Is it a problem that my weep holes are blocked in Kanata?

Blocked weep holes are worth addressing. They sit at the base of the air space behind your brick veneer, and their job under the Ontario Building Code (9.20.13.8.(1)) is to let moisture that collects in that cavity drain to the outside.

The Code requires weep holes spaced not more than 800 mm apart at the bottom of cavities and veneer air spaces, including above lintels. When they are blocked, water that finds its way behind the veneer has nowhere to go. A National Research Council building digest (CBD-30) notes that frost damage depends on the degree of saturation with water, among other factors, and that below a certain degree of saturation no damage occurs.

A few things a mason will look at on your wall:

• what is blocking the holes (mortar droppings, insect nests, debris, or a previous repair that filled them in)
• whether the flashing beneath the weep holes is intact and directing water outward
• whether any brick near the base shows staining, spalling or mortar deterioration that points to water sitting behind the veneer

On sealers: a National Research Council building digest (CBD-30) notes that with a vapour-permeable but water-repellent membrane on the outer face, salts can be deposited behind the surface layer and the resulting force of crystallization can cause the skin to spall. Ask the mason before applying anything to the wall face.

Ask the mason to check the surrounding mortar joints and flashing at the same time, since the Code's flashing (9.20.13.6) and weep holes (9.20.13.8) work together to direct water out of the air space. Get the scope of work, the mortar type and colour match, and any warranty in writing before work starts.

The most useful question to put to the mason before you agree to anything: what condition is the flashing behind those weep holes in, and will the quote include inspecting and reporting on it?