We often get asked what is the difference between a chimney crown and a chimney chase cover, and how do I know which one I have?
A chimney crown, or wash, is the mortar or concrete portion of the chimney located on the outside top of the chimney that covers and seals off the airspace between the outer brick walls of the chimney and the flue liner, and assists in shedding water away from the chimney. It can take the form of a sloped bed or a rectangular "formed & poured" shape. Standard masonry chimneys are topped by mortar crowns.
A chase cover is the top portion of the chimney that covers the chimney chase, which is the commonly used term for a wood framed chimney. A chase cover serves the same purposes on a chimney chase as the mortar crown does on a masonry chimney-- airspace sealing and water protection, but it is usually made of either galvanized sheet metal or stainless steel. Factory built, or prefabricated chimneys, are topped by chase covers rather than masonry crowns.
Both crowns and chase covers will deteriorate over time due to their open exposure to the elements, especially water. Concrete crowns will develop cracks in the concrete and metal
chase covers will rust and corrode over time. Both kinds of deterioration can lead to water damage to the interior components of the chimney and fireplace. Crowns and chase covers can be repaired easily if the damage is caught early.
