Chimney Tops
The chimney top (also referred to as the chimney crown, wash cap, or splay) is the top element of a masonry chimney. It covers and seals the top of the chimney from the flue liner to the chimney edge. The concrete crown should provide a downward slope that will direct the water away from the flue toward the edge of the crown. A properly constructed crown will have an overhang at the top edge of the chimney and have a drip edge, this will direct the run-off from the crown away from the chimney and help prevent erosion of the brick and mortar in the chimney’s vertical surfaces (sides).
A properly constructed crown is your chimney's best protection from the elements of weather and will help prevent damage further down the chimney that could be very costly to repair.
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Most masonry chimneys are built with an inadequate crown constructed from common mortar mix that will crack, chip, or deteriorate from weather exposure. A proper chimney crown should be constructed of a Portland cement-based mixture and cast or formed so it provides an overhanging edge projecting beyond all sides of the chimney by a minimum of two inches. A crown may also be composed of stone or metal over a brick overhang.
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The flue liner tile should project above the crown a minimum of two inches. There must be an expansion joint around each of the flue tiles (see chimney flues and liners for more info.).
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A masonry crown should have a bond breaker between the crown and the masonry material (brick, block, stone, or mortar joints) that are supporting the crown. This break in the bond is important to protect the chimney below the crown. If the crown should develop a crack, this break in the bond will help prevent the crack from continuing down into the chimney below.
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A properly constructed crown is your chimney's best protection from the elements of weather and will help prevent damage further down the chimney that could be very costly to repair. Damage to the crown itself does not prevent the chimney from being used for its intended purpose but if this area is not repaired subsequent damage could occur that could affect other parts of the chimney and could interfere with its intended function.
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