Decommissioning a flue

Discussion in 'HVAC Heating & Cooling' started by Dana, Dec 4, 2009.

  1. Dana

    Dana In the trades

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    My newer gas fired heat/hot water system is side vented, and I've been pondering what's the best/right/legal option for decommissioning the flue.

    This is a circa 1923 red brick chimney with two separate terra cotta lined flues, one for a (not-much-used but functional) wood burning fireplace, the other formerly used for a gas fired boiler & hot water heater, the latter of which is now not use. It's an air infiltration source, and it leaks a tiny bit rainwater into the basement in super-downpours, so I'm thinkin' I should probably do something with it at some point...

    Can I just brick it up at the bottom and cap it a the top? (Plan-A)

    Do I need to/want to fblow it full of rock wool (at least up to the roof line), since it's on an exterior wall, then brick & cap it? (Plan-B)

    Should I just cap it & fuggedaboutit? (Plan-C)

    Or should I do something else?
  2. Ian Gills

    Ian Gills Senior Robin Hood Guy

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    I would always install a chimney cap on any chimney.
  3. hj

    hj Moderator & Master Plumber Staff Member

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    chimney

    Put a chimney cap on them to keep the rainwater out, then seal the openings into them to prevent drafts.
  4. Dana

    Dana In the trades

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    However, in this case I'm talking about a ceramic or cement-board cap that seals it at the top, not just a rain-hat for the flue to keep the drips out...
  5. burleymike

    burleymike New Member

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    Location:
    Idaho
    If the masonry is in good shape you can just get some galvanized flashing and use silicone to glue it over the top of the liner opening. That way no more air/water will enter and it will keep cats out. You can seal it up the same way in the basement. You should have the flashing hang over the sides of the liner 1/4"-1/2" to direct water away from the liner.

    That is what I did on mine. I plan to use that chimney in the future for a wood stove. It is in super good shape for being 50 years old. The liner still looks new. I actually found a barn cat in the basement. There was some hair stuck around the chimney opening, so I knew that was how he got in.
    Last edited: Dec 7, 2009
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