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How the Freeze/Thaw Cycle Affects Your Chimney

Here in the Richmond Region we see our share of winter weather. With average winter temperatures ranging from the low 30’s in the evening to the mid 50’s during the day, our season is milder than many other areas of the northeast. However, it’s this type of weather that makes chimneys in our area more prone to freeze-thaw damage.

Waking up to snow-capped roofs and chimneys is a typical winter sight. As the snow melts in the afternoon sun, the porous brick masonry surface absorbs moisture like a sponge. In the evening, when the temperature dips below freezing, the moisture turns to ice. The expanding ice crystals cause cracks in the bricks. As the freeze-thaw process continues, the spalling bricks become even more extensive. The moisture erodes the mortar leaving gaps in the joints. It also allows moisture to enter the flue and fireplace, resulting in severe damage to interior masonry walls and other parts of the system. Eventually, the freeze-thaw process can cause entire pieces of brick to separate from the chimney, negatively impacting its structural integrity. 

Rusted Metal Case Cover, Richmond, VASome of the common chimney damage due to the freeze-thaw cycle:

  • Masonry damage
  • Damaged Chimney Cap
  • Cracks in the Chimney Crown
  • Damaged Flashing
  • Water Leaks
  • Rusted Damper and other Metal Components
  • Leaning or Collapsed Chimney

Chimney Inspection

The best way to combat the freeze-thaw effect is to be proactive and have a professional chimney inspection. A basic level I visual inspection encompasses the entire chimney system, including the masonry, chimney cap, flashing, flue liner, and damper, to name a few. The review will determine whether any damages exist like a missing chimney cap, warped flashing, or spalling bricks, for instance. Making any necessary repairs as early as possible will help protect your chimney from more significant damage later.

Chimney Masonry Repair, Richmond, VAMasonry Repairs

Cracked or spalling bricks and gaps in the mortar joints can become a severe issue without prompt repairs. When the damage is minor and limited to small cracks, your chimney professional will use tuckpointing to repair it. A durable, waterproof bonding material fills in the cracks to repair the damage. It is expertly color-matched to the existing brickwork making your chimney looking as good as new. If the damage is more severe, it will need a partial or complete rebuild to replace the missing bricks and mortar.


Once you have a chimney inspection and made the repairs, you can waterproof the chimney to prevent future water damage. There are several waterproofing solutions on the market, but not all of them are best for masonry chimneys. It’s better to consult with a chimney professional rather than trying to do it yourself.  Your chimney professional will apply a vapor-permeable waterproof sealant that will repel rain and snow while allowing the masonry to breathe. Non-permeable waterproofing agents should not be used as they trap water vapors contributing to masonry deterioration.

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