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We do have a masonry expert coming to evaluate the nature of the pictured problem, but I thought I'd pose the question here to get some information and possibly, a second opinion.

There is some white mortar-like material oozing out of the joints of our brick chimney. What is the cause of this?

Thanks for looking.enter image description here

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1 Answer 1

up vote 5 down vote accepted

It is efflorescence. Water picks up minerals in the mortar and transports them until the water evaporates, leaving the minerals behind. Other than cosmetic issues, this is normally harmless, though if the process continues for a long period, enough minerals can be removed that the mortar sort of rots.

Only close inspection will indicate if the mortar is compromised. If it is, it's likely superficial and can be corrected by repointing. The deposits can be removed with muriatic acid. The mortar can be protected from more water incursion by applying any of various sealing products available.

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