House Whisperer: 6 Things Your House Is Trying To Tell You Something You Shouldn't Ignore
Efflorescence is the white material that appears on brick. It occurs when moisture moves through masonry. That moisture picks up minerals and leaves them behind in the form of tiny crystals.
The minerals themselves do no harm, and a small amount of efflorescence is common. But heavy efflorescence on your chimney is a cause for concern. It’s a sign of moisture inside the chimney – and when that moisture freezes, it can slowly wreck the chimney from the inside out.
Even more alarming, your flue liner could be cracked or broken, and deadly combustion gases from your furnace, fireplace or water heater may be leaking into your home.
Cracks in the crown allow water in (top left). Water that gets inside the chimney through cracks in the crown can cause efflorescence and damage the bricks.
Seal the crown (bottom). Small cracks in the crown can be sealed with an elastomeric masonry sealer, but a crumbling crown will have to be replaced. Smear on the sealant by hand, then smooth it with a brush.