5 Myths about Waterproofing Chimneys

Chimneys can take a beating from severe weather year round — and water penetration is the greatest cause of deterioration and damage. According to the Chimney Safety Institute of America (CSIA), all masonry chimney construction materials — with the exception of stone — will suffer “accelerated deterioration as a result of prolonged contact with water.” We’re not just talking about rain, either; snow, sleet — any type of moisture, really — can do a number on your chimney over time. However, waterproofing your chimney extends the life of your chimney for years to come and will protect it against costly chimney repairs down the road. 


While the notion of a waterproof chimney sounds appealing enough, not all homeowners are on the same page regarding why it should be done, what it entails, and the structural integrity of their chimney in general. Let’s bust some of these top chimney myths!

Myth #1: Bricks should not be waterproofed because they need to breathe

Fact: Bricks are porous and do need to breathe. That’s why it is important to use a product specifically designed for chimneys and exterior masonry. At Chimney Heroes, we use a unique repellent that is vapor permeable so it will not trap water vapors in the brick. Water repellents that trap the vapors in the brick actually cause spalling rather than preventing it. As some of the best chimney water repellent out there, it is proven to reduce water penetration by 99.9%! If you own a Van Patten home in Clifton Park with a beautiful brick or masonry chimney, this is the perfect application to avoid future expensive repairs.

Myth #2: Water cannot get into my chimney because I have a chimney cap

Fact: Chimney caps act like rain hats. If you only wore a hat in the rain, it would keep your head dry, but the rest of your body would be soaked. It’s far better to wear rain gear head to toe if you must be in a storm. Your chimney however does not have a choice. It faces every storm, and the majority of them are unequipped for the fight! Did you know that nearly every chimney you encounter has signs of water damage? Brick chimneys absorb water like a sponge. Oftentimes, leaks in attics and walls against a chimney are simply from the bricks absorbing the water from the rain, and then shedding the water below the roof line. The well-defended chimney has a good screened stainless or copper chimney cap, a sealed top crown, vapor permeable waterproofing application, and proper flashing. Is your chimney equipped?


Myth #3: My chimney has held up for many years, there is no reason to do it now

Fact: We hear this a lot in older and beautiful neighborhoods like Saratoga Springs, Niskayuna, and Ballston Spa. Bricks are made to be a strong building material. However, just like pressure treated wood, the weather will always win if not properly maintained. If your chimney is over 10 years old, chances are it has already suffered water damage that you cannot see from the ground. Small cracks will form that you can only see up close. Water will enter these small cracks and when freezing temperatures come the cracks will enlarge. 9 out of 10 masonry chimneys already have cracks at the top of the chimney. The question is, do you want to spend a little now to prevent further damage, or budget to rebuild the whole thing once you can finally notice the damage from the ground?

Myth #4: The bricks don’t matter because my chimney is lined

Fact: It is important to take care of your appliance and to have it vented safely and properly. Even if the appliance is lined or no longer venting into the masonry bricks, the bricks are the outer support structure and serve as part of the liner system. It is important to take care of the structure around the chimney liner. Water can still leak in between the liner and deteriorate from the freeze-thaw period and erosion over time. The liner is a critically important part, and no chimney should be used without one. The moisture alone from the elements of combustion venting through an unlined or damaged liner would wreak havoc on the inside of the masonry chimney walls causing efflorescence and general weakening of the bricks.

Myth #5: My chimney is in good condition because it looks good on the outside

If it looks good, waterproofing will keep it this way. Maybe you think it looks good but you have noticed some white areas or moss growth. The white is called efflorescence and is a sign of water issues. Moss also grows where water sits in the chimney and the plant has found a place to root itself. Even if you do not see white or moss, water only needs a hairline crack to creep into! Once water penetrates, the damage expands with time.

Chimney Waterproofing: Frequently Asked Questions

We’ve put together some common questions we get asked about chimney waterproofing:

How long does chimney waterproofing last?

Chimney waterproof coating will wear down over time, gradually losing its effectiveness. For optimum performance, chimney waterproofing should be professionally re-applied every five years. A certified chimney specialist can give you a more specific answer depending on the state of your chimney and local climate.

Should you paint your exterior chimney?

Painting exterior brick traps moisture inside of the masonry, and as seasons change, this moisture expands and contracts. This can damage bricks as well as any paint that covers them. While painting a chimney to stop water from entering may sound good in theory, certified chimney sweeps and masons do not recommend it.

Should I use my own chimney sealer?

While applying chimney sealer seems like a straightforward enough job you can do on a free afternoon, it’s a much more involved project — and one you should leave to the professionals. Your chimney is a complex system, and only a trained eye can accurately assess the current state of your chimney and shed light as to what may come if you don’t take action — most notably, damage you didn’t even know was in the pipeline. All in all, when you’re looking to waterproof your chimney, get in touch with a pro!

Turn to Chimney Heroes for Comprehensive Chimney Services Today

Chimney masonry repair and waterproofing should be done in the spring and summer. When temperatures drop below 40 degrees it becomes very difficult for the material to set properly.  For more information about the importance of waterproofing your chimney or any of our offerings — including chimney inspections — contact Chimney Heroes today. There is still time to take care of your bricks and mortar before the damage spreads!