The Effects of the Freeze/Thaw Cycle on Your Chimney

When your masonry chimney was initially constructed, it was designed to last decades. However, rain, wind, extreme swings in temperature, and other weather events can accelerate its deterioration, exposing the porous structure to moisture. While age and cold weather are mostly to blame, a lack of routine inspections and maintenance is also a contributing factor.

Repairs to Chimney Damage Amherst, NHWinter Weather Damage

As precipitation saturates the porous brick masonry, the moisture will seep through any cracks or crevices. It absorbs the moisture softening the concrete, sand, and lime that mostly comprise of the bricks. It also weakens the mortar that holds the bricks in place. Its erosion leaves gaps in the mortar joints between the brickwork.

Freeze-Thaw Cycle

When cold winter temperatures fall below freezing, the moisture that has already been absorbed turns to ice. The expanding ice crystals cause the softened material to crack and crumble. Rising temperatures thaw the ice crystals trapped inside the bricks. More winter precipitation fills these cracks and crevices where it will crystalize once again when the temperature dips below freezing. The continuous freeze-thaw cycle further widens the cracks and erodes the mortar resulting in larger pieces of chipped bricks. As the damage progresses, the sight of missing bricks in the chimney is evident. It can even lead to a complete chimney collapse.

Chimney Crown

Winter weather can also damage the chimney crown, especially if the chimney lacks a chimney cap. Heavy rain and snow can cause hairline cracks in its surface. The freeze-thaw cycle can accelerate the damage and allow moisture to seep in between the flue and interior walls. 


The flashing can also be at risk for winter weather damage. The thin metal strip seals the gaps between the chimney and the roofline. When the flashing is warped or damaged, moisture can penetrate through any gaps. Spotting water stains on the ceiling near the fireplace is often an indicator of a flashing problem rather than a roof leak. Repair or replace the flashing as soon as possible to avoid roof damage.

chimney Inspection Concord, NHChimney Inspection

The Chimney Safety Institute of America (CSIA) recommends annual chimney inspections. An annual chimney inspection is your first line of defense to protect your chimney from the damaging effects of winter weather. The review will assess the condition of your chimney and recommend the necessary repairs to any damaged areas.


Waterproofing the chimney can also help prevent water intrusion. It is necessary first to repair any cracked or missing bricks and mortar, otherwise, waterproofing will not be very useful. For best results, it is recommended that only a licensed chimney professional should apply the sealant. Chimney professionals use a vapor-permeable sealant that shields against rain or snow while allowing the masonry to breathe. Other types of water sealants can trap moisture further deteriorating the brickwork.


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)