How much does it cost to water seal a chimney?

The cost to water seal a chimney typically ranges from $150 to $450, depending on the size of the chimney, its accessibility, the height of the roof, and the specific type of waterproofing product used. Professional chimney sweeps and masons generally use vapor-permeable water repellent sealants rather than standard waterproof paints, as breathable sealants prevent liquid water from penetrating the brick while still allowing trapped interior moisture to escape without causing spalling. If minor tuckpointing or minor masonry repairs must be completed before the sealant is applied, the total project cost may increase to between $400 and $800. While hiring a professional ensures even application and coverage, homeowners who are comfortable working on roofs can purchase a gallon of commercial-grade siloxane or silane masonry water repellent for $40 to $100 and apply it themselves using a standard garden sprayer or roller.