Question 1

Could a water repellent coating hurt my Ottawa brick?

Accepted Answer

A water-repellent coating can cause damage to brick, and a National Research Council building digest (CBD-30) explains the mechanism: when a vapour-permeable but water-repellent membrane is applied to the outer face, salts are deposited behind the surface layer, and the force of crystallization can cause the skin to spall. That spalling can look very similar to frost damage, which makes it hard to tell after the fact what caused it.

Question 2

Should I seal the brick on my Ottawa house?

Accepted Answer

Sealing brick is a decision worth pausing on, because a sealer can cause the very damage it seems to prevent. A National Research Council building digest (CBD-30) explains that with a vapour-permeable but water-repellent membrane on the outer face, salts are deposited behind the surface layer and the resulting force of crystallization can cause the skin to spall. What that means in practice is that the condition of your brick and mortar matters before anything goes on the wall.

Question 3

Will efflorescence on my new Barrhaven brick fade by itself?

Accepted Answer

We found no source that says whether efflorescence on new brick fades by itself, so a mason looking at the wall is the one to say. A National Research Council building digest (CBD-123, 1970) notes that efflorescence "is usually at a peak during the late winter months." Ask the mason where the water carrying the salts is coming from.

Question 4

Cleaning century brick on an Ottawa house, what's safe?

Accepted Answer

There are too few published sources on brick cleaning methods to give a general answer, so a mason looking at your specific wall is the one to say what is safe for it. A National Research Council building digest (CBD-30) notes that applying a vapour-permeable but water-repellent membrane to the outer face of brick can cause salts to deposit behind the surface layer, and the resulting crystallization pressure can spall the skin off.

Efflorescence & Moisture

Could a water repellent coating hurt my Ottawa brick?

Should I seal the brick on my Ottawa house?

Will efflorescence on my new Barrhaven brick fade by itself?

Cleaning century brick on an Ottawa house, what's safe?