The mortar joints of a chimney become damaged due to harsh weather conditions, particularly excessive amounts of water. Moisture can even damage rock masonry, when water gets in due to weakened mortar joints. “Tuckpointing” is a repair process which stops the destructive process and provides numerous benefits.
While bricks on a chimney last about a century, mortar has a much shorter lifespan. Depending on how exposed the masonry is to excess water and other harsh conditions, mortar lasts about 25 years. It’s sometimes highly recommended that homeowners install a cricket, which is a compact diversion roof that prevents the chimney from being deluged in rainy weather. The layout of the roof and the position of the chimney affect how much or little water drainage contributes to erosion of the mortar joints.
When mortar joints become damaged, the most cost-effective action that a homeowner can take is to repair affected areas via tuckpointing. The alternative is to allow the mortar joints to deteriorate to the point that the chimney collapses, which makes a complete rebuild necessary–of course, the cost of a rebuild is far greater than the cost for repairs.