The process of waterproofing a brick chimney involves cleaning all chimney surfaces and making minor repairs before applying a water-repellent sealant. Brick and mortar joints are a common source of leaks that may cause water damage to chimneys and interior environments.
Begin the process of waterproofing a brick chimney by taking accurate measurements to determine how much sealant to use. Clean all surfaces thoroughly using an appropriate cleaner or a power washer to remove mold, dirt, rust and other debris that may interfere with sealant application. Protect all surrounding materials by masking surfaces or laying a drop cloth to ensure the sealant does not cause discoloration or damage. Repair any chimney surfaces that have chipped or cracked or that show signs of wear using a crack and joint sealer.
Allow all surfaces to dry completely before applying the water sealant to ensure moisture does not become trapped between the brick and sealant. Use a pump sprayer with a fan-style nozzle to apply the sealant, beginning with the bottom of the chimney and working upward. Move the sprayer from side to side using slow gradual motions to ensure complete coverage and even application. Adding a second coat of sealant within a few minutes can ensure optimum protection from water and moisture.