The brick chimney sealer is a Silane-Siloxane water repellent sealer. It penetrates into the surface of the brick and mortar where it chemically reacts to form a hydrophobic barrier within the pores. The barrier will reduce water absorption on the surface by up to 95%, therefore reducing damage and deterioration caused by water absorption. Brick chimneys sealed with a water repellent sealer are more resistant to:
Silane-Siloxane sealers differ greatly from a silane sealer or a siloxane sealer. When a silane water repellent sealer or a siloxane water repellent are used independently they aren’t as effective as using a Silane-Siloxane hybrid sealer.
Under the category of Silane-Siloxane sealers there are low solids and high solids sealers, and water and solvent based sealers. Both water and solvent based sealers will offer the same set of benefits when applied to brick, but the percent solids will have an impact on formula.
Low solids solutions, which are typically found in hardware stores, contain 2-8% solids, or 2-8% active materials. This means that only 2-8% of the sealer is Silane Siloxane and the rest is either water or solvent. Professional grade products, like the Armor SX5000 and Armor SX5000 WB contain up to 40% solids, which is considered to be very high when it comes to Silane Siloxane sealers. You get more coverage within the pores and on the surface with a higher solids material. Learn more.
A second type of water repellent sealer is a siliconate water repellent, but siliconate sealers should not be used on brick. Siliconate sealers are known to leave a hardened white residue on the surface when applied to porous or dark concrete or masonry surfaces. Siliconate water repellent sealers can stain the brick with a permanent white residue.
There are a few other things that come into mind when sealing a brick chimney. You want to make sure that the flashing, chimney crown, and chimney cap are in good working condition. You want to make sure that any cracks in the grout are repaired, and you want to make sure the chimney is structurally sounds.