-evaluated with regard to assessing the risk of corrosion.

Coming changes

While the climate in Canada continues to change, it is hoped a continued focus on and study of its impact on materials, design and construction will allow consulting engineers to stay ahead of the curve. The NBCC, for one, will see significant revisions in its 2025 edition based on recent climate change data and studies. Such revisions will likely mean changes to masonry standards and should mark an important step forward in maintaining buildings and other infrastructure.

Nathan Lean is a Toronto-based associate with Miller Thomson LLP. He practises in construction and commercial litigation and has represented a road range of stakeholders in the construction industry. For more information, contact him at (416) 595-7949 or nlean@millerthomson.com.