chimney leak in rain

How to Fix a Leaking Chimney

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One of the most common maintenance issues with chimneys is leaking during rainy weather. Like all other parts of your home, your chimney will degrade over time due to damage from the sun, rain, and freeze-thaw cycles. Fixing a leaking chimney can range from a simple afternoon’s worth of DIY work to complex repairs. The extent of work required will depend most of the source of the leak.

Diagnosing the Leak: Starting at the Top

Custom Band-Around Chimney Cap

Chimney caps keep rain, birds, and other animals out of your chimney.

If water is coming down your flue (and making an annoying drip-drip noise), you may simply need a chimney cap to keep rain from falling down the chimney. A chimney cap is a metal covering with screen sides and a lid that fits over your flue or flues. The lid keeps rain from falling down the chimney, and the screen sides allow smoke to exit while preventing birds and other animals from getting into the chimney.

  • Prepare. To diagnose your leaking chimney, you’ll need to inspect it from the roof. Make sure you take all the necessary safety precautions when using the ladder and climbing on the roof. If you’re uncomfortable getting on top of your home, call a brick mason or roofer.
  • Inspect the crown. When on the roof, start your inspection at the top of the chimney. Look for cracks, missing pieces, and crumbling concrete on the crown, which is the concrete slab that forms the top of the chimney. Cracks less than 1/4-inch wide can be repaired with CrownCoat, and CrownSeal can repair larger cracks and even missing pieces of the crown. If the crown is so deteriorated that even CrownSeal can’t fix it, you’ll need to contact a brick mason about a replacement crown.

    chimney crown

    The chimney crown is the concrete pad that makes up the top of the chimney. Cracks often form over time that will need repair.

  • Inspect the brick and mortar. Start at the top row of bricks and work your way around and down, looking for cracks in bricks and mortar. Over time the mortar in particular will degrade and crack. Cracks 1/8-inch or less in width can be easily repaired with CrackMagik. For larger cracks, consult a brick mason as you may have structural issues with your chimney.
  • Inspect the flashing. Check around the base of the chimney where it meets the roof for dried up or missing caulking and rusted or out of place flashing. Many flashing repairs can be done with FlashSeal, a heavy duty fiberglass-based sealant that comes with a 7-year warranty. FlashSeal doesn’t require any difficult metal working or messy tar like typical flashing repairs.

    use flash seal to fix chimney flashing

    FlashSeal uses fiberglass and a durable sealant to fix chimney flashing with a 7-year warranty.

Once you’ve addressed all the cracks and flashing problems, consider installing an outside-mount chimney cap. An outside-mount slips over the top of your chimney like the lid of a shoebox, and the large lid overhang keeps water off the crown and sides of your chimney. By keeping water off the brick and mortar, you’ll prevent water damage, saving you from leaking chimneys in the future.

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3 thoughts on “How to Fix a Leaking Chimney

  1. Preeti

    Thank you for the information. I had a chimney work and it did it myself. But after months i am still having leakage on the roof.
    Any Solution for this?

    Reply
    1. Tom Post author

      Sounds like you need to have a roofer take a look. You may have problems that aren’t easily visible around the chimney. Good luck.

      Reply

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