Base of chimney mortar dryrot

Post in 'DIY and General non-hearth advice' started by Uncle, Dec 26, 2012.

  1. Uncle

    Uncle
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    Hi everyone and Happy Holidays...

    The mortar on the base of my chimney has dryroted to the point that I have a piece of brick missing. Much of the mortar can be removed just by scraping with a screwdriver.

    At this point I don't think it's a DIY project I would feel comfortable doing on my own. I would like to know if anyone has had a simular situation and what they did and how much it cost (ball park).

    The chimney base is on a cement floor, it is used for my oil burning boiler and has a stainless liner in it now.
     

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  2. ScotO

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    some pictures would really help us see what is going on. Re-pointing is all about preparation......getting the old mortar out is the most important thing. I'd be digging out at least 1 1/2" to 2" of that mortar, and making sure you have the bricks cleaned off where the old mortar was on them. Using a tuckpointing bag (grout bag) and a pointing tool, it wouldn't be a hard job at all if you have some basic masonry skills. Just make sure you use a good cement (either a type "S" or type "N", or a Portland mix mortar), and take your time, it'll be as good as new.
     
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  3. chimneylinerjames

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    Well since it isn't just the mortar, the brick also that is falling apart, I would recommend something else. When I have encountered this situation I encased the chimney in concrete. Build a form around the chimney, leaving what you think is good/have room for, maybe 4" on all sides of the chimney. Use some re-bar, drill some holes into the floor and have stakes straight up. Clean up the loose masonry with a wire brush. I have done this a few times for customers and it works great. Definitely a project you could under take.

    The reason this could have happened is the moisture from inside the chimney was dripping down and collecting on the bottom. Make sure your new liner has a cap on the end of the tee.
     
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  4. Hogwildz

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    If it is just one or two bricks missing, get a competent mason to look at it and see if it can be repointed.
    Make sure he checks and makes sure the stone top cap is tight also.
    If this is throughout the entire chimney, sounds more like the mortar originally used was not prepared properly, or was subpar materials.
     
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  5. Uncle

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    I forgot to mention this is a very old house (200 years) but I don't know how old the chimney is. The previous owners did extensive work on the foundation but as far as the chimney the only thing I noticed was some raised cement around the bottom. Also it is an indoor chimney. The part above the roof line is in excellent condition.

    If I were to build a form and cement it what diameter of rebar should be used? Also how deep should the holes be drilled for the rebar?
     
  6. jdp1152

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    Take some pictures. I redid a few bricks in mine without much work. You can buy fireplace mortar premixed and use a caulk gun to apply it. There is a this old house video out there somewhere detailing this.
     
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  7. chimneylinerjames

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    Use whatever rebar you have or have a concrete bit for. 1/2" is fine. I would say drill down maybe 2" into the floor.
     
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