Q – We have noticed a white chalky substance on the outside of our brick chimney and also on the brick walls in our basement. Do you know what it is and how to get rid of it if it’s serious?

Pauline – Chicago

 A – I’ll bet this is something many people can relate to, on either newer or older masonry work.

It’s called efflorescence, a mineral deposit, similar to Epsom salts. It shows up when moisture dissolves the salts in the brick or the mortar joints. After the water evaporates, you’re left with the white salts on the surface of the brick. Efflorescence is usually a temporary, cosmetic issue on newer brick and can be washed away by rain or rinsed off with vinegar. But on older masonry, it may be a sign that moisture is getting behind the brick.

If you have a situation where these white salts are a constant problem, then there is a definite need to find and address a moisture issue. Something as simple as increased ventilation might cure the problem for an interior wall. On your chimney, it may be due to a damaged chimney cap, so that is what I would check first.

*TIP: Washing it off and applying a masonry sealer is the worst thing you can do and a common mistake I run into. This will only lock in the moisture and speed up the decay of the bricks.

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