Chimney Cracks? Common Cracks and How They Occur

Here Is a List of Typical Causes of Cracks in Brick Masonry Chimneys and Flues…

Cracks in a brick masonry chimney  may be caused by improper original chimney construction. This damage may also appear on concrete block constructed chimneys.

    • Improper construction: failure to leave air space between flue line and masonry chimney sides – if the mason does not leave an expansion gap surrounding the clay flue liners as they are set into the chimney during construction, and as the flue heats up during use, the expanding flue may crack the surrounding brick.
    • Water leaks: at the chimney top (a missing rain cap, a faulty chimney cap  seal), or at the chimney sides (defective flashing, wind-blown rain, open mortar joints) can send water into the chimney structure, where in freezing climate,s frost can lead to cracks to the chimney itself or to its flue liner.  And since water and frost can also cause surface spalling of brick or concrete block chimneys, look for that as well.
    • Chimney movement: a chimney which is set on a defective footing or an improper foundation (more incorrect chimney construction) or a chimney which was not properly secured to the building may lean, bend, or curl, leading to cracks that usually appear in the mortar joints.
    • Thermal expansion cracks in chimneys: a masonry chimney may crack from thermal expansion, or its internal flue may crack from thermal expansion, if the chimney was not properly constructed, failing to leave space for movement as the chimney interior heats up when in use.
    • Mechanical damaged chimney cracking: a masonry chimney may crack due to stresses from a chimney-mounted antenna, satellite dish, or from an earthquake or nearby site blasting stresses.

These are a few of the most common reasons you may spot chimney cracks on your structure. It is highly important, that if you see ANY of these, that you contact your local CSIA Certified specialist to come inspect it properly for you to prevent and/or repair any damaged areas: 817-791-4606