Lindemann CrownSeal - 2 Gallon Long Lasting, Exterior Waterproof Membrane for Chimney Crowns, Chimney Corbels & More! Natural Concrete/Mortar Look & Permanently Flexible No Bonding Agent Required & Ready To Use Coverage: 1/8" Thickness = 14 - 18 Square Feet Per Gallon; 1/4" Thickness = 7 - 9 Square Feet Per Gallon