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Waterproofing Your Chimney

In many of my previous articles, I’ve written about leaky chimneys and how to fix them detect leaks and repair them. So I thought that I would talk about how to make sure that your chimney doesn’t leak in the first place. It seems that around this time of the year, after another harsh winter, chimneys have a tendency to leak, deteriorate and in extreme cases, cause fire damage.  It really doesn’t matter if it’s a newer chimney or an older model, but rather on the materials that were used in your chimney’s construction.

Brick chimneys are typically built with materials that absorb water. Whether a chimney was built with clay or cement bricks, bricks act like a sponge.  If the chimney’s mortar joints were incorrectly built, the bricks are more likely to absorb the water, causing it to seep into the interior of the chimney. You would have thought that they could have used a product that would be better suited for rainy weather?

Aside from a stone chimney, all masonry chimney construction materials will deteriorate quickly over time. The freezing/thawing that go on over the winter are other factors that speed up the process. Moisture infiltration further weakens the structure of the chimney rusting out metal, steel and cast iron parts making them vulnerable and wearing them down over time. Some of the parts of a chimney that are at risk include the chimney flue, damper and the flashing.

In any case, many products have been developed specifically for use as waterproofing agents on masonry chimneys. Some of the products use ingredients that allow the chimney to breathe which allows water vapors that have entered the chimneys to escape. They also contain waterproofing agents that prevent water from entering from the outside. Most of these products come with a five- to ten-year warranty. Some people use paint or clear sealers to waterproof their chimneys. And although this might seem like a good idea, these solutions speed up the process because they trap water vapors and moisture inside the chimney causing further deterioration. MasonrySaver All-Purpose Heavy-Duty Water Repellent is a water-based repellant that’s easy to use. For more information, you can check out their website at

Remember that waterproofing prevents water from entering the chimney and shouldn’t be thought of as solution to existing damage or deterioration that already exists in a masonry structure.  If your chimney has already had extensive water damage, it should be repaired before any waterproofing agents are applied. The chimney’s exterior might also have to be cleaned before the application of the waterproofing agent.

American Fireplace Inc. chimney cleaning and residential air duct cleaning services. For more than 20 years, it has served customers in Houston, Texas (TX) and the surrounding areas including Beaumont, Brenham, College Station, Galveston, Katy, Kingwood, Lake Jackson, Woodlands, Richmond, Spring and Sugarland. American Fireplace Inc., We Care about Your Air!

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