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Time to Think About Sealing Your Chimney Crown

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A chimney crown, also called a chimney wash, is the top portion of a masonry chimney. The crown covers and seals the top of the chimney, extending from the flue liner to the edge of the chimney. Its downward slope directs water from the chimney flue to the edge of the crown itself. A masonry chimney usually has an inadequate crown if it’s made from a common mortar mixture.

Re-sealing a chimney crown - before and after

Re-sealing a chimney crown – before (left) and after (right)

A higher-quality crown is normally done by a chimney specialist who understands the type of mortar and concrete that is best for this tough job. The crown is formed or cast to provide an overhang that projects at least two inches beyond each side of the chimney. The chimney flue liner tile should project at least two inches above this crown. The crown needs to withstand abuse from weather elements without deteriorating, chipping, or cracking.

Sealing the chimney crown involves applying a flexible coating of acrylic to protect the crown from water infiltration. If a crown becomes cracked, water can enter the chimney and, as the crack widens over time, more water is permitted access. Eventually, the amount of water entering the chimney exceeds the amount that can evaporate and the deterioration process begins. If damage is caught early, the crown can be repaired and a masonry sealer can be applied to the chimney.

The rubber-like coating of the sealer fills in cracks in the crown. Since it is flexible, it can expand and contract with the chimney. It also directs water away from the top of the chimney, serving as an umbrella. This material can be applied to other exposed masonry surfaces to prevent water from entering through the chimney sides.

If your chimney crown has not been addressed, have a chimney inspection to identify whether sealing is necessary. A darkened upper masonry chimney, flaking and chipping of bricks, or dark mold on a stone chimney are typical indications that the area requires repair. Addressing damage before it becomes serious will save time and money.