What temperature is too cold for mortar work in Ontario?
What temperature is too cold for mortar work in Ontario?
Mortar work is too cold under Ontario's Building Code (9.20.14.1) when this rule cannot be met: mortar and masonry shall be maintained at a temperature not below 5°C during installation and for not less than 48 hours after installation. No frozen material shall be used in a mortar mix.
That is the Code's requirement. It sets no outdoor air temperature; it sets a threshold that must be met at the work face, which can mean heating and enclosing the work when the air is cold. The Code (9.20.14.2) also requires that the top of uncompleted masonry be completely covered with a waterproofing material whenever work is not in progress.
NRC building digest CBD-123 notes that set-accelerating and anti-freeze admixtures "should not be encouraged" in cold-weather masonry work.
A few things worth confirming with any mason quoting cold-weather work: how they plan to maintain the 5°C minimum at the wall (heated enclosures, blankets, propane heat), how long they will keep that heat in place after laying, and how the uncompleted work will be covered overnight. Get the method in writing as part of the quote.
Before you sign, ask the mason how the mortar and masonry will be kept at 5°C or warmer for the 48 hours after each day's work.
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Masonry IQ -- Built from the Ontario Building Code, Ontario regulations and City of Ottawa sources and real construction experience. Answers are for informational purposes only and are not a professional assessment.
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