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Knock down an old chimney below roof height, or re-flash/fix?

Kevin Neijstrom | Posted in Energy Efficiency and Durability on

I have an old, second chimney on my 1881 2-family that is leaking water due to a terrible flashing job. It’s only used to vent the plumbing stack (I think). We believe that originally it was used for a kitchen wood stove.

I received quotes to re-flash it (>$1,000 for copper), but after reading some articles here (Martin’s “Farewell to the Chimney”, etc.) I’m thinking that I should knock it down below roof height and just vent the plumbing stack through the roof. This would prevent tough-to-seal air leaks, as well as conduction loss through the roof. I plan to seal up and later super-insulate the house. I’m afraid if I re-flash it now, I’ll want to just knock it down below the roof height later on to improve air sealing, thus wasting $1000+.

Any thoughts? I live in Zone 5A (West Concord, MA).

Thanks – I appreciate any input,

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  1. David Meiland | | #1

    I got rid of two just like that on my house.

  2. GBA Editor
    Martin Holladay | | #2

    A job like the one you are describing is done all the time. As you remodel each floor, you can keep demolishing your chimney, one story at a time, gaining interior space with each brick removed. You might end up with a linen closet or a broom closet where you chimney used to be.

    One aspect of your question makes me nervous, however. You wrote, "It's only used to vent the plumbing stack (I think)." You need to verify the parenthetical doubt there! You must be absolutely sure that you know how every combustion appliance in your home is being vented -- and you need to be sure you understand what is connected to this chimney -- before demolition begins.

  3. Robert Post S.E. Pennsylvania Zone 4a | | #3


    It sound like you do not have combustion equipment venting through the chimney. Obviously, it is important to be clear about how all combustion appliances vent.

    When the opportunity presents to remove a chimney, it is a good time to consider upgrading to condensing combustion appliances: they run at 95+% efficiency and require no roof penetrations if vented directly through the side of house through PVC.

    I recently did a project where we upgraded the HWH to a 95%er (the last thing vented through the chimney), removed the chimney, re-roofed with 3.5" exterior foam, and dense packed cellulose to rafter bays for a r-50 roof assembly.

    As Martin indicated, an added benefit was increased closet space on the 2nd fl. and room for a built-in on the first floor.

    As you mentioned, Air-sealing will be easier and you'll break that connection between the basement and attic.

    Good luck!

  4. Kevin Neijstrom | | #4

    Thanks for the answers so far! It sounds like I should demolish it.

    To answer Martin's concerns, I'm 100% sure that no combustion appliances are venting through the chimney. We only have one (aside from gas stoves), a boiler, and that vents through the other, main, chimney. The HWH is indirect. There's one PVC pipe that enters the chimney in the attic, and it comes from the space right above a bathroom, so I'm pretty sure that it's the plumbing stack/DWV. Good advice to verify this first -- I will do that.

  5. David Meiland | | #5

    There was an interesting (horrifying) thread elsewhere about a chimney that had been demo'd below the roof and left standing in the attic. There were one or two gas appliances using it in the basement, but the person who did the demo (a roofer?) never bothered to check.

  6. Matthew Amann | | #6


  7. David Fay | | #7

    I just demolished an unused chimney in my 1850's Greek Revival cape in Maine for similar reasons. Here are couple of thoughts:
    1. Historic preservation is probably a dirty word around here, but a chimney can be an important part of the exterior look of an historic house. If you live in a historic district, you may have trouble getting approval for demolishing a chimney. For my house, as originally built, there were two symmetrical chimneys with somewhat fancy brickwork. One had been removed long ago, so I didn't have too many qualms about removing the other. Nor was it in a historic district. But think carefully about the way your house will look before tearing down that chimney.

    2. You'll need to find a way to air-seal the top of the chimney stump. I used plywood as a cap with a lot of spray foam to make it airtight. Without sealing it, you're keeping a stack into your attic, if not to the outside.

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