How to Handle Efflorescence on Brick Chimneys

Efflorescence is a white material that appears on brick as a powdery mass of mineral. Efflorescence occurs when moisture moves through concrete or other masonry. The moisture picks up minerals, carries them to the surface of the masonry and leaves them behind in the form of tiny crystals on the surface as the moisture evaporates. The minerals themselves do no harm. You can simply brush them away.

Is Efflorescence Bad For Brick?

A small amount of efflorescence is common. But if the amount of efflorescence on your chimney is excessive, it may cause concern.

Some efflorescence could be caused by rainfall soaking into the brick. But more likely—and more serious—the problem is moisture in warm air from inside the house condensing on the chimney’s interior during cold weather. Or, even more alarming, your flue liner is cracked or broken and moist combustion gases from your furnace and water heater are leaking out onto the cold brick and condensing. This is a bad condition that will cause rapid brick-and-mortar deterioration.

What Should I Do If I See Efflorescence?

We recommend that you have your chimney inspected by a licensed heating contractor or certified chimney sweep before the heating season begins this year. Either one will tell you whether you must install a new chimney flue or liner or point to any other moisture source that may be causing the excessive efflorescence.