How to Seal a Chimney

One of the most problematic areas of a home is the chimney. Water and moisture can cause scaling, deterioration, spalling, water intrusion in the home, and freeze/thaw damage. Waterproofing and sealing a chimney can be vital to its structural integrity.

Before sealing a brick chimney, clean the surface with a brick cleaner to remove all curing compounds or visible stains such as mold, mildew, efflorescence, or rust. The chimney should be clean and free of dirt, oil, dust and any unwanted contaminants. For severe mold, mildew, fungus, or algae use a bleach solution.

When dealing with a chimney, it is important to practice safety and never get on a ladder or roof without the proper knowledge and experience. Wear chemical resistant gloves and safety glasses when handling cleaning solutions.

Protect surrounding plants and shrubbery with a tarp or plastic cover. Apply the cleaning solution with a brush, garden sprayer, or pressure washer. Allow the cleaner to dwell for a few minutes on the surface. Use a scrub brush or pressure washer to wash the brick thoroughly, starting at the top and working down. Be careful not to use excessive pressure when using a pressure washer or you can damage the mortar joints. Rinse well with fresh clean water and allow the surface to dry completely. Additional heat can be applied to facilitate sufficient drying time.

Apply a brick and chimney sealer evenly using a siphon pump, bulk sprayer, or pump-up sprayer. Follow the manufacturer’s coverage guidelines to determine the amount of sealer for the project. The coverage rates will vary slightly depending on the type of brick and porosity. Soak the surface well to ensure complete saturation. When using a sprayer, follow up with a brush or roller to even out the sealer and reduce excess that may cause runs and drips. Once the entire chimney is sealed, allow the proper drying time as directed by the manufacturer.

Learning how to seal a chimney is not hard if you follow these simple guidelines and all the manufacturer’s guidelines on the cleaning solutions and chimney sealers. Protecting your brick chimney is certainly a money saving investment. A quality chimney sealant will provide years of protection from deterioration, water damage, and premature costly repairs.

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