Chimney Waterproofing – Can Water Damage Really Destroy Your Masonry Chimney?

Here in Cincinnati, I’m sure I don’t speak for myself when I say I have a new respect for hurricanes. We recently experienced hurricane force winds that caused more damage to chimneys than this city has seen in a while. When someone thinks of a hurricane, lots of water comes to mind, and when it comes to chimneys, few things are more detrimental to its life and quality than water damage. Not to mention there are few things more aggravating than the drip, drip, drip of water entering the chimney, resonating through your home and eventually through your very soul… Well, it may not be that annoying but no one wants to have to write a check for a major chimney overhaul due to moisture damage when it is easily preventable.

Water Damage: A $1 Billion Per Year Problem

This damage comes in the form of staining, loss of insulation value, freeze-thaw damage, deterioration, and ultimately, structural failure. In light of this, I’d like to discuss a few systems, products, and techniques to ensure your family is safe, warm, and dry this hurricane or winter season, whichever you are preparing for.

Masonry chimneys are more prone to water damage than the rest of your home because they extend far above the roofline, unprotected from the elements. Waterproofing is a good idea because it protects the mortar joints from moisture entry and helps a repair last longer.

Waterproofing and Sealers

chimneysaver-buynowAs far as waterproofing goes, Chimneysaver© is the product we use out in the field. It’s important to know the difference between waterproofers and sealers. ChimneySaver is not a sealer. Sealers and silicone coatings form a water resistant surface film which traps water vapors. If these vapors cannot escape, they will add to the deterioration of your brick. Your chimney needs to breathe, which is why we use Chimneysaver©. It’s 100% breathable, or vapor permeable, meaning water vapor trapped inside the brick can easily pass through it. This is a non film-forming water repellent that will penetrate and line masonry pores to prevent water from deteriorating the brick.

Mortar Joint Repair

crackmagik-buynowBefore you waterproof, make sure all the mortar joints are in good condition. If there’s any cracks or missing pieces of mortar, you may need to do some tuckpointing. If the cracks aren’t severe, you may be able to apply a brushable product called Crack & Joint Sealant. Think of it like a brushable caulk that dries semi-clear. This waterproofs the gaps and cracks in the mortar up to 1/8″.

Waterproofing your masonry chimney can preserve your chimney and prevent water damage and deterioration. A good water repellent normally only needs to be applied once every 5-10 years and will save you the headache of having to replace or rebuild your chimney.

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18 comments on “Chimney Waterproofing – Can Water Damage Really Destroy Your Masonry Chimney?

  1. Cynthia on said:

    I think it is better to call someone to have it repaired. The things mentioned by granite sealer are important as well but for immediate solution only I guess.

  2. barbbi on said:

    I have a beautiful fireplace in my back room. However, when it rains the water comes running down the front of my bricks, and onto the hearth, where it makes it way to the carpet.
    I just had a new roof put on, thinking that was the problem, wrong. It happened again. Then I had a mason come and put a sealant on and fix any visible cracks, didn’t help. It rained yesterday and it happened again………….Any comments? I need help!!!!!!!!!!

  3. admin on said:

    Water normally comes in through 1 of 3 sources, the crown, the flashing, or through the bricks and mortar joints. It’s important to use a breathable water repellent rather than a film forming sealer on chimneys as they need to breathe. I would be looking closely at the flashing. Sometimes even with new roofs, the flashings are not constructed properly. There’s a product called FlashSeal that you may look into that you can coat around the entire flashing and prevent water penetration.

  4. chimneyadmin on said:

    Barbbi,

    I would suggest doing a water test. Start by saturating the brick at the lowest possible point of water entry. Wait 20 minutes. If no water is entering, try saturating a little higher up until you can pinpoint where the water is entering.

  5. Shelly on said:

    Remodeling a bathroom- Exposing the corner of the old chimney, which I want to leave, How do I seal to keep the natural look of the brick. Its very sandy and dry? Thanks

  6. Marie on said:

    We just had waterproofing applied last week. It rained less than 24 hours later. Will that effect the ability of the waterproofing to do its job?

  7. Pingback: Chimney Flashing Repair Guide | Ask The Chimney Sweep

  8. chimneyadmin on said:

    Rick,

    This is a great question, because most people think they have to apply the CrackMagik first, however this is not the case. You apply ChimneySaver water repellent first. There are two different water repellents that are offered.

    One is water based and the other is a solvent based. If you use the water based ChimneySaver you can apply the Crackmagik immediately following while it is still damp. If you use to solvent based ChimneySaver, you must allow it to dry completely before applying Crackmagik.

    If you click here you can watch a video on how to use Crackmagik.

  9. I recently had my chimney waterproofed (as well as repairing the flashing and top cap). But I was not home and my wife said they were done in 30 minutes. Now it is better but still leaking. How can I tell if they actualy applied the sealer? I notice a white residue in the cracks but only at the top of the chimney?

  10. chimneyadmin on said:

    My first suggestion would be to contact the contractor who performed the work, if you have not done so already. This is important because they can walk you through the process of the job they performed. Please keep in mind, when dealing with water problems it is always a process of elimination. I cannot give an answer in regards to the time it took or what the white residue is, because there are many things that factor how much time a job takes. Again this is why it is important to call your contractor and have them explain in detail what they did. As far as being able to tell if they waterproofed the chimney, the best way to think of it is like car wax. When you put wax on your car and it rains the water will bead, this is the same thing when you waterproof your chimney. If you spray the chimney with water and it has been waterproofed, you should see it bead. If you are still noticing a leak it could be coming from a different area, again, this is why water problems are process of elimination. Contact your Contractor and have them come by and take another look, and help you understand what they did. Don’t be afraid to ask questions!!! Also take a look through the site at some of the videos we have showing the process of waterproofing.

  11. A leaky chimney can do thousands of dollars in destruction to your home or business in the form of insulation saturation, drywall warping, unsightly wall & ceiling stains, mold growth and floor covering damage. Loose mortar joints, damaged brick, foundation cracks, or flashing that appears to be in disrepair should all be addressed immediately.

  12. Most often than not the problem is with flashings around the chimney and not the brick. But as with every exposed material, wear and tear damage is a reality. Just like with pavement, sealing is the only real prevention solution.

  13. Karl on said:

    When waterproofing my brick, does the whole chimney need waterproofed or just the part that extends past the roof line?

  14. All masonry material-surfaces are pours!
    Including the chimney top crown their are 5 side of chimney.
    I personally believe all masonry need to be protected with a
    higher end “penetrating” water repellent.
    ( not the much less expensive “film covering” products
    I also prefer doing light or fogging “wet on wet” applications much
    better then just soaking the chimney masonry and watching run off of the roof top
    Regards
    clay
    Waterproofing Chimneys:
    http://youtu.be/hSY4ApHXLl4
    Chimney Leaks:
    http://youtu.be/hNU-W7YmI5E

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