What Happens to Chimneys Over the Winter

By Marge Padgitt

Winter is rough on any type of chimney- especially brick or stone chimneys. During the winter months, moisture penetrates the bricks, then freezes. When water freezes it expands and often causes part of the brick or stone to break off.  This is called "Spalling." The constant freeze/thaw cycles over winter can wreak havoc on masonry. Chimneys built with soft type brick are more susceptible to moisture penetration and spalling. 

Check the ground and roof for pieces of brick. This is the first indication that there is a problem. The area most affected will be the portion of the chimney above the roof line since that area is the most exposed.If you see spalling bricks or stones, call an expert to do an inspection and provide a solution. 

If the damage is not too severe, bad bricks can be removed and replaced, then an application of a professional water repellent sealer is recommended to reduce penetration of water. 

If the damage is widespread, the only solution is partial or complete tear down and rebuilding of the chimney. 

WATER is the primary problem when it comes to chimney damages! 

Rain water not only causes damage to bricks, but causes deterioration of the cement cap/crown. The cement cap is what keeps rain water out of the chimney interior where it can cause even more problems such as washing out mortar joints in the interior chimney and tile flue liners, deterioration of the smoke chamber and fireplace, and rusting of the damper.  

Hint: Do NOT paint or stucco over masonry chimneys - this only traps moisture inside the bricks and causes them to fail more quickly. 

FLASHING

Flashing that is poorly done, missing, or in need of repair can cause water leakage into the home and damage to rafters, joists, ceilings, and walls. Flashing should be checked each spring, and especially right after a roof repair or replacement is completed. 

The best way to avoid costly water damage is to keep it out and off of a chimney! 

Tips: 

• Have chimneys checked in the spring by a professional chimney sweep/mason
• Put a heavy duty stainless steel chimney cover on all flues to keep most of the rain out of the interior flues
• Repair or replace bad cement crowns/caps with a code required 2" drip edge to keep water off of the masonry below the crown where the most damage is usually found
• Have a professional water repellent masonry sealer applied
• Make sure J and Counter flashing is in good shape and sealed completely

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Marge Padgitt is the CEO of HearthMasters Masonry School and HearthMasters Restoration in Kansas City, Missouri.