The Crown: vital in protecting your chimney
Example shown is one of our limestone ledge crowns.
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A concrete crown forms the roof of your chimney and its job is to divert water away from the chimney structure. Water is your chimney's worst enemy, particularly in colder climates. The freeze-thaw cycle that causes expansion and contraction wreaks havoc on masonry, causing bricks to spall or flake, mortar to crumble, and concrete to crack. Since the crown is your chimney's first line of defense, it is also typically the first to show signs of wear. Any disrepair should be promptly addressed in order to prevent water intrusion into the interior chimney structure.
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Features of an effective crown
All of the elements of a chimney crown are designed to mitigate the effects of water on the integrity of the crown and the chimney itself. Some crowns will include all of the below features, others only some. Keep in mind that the crown's chief purpose is to shed water, and there are several ways to achieve that.
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Expansion jointAn expansion joint is created between the top flue tile and the concrete crown by wrapping the flue tile in a thin layer of foam and taping it in place before construction of the crown. The foam accommodates the expansion of the flue tile that occurs due to the warmth of combustion. Without the expansion joint, the flue tile would expand and crack the concrete, inviting water infiltration.
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OverhangJust as your roof overhangs your house so that rainwater does not pound the foundation, so does the crown overhang the chimney to prevent water from pelting the base of your chimney at the roofline. Water penetration through the roof can cause massive damage to your interior chimney and to your home. An overhanging crown helps prevent this.
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SlopeA properly sloped crown acts as an umbrella, maximizing runoff and preventing rainwater from pooling on top. The slope trends downward from the flue toward the outer edge of the crown, ushering water away from the chimney chase and minimizing its damaging impact.
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Drip edgeA chimney drip edge is a thin groove that is carved into the underside of the crown's overhang. Water that manages to make it to the underside of the crown will get only as far as the drip edge before falling to the ground. This protects against the destructive force of water running down the sides of the chimney and landing at its base.
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Water repellentThe final step in any chimney repair project should be the application of a masonry water repellent. Our masons choose ChimneySaver products, which are professional-grade and available only by professional application. Water repellent is superior to a waterproof sealant when treating chimneys, as it provides a breathable barrier without trapping moisture inside the brick and mortar joints.
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Wanna check out the different crown styles? Visit our chimney crown options page.
Free estimate + consultChimney repair can be a major expense, and the quality of workmanship has a direct impact on your home's safety and value. We know you want to get it right. Our estimate + consult is designed to give you the tools you need to make an informed decision about your chimney repair project.
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