A Homeowner's Guide To Chimney Cracks: Causes And Prevention

Your brick chimney may look solid as a rock, but chimney cracks can have a variety of causes and are not that uncommon. Left untended, chimney cracks can result in household fires, further chimney damage and even chimney collapse.

Causes of Chimney Cracks

Knowing the causes of chimney cracks will enable you treat conditions that lead to cracks and will also help you know what to look out for and where.

  • Construction Defects. Your chimney relies on solid construction and a sturdy foundation in order to maintain integrity. Movement or settling of the foundation can cause imbalances in the chimney as well as extra pressure in some mortar joints.
  • Moisture. Moisture leaks in and around the masonry can lead to damaging freeze/thaw cycles that produce cracks in the mortar and bricks.
  • Thermal Changes. Fluctuations in temperature and temperature differences between the exterior and interior of the chimney can cause expansion and contraction of the bricks, leading to cracks.
  • Chimney Fires. Chimney fires often cause extensive damage to chimneys, including cracking of the mortar and bricks.


Practicing good prevention is better than performing repairs. Follow these tips to prevent cracks in your chimney, and to prevent spread of already existing cracks.

  • Put a Cap On Your Chimney. Chimney caps are meant to prevent moisture from invading the flue and chimney. If your chimney is unprotected by a chimney cap, have this corrected as soon as possible.
  • Repair Leaks Immediately. Leaks of all kinds can lead to chimney damage. Roof leaks can cause moisture to build up inside the mortar joints and in the area around the chimney, resulting in frost cracks. Meanwhile, leaks around the home's foundation can cause the house to settle disproportionately on one side, causing the chimney to curve, bulge or lean, and that can result in cracks. Repair all leaks as soon as you become aware of them.
  • Make Foundational Repairs as Necessary. If your home does develop a foundational problem, have it fixed immediately.  
  • Get Earthquake Retrofitting as Necessary. If you live in an earthquake-prone area, earthquake retrofitting can better enable the chimney to withstand shaking from earthquakes, thus preventing damage to the chimney.
  • Perform Regular Inspections. Have your chimney cleaned and inspected on a regular basis. If it does develop cracks, these inspections will reveal the problem and empower the homeowner to make changes.

Masonry restoration is important for both homes and other buildings; having a professional inspect any potential issues will prevent damage from spreading or worsening.