Most people think that since a masonry chimney is made of durable masonry products and mortar that it is virtually indestructible. Unfortunately, this belief is far from the truth. Take the Grand Canyon for example. As water eroded and formed the Grand Canyon, it can also deteriorate mortar joints in a chimney. Fast forward to today where there may be acid rain, pollution and debris from factories. This can lead to a more rapid deterioration of the chimney verses the conditions of 100 years ago.
Meanwhile, the chimney flue can be exposed to the following: heat, acidic residue, cresosote, and debris, which can take a toll on the flue and mortar joints. If moisture combines with a residue, it can bring it through the residue through the mortar joints. Often this may now be a damaging acidic residue. One obvious sign that this is happening is the evidence of efflourescence. This is where white mineral salts are carried by moisture through the wall of the chimney as in the photo, below.
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Masonry chimneys are usually built by skilled craft-workers. When properly built, in average masonry construction, mortar joints are serviciable for 35 years or more when properly installed. Masonry units such as brick or block usually have a service life of 100 years or more. However, a chimney tests this to the extreme.
When a chimney inspection reveals cracked, deteriorated or missing mortar joints, tuckpointing restoration is necessary to repair the chimney and maintain the integrity of the system.
Posted by Karen Lamansky, Director of Marketing