Applying Brick Sealant to a Chimney Applying Brick Sealant to a Chimney
Applying brick sealant to a chimney can be a very time consuming job and also very dangerous, so you should be well prepared and think all the steps through before beginning. There is a varying opinion on whether or not applying a waterproof sealant to a brick chimney is even necessary. Others swear by it and say you must do it to preserve your chimney, especially if you have a fire place.
How Water Damages a Chimney
Water damage due to chimney leakage is a billion dollar business, but that takes into account bad flashing, missing mortar, cracked chimney caps and no damper. Chimneys stand well above the roof line, so they take a lot of abuse from the elements. Over time this can loosen or destroy the mortar and cause bricks to shift and pop out. Water leaking into a chimney can cause mold issues, which is an expensive problem to fix. If you have a fireplace, the water mixing with creosote or ash forms a chemical similar to lye, which is highly corrosive. Since bricks are porous they attract and trap water. During the freeze/thaw process the water expands and contracts. This will cause your chimney to loose mortar, bricks to fall out and misalign. Chimneys can actually twist and warp out of shape when this happens. Applying brick sealant to your chimney can help prevent these problems by filling in small cracks and crevices and making the bricks and mortar less porous.
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