How the Freeze-Thaw Cycle Can Damage Your Chimney

The freeze-thaw cycle that occurs during winter weather conditions can severely damage your chimney. Any prior masonry damage can increase the severity. A chimney inspection, especially after winter, is vital in determining whether the effects of the freeze-thaw cycle caused any chimney damage.

Winter can be very challenging for chimneys because it is the time of year that exposes it to two potentially harmful effects: rain and ice. Combining the two creates the winter phenomenon known as the freeze-thaw cycle.

Freeze-Thaw Damage

Brick masonry chimneys are porous and will absorb moisture through existing cracks in the surface. The masonry, which is composed mostly of cement, sand, and lime, becomes soft and spongy when soaked with moisture. When it freezes, the expanding ice crystals create larger cracks in bricks and mortar. Rising temperatures lead to thawing. The ice crystals melt, and these more significant cracks will fill with moisture during the next precipitation event. Since winter weather in the Tennessee Valley, can be erratic and unpredictable, the freeze-thaw cycle can be a daily event at certain times during the season.

Spalling Bricks

Over time, the freeze-thaw effect will cause bricks to crack or spall. As the problem progresses, chipped bricks will lead to entire pieces falling to the ground. The eroding mortar will also leave gaps in the mortar joints. It can destabilize the chimney, eventually leading to a complete collapse. Catching the problem early through annual chimney inspections is essential to prevent significant damage and expense.

Water Leaks

Any time you have masonry damage, there is a potential for water leaks in the chimney. Exterior water damage is bad enough, but interior water intrusion is very damaging. It can quickly accelerate its deterioration. It can soften the interior masonry causing cracks in clay tile flue liners. When the flue liner is compromised, it increases the risk of fire and exposure to carbon monoxide. It also severely reduces the heating efficiency of your fireplace or woodstove, increasing energy costs. Chimney leaks can also promote the growth of mold and bacteria during the warmer, humid months of summer.

Combating the Freeze-Thaw Cycle

The first step to stopping the damaging effects of the freeze-thaw cycle is to have a professional chimney inspection to determine whether there is chimney damage. Then the next step is repairing the damage. Tuckpointing is a common technique that masons use to fix minor masonry damage. The final step is to apply a waterproof sealant that will repel rain and snow while allowing the bricks to breathe. Using the wrong sealant can create more damage. So, it’s best to hire a chimney specialist to apply the correct coating for your chimney. Keep in mind that the waterproof sealant will need to be re-applied every few years to maintain its effectiveness.