What is Crown?
The poured concrete or stone slab that caps the top course of a masonry chimney, and not the same thing as the metal chimney cap. Its job is to shed water off to the sides, away from the masonry underneath. Let cracks form and water seeps into the brick, which speeds up freeze-thaw spalling. Hairline cracks take a crown coat sealing; serious damage means a full rebuild.
Related terms:Chimney CapSpallingCrownCoat