Chimney Crown Sealer is a flexible, waterproof coating that is applied to the tops of chimney crowns to protect chimneys from water damage. This flexible membrane is easy to apply with a paint brush and will last for years. It repairs both mortar and concrete crowns. This durable, elastomeric coating can be used to repair minor cracks in chimney crowns to prevent chimney leaks. A half gallon container will cover approximately 20 square feet, assuming 2 coats.