Why is only the bottom row of my brick spalling in Barrhaven?

Why your brick is spalling only at the bottom row is something a mason needs to see at the wall.

A National Research Council building digest (CBD-30) notes that frost damage depends on "the degree of saturation with water, the rate and number of times of freezing, the strength and elastic properties of the material, and the nature of the pore structure," and that "below a certain degree of saturation no damage occurs." The same digest notes that salt spalling "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 few things a mason will look at:

• whether the mortar joints at that course are open or crumbling, letting water in
• whether there is flashing and weep holes at the base of the veneer directing moisture out
• whether the brick at that level is a different unit than the rows above
• whether white staining or efflorescence is present alongside the spalling

What to ask for in writing before any work starts: which bricks are being replaced and how many, where the matching brick is coming from, how mortar colour and joint profile will be matched, how the crew will control silica dust when cutting out old units, and what cleanup and disposal are included. Ask whether the quote covers an inspection of the flashing and weep holes at the base of the wall, since the Code's flashing and weep holes sit at the base of a veneer wall.

Start with a mason who can look at the wall in person, because the pattern you are describing has more than one possible explanation and the right repair depends on the right diagnosis.