The Wash Crown is the top cement portion that seals off the upper opening of the chimney. The Wash Crown is a very vital part of the chimney where damage often occurs, and spreads down the rest of the chimney continuing to cause more damage. The majority of masons use a half-inch of masonry mortar to install their crowns.
Standard mortar is weak and has no flexibility. During the winter, snow sits on the crown, but when it thaws, the water gets absorbed into the masonry. As the water freezes and expands within the masonry it eventually cracks the crown. When the Wash Crown is cracked, it leaves the chimney extremely vulnerable to water penetration. Eventually this water leads down the chimney and into the house. As the water works its way down the chimney, it continuously freezes and expands within the bricks causing further structural damage. This damage includes vertical structural cracks, loosening of bricks from the mortar, deterioration of mortar joins and the spalling of bricks.
Sposato Masonry has different methods of repairing and replacing crowns to avoid these issues. We use high psi cements in addition to additives that increase freeze-thaw durability and flexibility. We also use reinforcements in our crown mixes as well, which mimic steel reinforcement used in load-bearing concrete.