Q&A Waterproofing a Chimney

QandA Posted By QandA, Oct 5, 2001 at 2:20 PM

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  1. QandA

    New Member 2.
    Staff Member

    Nov 27, 2012

    About a year I moved into a house with a Federal Airtight wood stove insert. The last rain storm (about 10 in. over 48 hours- in October 96) caused a substantial amount of water to leak into our room at the base of the stove near the fireplace. This never happened before. Although we never got this much rain before- it started leaking when we only had about three inches. Last spring and about 1 month ago we had storms that dumped about 4" of rain and nothing happened. Curiously- there isn't much water in the cleanout in the basement. I was advised to put a venting cap on the chimney to keep out the rain- as well as leaves and animals. Will this do it? It seems to me that something is leaking and shouldn't be. Could leaves have blocked the passageway that leads water to the cleanout?


    There are a few causes and solutions:
    1. A cap on the chimney will help to avoid certain water problems.
    2. The flashing where the fireplace joins the chimney should be checked. Water leaking in here can end up in the firebox.
    3. The masonry on the outside of a chimney can become porous- allowing lots of water to soak thru and end up in the firebox. Use some masonry waterproofing liquid (brush or spray on) to solve this one.
    4. The crown- or top of the chimney can become cracked and allow water through. Patch and waterproof..the cap helps with this one also.
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