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Thread: Multiple flues

  1. #1
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    Default Multiple flues

    According to NFPA 7.2.14, a 4 inch seperation is necessary between flues. My question is this; notwithstanding this standard, I've read that two flues can be installed in the same chimney so long as they maintain a 4" clranance at the top and "taper" toward the bottom. Anyone else hear of this before?

    NFPA 211
    Standard for
    Chimneys, Fireplaces, Vents, and Solid Fuel-Burning Appliances
    2006 Edition
    7.2.14.1 Where a chimney contains more than one flue, a separation shall be provided between adjacent flues.
    7.2.14.2 The separation shall be of solid masonry wythes (partitions) constructed according to one of the following:
    (1) Not less than 4 in. (102 mm), nominal, in thickness
    (2) Of reinforced portland or refractory cement concrete not less than 4 in. (102 mm), actual, in thickness
    7.2.14.2.1 The partitions shall be bonded or securely tied to the chimney walls.

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  2. #2
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    Default Re: Multiple flues

    My guess would be that what you cite would not apply to a 40 year old installation or old dense clay tile. Since I don't work in CA, just guessing based on what's normal around here.
    I come across those installations on larger homes. The biggest problems I encounter are shifting of sections, and bird or squirrel entry. I recommend full inspection to check the joints for shifting, mortar erosion in the basement from years of water entry and critter guards.

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  3. #3
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    Default Re: Multiple flues

    Quote Originally Posted by Markus Keller View Post
    My guess would be that what you cite would not apply to a 40 year old installation or old dense clay tile. Since I don't work in CA, just guessing based on what's normal around here.
    I come across those installations on larger homes. The biggest problems I encounter are shifting of sections, and bird or squirrel entry. I recommend full inspection to check the joints for shifting, mortar erosion in the basement from years of water entry and critter guards.
    Yea, that's a good point.It's a late 70's home so I guess I need to see what code was back when.

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  4. #4
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    Cool Re: Multiple flues

    The 4" wythe wall applies to separate appliances. You can have twin side by side flues serving a fireplace, much like a double barreled shotgun as long as the flue tiles are properly supported 360* at the base, grouted btw the tiles at the center, and stagger their joints as they carry up. Thus, if you grouted the gaps btw the tiles at the base and have adequate support around the perimeter, then this chimney would appear acceptable based upon the limited info. presented.

    I believe Ca. would have been under the UBC back then but why do you need to conduct a forensic investigation? Not necessary unless part of litigation or an open case.
    HTH,

    Keep the fire in the fireplace.

  5. #5
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    Default Re: Multiple flues

    Quote Originally Posted by Bob Harper View Post
    The 4" wythe wall applies to separate appliances. You can have twin side by side flues serving a fireplace, much like a double barreled shotgun as long as the flue tiles are properly supported 360* at the base, grouted btw the tiles at the center, and stagger their joints as they carry up. Thus, if you grouted the gaps btw the tiles at the base and have adequate support around the perimeter, then this chimney would appear acceptable based upon the limited info. presented.

    I believe Ca. would have been under the UBC back then but why do you need to conduct a forensic investigation? Not necessary unless part of litigation or an open case.
    HTH,
    Thank you Bob. The agent was just asking about the code at the time of original construction.
    Is that wood installed in accordance to minimum building standards?

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  6. #6
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    Default Re: Multiple flues

    Hi Guys,
    I know Im new here and have been reading for months without posting. As a chimney/fireplace inspector. Heres what I see.
    the first set of pictures Id be concered with the offset of the tiles. The refractory cement is gone and I can see throu the tile joint.
    The second set of pictures shown with the wood. Is that a smoke chamber?
    Thats just what I see from a csia stand point, but like I said Im just a newbie to the board.
    Jeremy

    Last edited by jeremy larson; 10-11-2010 at 12:13 PM.

  7. #7
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    Default Re: Multiple flues

    Welcome Jeremy, to the site.
    Yes that is wood at the breast plate. I am also concerned about the flue joints. Dale Feb is going out there tomorrow for the buyer so we'll see what he comes up with.

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