CrownSeal by ChimneySaver is a flexible waterproof coating for your masonry chimney crown that is used to seal deteriorating chimney crowns and fill cracks and defects. Dries to a natural concrete look. 1-gallon cover approx. 18 sq. ft. ) at 1/8" thickness). Dries in six to eight hours. Cures completely in 24-72 hours.