Chimney systems are deceptively simple. For example, a simple stone column actually consists of several different components. They all need care and maintenance in order to keep your fireplace burning safely and efficiently. One of the most important – yet often ignored – chimney components is the chimney crown.
What is a chimney crown?
The chimney crown is the concrete or masonry slab that sits on top of the chimney structure, sealing around the flue. Quality chimney crowns slope gently down and away from the flue to prevent a buildup of moisture on top of the chimney crown. This helps prevent chimney leaks and water entering the chimney system.
What causes chimney crown damage?
Improper installation or construction often causes chimney crown damage. Because of their location and exposure to moisture and the elements, it is extremely important that chimney crowns are built using quality construction practices and materials. If not, the crown can deteriorate prematurely.
While bricks and mortar are ideal building materials for the chimney structure, they are unsuited for use in a chimney crown. Mortar-based mixes are significantly more susceptible to water damage; moisture, sun exposure, and changing temperatures can cause mortar-based crowns to crack and age.
Crowns built without an adequate slope deteriorate prematurely. When the chimney crown is too flat, moisture from rain, sleet, snow, and other sources can pool on top of the chimney instead of running off onto the roof. Over time, this can cause cracks and holes to form in the chimney crown.
Temperature disparity can also cause damage to the chimney crown. During the winter, exposure to cooler air temperatures causes the crown to become cold. However, when the fireplace is in use the flue can become extremely hot as it vents; the disparity in temperature between the flue and the chimney crown can cause the stone to expand and contract, opening it up to water damage.
Was my chimney crown properly built?
Few homeowners spend a significant amount of time on their roof or looking at their chimney. Therefore, it can be difficult to spot damage or deterioration to the chimney crown. The best way to evaluate the condition of your chimney crown is through a thorough chimney inspection by a certified professional.
When inspecting a chimney crown, the sweep will check to see what material the crown is made of. Concrete, stone, or even metal make up durable chimney crowns. The crown should be a single, solid piece to avoid water seeping into cracks or joints.
The edges of the chimney crown should also extend beyond the sides of the chimney. This overhang, called a kerf, keeps water from flowing directly onto the sides of the chimney. If water damage has begun to occur, a waterproof sealant can be applied to the chimney crown to prevent further damage.
A quality chimney crown can protect and extend the life of your fireplace system. For more information on chimney crowns or to schedule an appointment, contact Jack Pixley Sweeps today.