Just as your house needs a roof to keep water from entering, so does your chimney. Chimney crowns are simply the mortar “roofs” of masonry chimney systems. Poor crown construction is a leading cause of chimney deterioration due to the entry of water into the system through the faulty crown. Water entry into a masonry chimney causes freeze-thaw erosion, mortar deterioration, spalling (flaking), and efflorescence (mineral deposits on the surface of brick), and will eventually destroy the chimney.
Like the sloping roof of a house, the chimney crown should slope down from the flue liner. Flat crowns or those with minimal slope can allow water to enter the interior of the chimney. Crowns should be poured at least two inches thick at their thinnest point. Thin crowns do not have as much resistance to water as a properly poured crown and tend to wear away and crack much faster, allowing water entry. A chimney crown should extend a minimum of 2 and 1/2 inches beyond the face of the chimney on all sides. This overhang helps to keep water from running down the chimney face.
If your crown has deteriorated, Barnhill Chimney can repair it. If it has only minor cracks and is otherwise in good shape, we may just recommend you install a full size chimney cap to protect it from further weather-related wear and tear. If it has a lot of cracks or is a little chipped around the edges, we can seal it. Sealing the crown restores its original water resistant state and can greatly prolong the life of your chimney.
Our product of choice, CrownCoat, is a premixed, trowel grade, elastomeric coating that forms a flexible waterproof membrane to protect chimney crowns and more. It cures in about 24 hours to a natural concrete/mortar appearance. It is used on chimney corbels, the tops of masonry and parapet walls, or wherever a flexible waterproof membrane is needed. CrownCoat can be colored using standard mortar dye.
We do not use tar to seal any part of the chimney. Tar does not expand and contract along with the chimney, so it tends to crack and fall away very quickly, often within only a year or so. CrownCoat (and related products) are designed for use on chimneys and can last many years.
If your crown looks like some of the photos above, or has worn away completely, we may have to build a new crown. Our chimney crowns are constructed using cast-in-place reinforced concrete. They are built a minimum of four inches in thickness. We use industry- and application-appropriate materials, and take care to protect your roof during installation.