The Freeze/Thaw Cycle on Your Chimney

The freeze-thaw cycle can have a devastating impact on masonry chimneys in Maryland. While you are firing up the fireplace to stay warm and cozy, rain, snow, and ice are accumulating on the exterior brick surface.

Throughout the winter months, temperatures in the Frederick and Carroll County area often rise and fall above and below freezing repeatedly. The brick surface is porous and soaks up moisture like a sponge. As the temperature drops below zero, the soaked moisture turns to ice. The expanding ice crystals cause bricks and mortar to crack. When the ice crystals thaw during the day, these larger cracks fill with moisture during the next precipitation event and freeze again at night.

This freeze-thaw process repeatedly continues throughout the winter season. These ever-expanding cracks eventually result in the crumbling of entire pieces of bricks and mortar erosion. Gaps in the joints where mortar used to be may also be noticeable.

The chimney is in danger of a partial or complete collapse if the freeze-thaw effect repeats unabated for several seasons. It also increases the risk of fire and carbon monoxide poisoning.

Protecting your chimney starts with a chimney inspection

Annual chimney inspections can help uncover minor winter damage before it develops into a significant problem. During a basic level 1 inspection, a Certified Chimney Sweep® conducts an exterior and interior visual examination of the entire chimney system. The technician will be able to spot spalling or missing bricks, gaps in the mortar joints, chimney crown damage, water leaks, and other issues that can occur during a long, cold and wet winter. Making timely repairs will not only prolong the lifespan of the chimney but will also ensure your wood-burning or gas fireplace operates safely and efficiently.

Tuckpointing to repair your chimney

Chimney masons use a technique known as tuckpointing to repair chimneys with minor masonry damage. A chimney mason will use a bonding compound to fill in the voids of spalling or cracked bricks and missing mortar that resulted during the freeze-thaw cycle. The repair is expertly color-matched, restoring the chimney to its previous condition before the damage. Chimneys with significant brick damage may require a partial or complete rebuild to restore its structural integrity.

Applying a waterproof sealant to prevent water damage

Applying a waterproof sealant can help protect your chimney from water damage. However, any masonry damage must be repaired for the repellant to be effective. Since using the wrong waterproof sealant can cause masonry damage, it is highly recommended homeowners use a licensed and qualified chimney professional. Chimney professionals know to use a vapor-permeable sealant that will repel moisture while enabling the bricks to breathe. Also, the waterproof sealant should be re-applied every few years to maintain its strength.