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  1. #1
    Join Date
    Jul 2012
    Location
    Indiana
    Posts
    38

    Default Flue gaps at cap

    What is the proper way to seal this gap at the top of a lined chimney on a 1950s house?

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  2. #2
    Join Date
    Mar 2007
    Location
    Lake Barrington, IL
    Posts
    1,363

    Default Re: Flue gaps at cap

    I expect that the gap may be too wide to be effectively sealed. The condition of the flue liner appears to be another issue.

    Eric Barker, ACI
    Lake Barrington, IL

  3. #3
    Join Date
    Feb 2008
    Location
    Chicago IL
    Posts
    1,984

    Default Re: Flue gaps at cap

    you could get by with backer rod and mortar but I would prefer backer rod and solar seal
    some might tell you to use fire caulk but I wouldn't get picky about it at that location
    the key for good life span would be backer rod and a nice sloped joint to promote water run off

    www.aic-chicago.com
    773/844-4AIC
    "The Code is not a ceiling to reach but a floor to work up from"

  4. #4
    Join Date
    Jul 2012
    Location
    Indiana
    Posts
    38

    Default Re: Flue gaps at cap

    Thanks for the replies. Yes, I noted the cracks also and recommended a chimney contractor evaluate the flu more thoroughly.

    I'm not familiar with solar seal...does it have some characteristic over and above silicone caulk? Thanks for the input.


  5. #5
    Join Date
    Nov 2009
    Location
    St Paul, MN
    Posts
    1,628

    Default Re: Flue gaps at cap

    From my past continuing ed courses, that seam should never be mortar but should be backer rod and urethane caulk.

    MinnesotaHomeInspectors.com
    Minnesota Home Inspectors LLC
    ASHI #242887 mnradontesting.com

  6. #6
    Join Date
    Mar 2007
    Location
    Lake Barrington, IL
    Posts
    1,363

    Default Re: Flue gaps at cap

    I though of the backer rod but then you'd be putting a combustible material against the liner.

    Eric Barker, ACI
    Lake Barrington, IL

  7. #7
    Join Date
    Mar 2012
    Location
    Lansdale, PA
    Posts
    876

    Default Re: Flue gaps at cap

    Quote Originally Posted by Kevin Wood View Post
    True but you will hardly ever see it. Anyways that needs a chimney liner as the flue is cracked.
    Even if only the top section is cracked? I have seen that many times. The top section can be replaced if the flue is otherwise ok.


  8. #8
    Join Date
    Mar 2007
    Location
    Near Philly, Pa.
    Posts
    1,643

    Default Re: Flue gaps at cap

    The codes have never figured this one out. Things that do well against heat don't do well keeping out water and vice versa. I have used fiberglass rope gasketing with red RTV silicone on gaps up to about 1/4". Gaps wider than that should trigger a crown rebuild. The codes only recognize carrying the flue tile up before the surrounding wythes. Yes, you 'can' butter the joint, lower a tile, strike the joint on the side and call it a day. Not what the code allows but it is a practical repair IF it is only that one tile. However, this should trigger a Level II and I seriously doubt a proper inspection would reveal the rest of this chimney does not warrant a liner. Whether this damage was from a water penetration, a chimney fire, mis-handling at construction or whatever, we know it needs to be replaced, we need to perform a level II and most likely, there will be evidence of significant water penetration and damage below. You can make chimneys with simply crummy mortar crown washes or you can go for the gusto with a bond break under a concrete crown with a drip edge or even do a full sheet lead through-pan with weep holes like they do in the UK.

    Keep the fire in the fireplace.

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