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What Causes Cracks in a Chimney?

Cracked Chimney Repairs - CTAre you wondering what causes cracks in a chimney because you’ve discovered that your chimney is damaged? You are not alone.

Homeowners are often aware that chimneys can last a century or more, but they may not realize that it is common for chimneys to become damaged and beginning cracking and splitting. There are many potential causes of a cracked chimney, though excess moisture is ultimately the primary culprit.

Improper Construction

Anytime there is chimney movement, the result can be cracks in the masonry and mortar. There are various mistakes during construction that can lead to premature damage. For example, a gap of air space should exist between the flue lining and the chimney. If there is no gap, the expansion of the flue that occurs when the fireplace is in use can crack the surrounding brick. Another example of poor construction is if a portion of the chimney leans and/or is unsupported, such as in the attic.

Tension Caused by Wind

There are times when wind creates cracks in a new chimney. The mortar that holds masonry together is strengthened over a course of weeks and months. Strong winds can cause tension on a new chimney, resulting in cracks. The way this particular problem can be avoided is by installing steel rods inside the chimney structure.


When moisture gets into a chimney system, many different types of problems can occur, including cracks in the chimney. The exterior of the chimney is generally protected by being properly constructed, with a chimney crown and mortar that prevents moisture from getting between the masonry. If an excess amount of water flows onto a chimney because of the way the roof is constructed, it’s important to have a roof cricket built. A roof cricket is a ridge structure that diverts water away from the chimney.

When moisture gets into the masonry, movement is ultimately created that results in cracks. The movement is usually caused by freezing and thawing cycles. If you ever notice piles of debris falling around your chimney, it is an indication that there is moisture causing the masonry to pop and flake off on the face of it.

Dangers of a Cracked Chimney

A cracked chimney should not be ignored because of potential dangers. One threat is that the chimney structure could begin leaning and collapse altogether, which could cause injury and the need for a costly rebuild. Another danger is that the fireplace may not function properly. Toxic fumes that are supposed to exit through the chimney could seep into the home, if the chimney flue is also cracked.

Contact our Chimney Professionals

Fixing Moisture Problems in a ChimneyThe construction and re-construction of a chimney should be done by a professional who understands the importance of a properly built structure. If your chimney or your flue lining is cracked, contact us today. Our trained, certified professionals are experienced and skilled at chimney repair and chimney rebuild. We also provide tuckpointing services, which involves replacing damaged mortar, in order to keep moisture out of the masonry.

Contact our chimney professionals today for help and advice on what you need to do if you have a cracked chimney.

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