Facts About Chimney Cracks

chimney cracks, winter chimney maintenance, concord New HampshireThe chimney is an impressive structure built to withstand the high temperatures of a roaring fire in the fireplace. It also takes the brunt of Mother Nature all year long, combatting wind, ice, storms, and humid summer conditions. As a result, the chimney will need maintenance and repair from time to time. The appearance of chimney cracks is a sign that shouldn’t be ignored.

Freeze-Thaw Conditions in Winter

One of the most common causes of chimney cracks occurs during the winter when fireplaces are used the most. Masonry chimneys are porous materials. They absorb moisture as the snow-covered bricks melt when temperatures rise during the day. As nighttime arrives and temperatures dip below freezing, the absorbed water freezes inside the bricks. The ice crystals expand, causing tiny cracks on the surface. Hardly noticeable at first, the small cracks continue growing as the freeze-thaw cycle repeats throughout the winter. Eventually, gaps in the mortar joints appear along with cracked, chipped, and even crumbling bricks. The mortar erosion can also loosen the bricks and ultimately separate from the structure.


Lightning strikes are a more common phenomenon than many homeowners may realize. According to the National Oceanic and Atmospheric Administration (NOAA), more than 30 million ground points are struck by lightning annually. Since lightning often strikes the highest point, the chimney is a potential target. Lightning contains billions of watts of electricity, generating 18,000 F to 60,000 F of heat. Evidence of lightning striking the chimney includes burn marks, gaping holes in the structure, and damage to portions of the chimney where it was struck.  Contrary to popular myths, lightning can strike the same area twice.


Many homeowners may not realize it, but the chimney is the heaviest structure attached to the home. Settling occurs when the weight of the house or chimney sinks into the ground. Poor soil conditions or weakening due to moisture intrusion or pests can increase the severity of settling. When settling occurs, cracks can develop in the bricks and the chimney foundation. In more severe cases, the chimney may even start to lean or separate from the house.

Chimney Cracks need maintenance, Sullivan County, New HamshireFooting Problems

The chimney should be built on a solid footing to support the weight of the structure. A foundation that is too small or is built on poor soil conditions can result in structural problems, including cracks and leaning. The freeze-thaw cycle can also cause cracks in the cement footing.

Poor Chimney Construction

Chimneys should be built to industry-standards by experienced chimney masons per state and local building codes. A chimney that is poorly constructed or constructed with inferior materials can cause cracks, water leaks, and other safety issues. Also, there is a certain amount of space that is required between the flue line and chimney. Failure to adhere to these standards could also cause cracks in the flue liner, increasing the risk of fire and exposure to toxic fumes.

If you notice any chimney cracks, contact your local chimney professional or Black Moose Chimney to schedule a chimney inspection. Our chimney professionals will repair your chimney so you can continue to enjoy your fireplace safely.

First Thing

John RantaJohn Ranta
17:01 22 Mar 24
They arrived on time, worked quickly and showed me the results. Prfessional throughout. jr
william greenwilliam green
23:21 14 Mar 24
Really helped me out can't say enough good things highly recommend!!!! The young man that came to my home was very knowledgeable and friendly great attitude all around answered all my questions and left me stress free best of all left no mess.🤙🏻🤙🏻
Michael Dell'OrtoMichael Dell'Orto
18:39 14 Mar 24
Jaime ConleyJaime Conley
17:13 14 Mar 24
Sarah GilliattSarah Gilliatt
01:46 13 Mar 24
A very thorough and careful job done! Thank you.
Larry CookLarry Cook
15:11 07 Mar 24
I wanted to give 5 stars but they are very busy which meant I had a good wait for both the inspection/cleaning, then for a quote on repairs and then for the repairs. Their prices seemed a little high to me but I have nothing to compare with as they were highly recommended by someone I trust and other companies had plenty of negatives reviews which kept me from getting additional quotes. I am happy with the work and they promptly returned to fix a mistake that had been made. Chris the inspector, Jennifer in the office, and Alex and his repair crew were all pleasant and took the time to answer all of my questions. Alex and his crew even took their shoes off (it was winter) before entering my house without even being asked! So if you are not in a rush and want to ensure you chimney is as safe as possible then I think you'll be happy with Black Moose.
Rebecca DeFuscoRebecca DeFusco
22:35 21 Feb 24
After a recent sweep of our chimney, it was discovered that our flue tiles were cracked. Black Moose techs were hard working, detail oriented and professional! Nice jobs guys! See you next year for my cleaning!
Karen CKaren C
14:52 14 Feb 24
Excellent I highly recommend Black Moose Chimney and Stove; Kelly and Liam are awesome, they did a great job. Extremely professional, arrived early, went through everything with a fine tooth comb ensuring pellet stove was thoroughly cleaned. They also were respectful of my home, conscientious and cleaned up after themselves. Made sure stove worked prior to leaving and told me to call promptly if anything came up afterward. Will definitely use them again.
Denise ClarkDenise Clark
16:32 31 Jan 24
We've had Black Moose clean our chimney for a number of years.But recently, we had an emergency situation at our home involving our chimney & oil furnace flue, which was caked full of soot from a malfunctioning furnace. They came & cleaned out both flues in no time, even going up on the roof with snow on it! They cleaned up after their work in the interior rooms where the oil furnace and the woodstove are located. Great work. Reasonable prices. Very nice people. You can't go wrong with Black Moose.
Joe GJoe G
18:30 24 Jan 24
Goods: The technicians know their business, very efficient in cleaning/inspection along with cleaning up after the 'dirty work'.Others: Communications could be more effective. Despite early coordination about scope of work (multiple flues within same chimney) the estimate provided did not reflect this and the final invoice was significantly more than the estimate provided.Quote for follow-on chimney relining was significantly more than that offered by other companies in the area (and far more than neighbors experienced for similar work accomplished by other companies)