A crown wash is a masonry coating a-top a brick, block, stone or stucco chimney. It is a vital to have one, intact and functional. What function? Crown washes keep water from entering the chimney to prevent rapid deterioration during the freeze thaw cycles. Crowns and caps with cracks are the first point of water entry in any weather exposed chimney. If your crown is not taken care of and fixed in a timely manner, the cracks can travel down your chimney onto your bricks and cause more costly repairs.