Chimneys serve multiple functions on many modern homes. They are an important part of the appearance of the home, as well as the conduit for smoke and fumes when you want a warm fire indoors. In some homes, chimneys may also house the vent pipes for oil or gas furnaces. A chimney is only as good as its masonry work, though, so damaged and crumbling mortar between the bricks can be a significant problem.
Missing and damaged mortar compromises the structural integrity of the chimney. This makes it more likely to collapse entirely if the problem is allowed to progress too much. For chimneys with metal liners, the collapse of the outer brick structure is likely the biggest concern.
Water can also make its way into the gaps caused by missing mortar, which can lead to moisture problems in the house. Even those that don't use their fireplace wouldn't want moisture and mold growth to become a problem in the chimney. Further, for chimneys with clay liners, this moisture incursion can cause damage to the liner and make the chimney unsafe to use for a fire.
Signs of Damage
Mortar damage can be obvious. If you notice missing chunks and loose bricks along the chimney, then there is obviously damage that needs to be addressed. Damage isn't always this easy to spot, though. Sometimes, the easiest way to tell if the mortar is reaching the end of its working life is to run your fingers along a couple of mortar joints. If sand and debris easily come loose as you do so, then it's time for repairs.
Certain things can speed up mortar decay. For example, ivy and other climbing plants growing up the chimney will slowly break down mortar due to the way the plants anchor. Trapped moisture from plants or other items kept up against the chimney can also speed up mortar decay.
Fortunately, chimney mortar can be repaired with a process known as repointing. Your chimney technician will carefully scrape out the damaged mortar between the joints. During this process, any cracked or damaged bricks may also be replaced.
Next, fresh mortar is carefully placed into the joints using a pointing tool. After the initial mortar dries, tuckpointing is completed. With tuckpointing, a slurry of mortar in the desired visible color is carefully layered onto each mortar joint. This gives the chimney a beautiful finish and the tuckpointing coat creates a protective barrier over the main mortar beneath.
Contact a chimney repair service if the mortar needs to be replaced on your aging chimney.