Signs that mortar froze after a late-fall Ottawa repair?

A National Research Council building digest (CBD-123) describes what to look for: "the familiar crows-foot pattern on the surface of a mortar joint indicates freezing," and "shelling of the mortar surface and general crumbling or powdering of mortar are evidence of advanced deterioration due to freezing."

The Ontario Building Code (9.20.14.1) sets the rule: mortar and masonry shall be maintained at a temperature not below 5°C during installation and for not less than 48 hours after installation, and no frozen material shall be used in the mortar mix. If temperatures dropped below that threshold during or right after the work, the signs above are what you would expect to see.

What to look for when you examine the joints:

• a fine network of cracks across the face of the mortar
• mortar that flakes or shells away in thin layers when touched
• powdery or crumbling sections

Keep in mind that a second digest (CBD-30) says salt damage is "very similar in appearance to that produced by frost action, and in many cases it is difficult to determine which mechanism has caused it." A mason looking at the wall in person can tell you whether the affected joints need to be cut out and redone.

If the repair was done under a written contract, check what warranty was provided and whether it covers failure caused by cold-weather conditions. Get any warranty terms in writing before agreeing to remediation work.

If you want a local mason to have a look, the request form on this page sends your details to Ottawa masons listed in the Ottawa Construction Network directory.