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Interior Masonry Chimney Clearance

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by lukem, Feb 26, 2013.

  1. lukem

    lukem Minister of Fire

    Joined:
    Jan 12, 2010
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    3,687
    Loc:
    Indiana
    My shop has a masonry chimney (chimney block with clay liner) installed on the inside wall. The existing construction has OSB wall what butt flush with the chimney, as does the ceiling. I'm about to blow in cellulose in the ceiling and it dawned upon me that I might have some clearance issues.

    Is the OSB on the walls or ceiling a concern? If so that's a hard fix.

    Any issue with cellulose in direct contact with the masonry. I can build a barrier to maintain clearance but it is cramped for space and I don't want to mess with it if it's not a concern.

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  2. begreen

    begreen Mooderator Staff Member

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    South Puget Sound, WA
    I don't know code here, but I thought the chimney was supposed to have a 1" (?) clearance from combustibles.
  3. webby3650

    webby3650 Master of Fire

    Joined:
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    Loc:
    southern Indiana
    A 1" clearance is required by code for Masonry chimneys.
    This clearance is rarely met in most houses though. It's rarely an issue, the few times that this was an issue, well, went up in smoke!;)

    I put a liner in a 30" wide chimney that had a flue fire a few days before I got there. Vinyl siding touched the edges of the block flue, and it was all warped and buckled from the heat the entire length of the chimney. It's pretty scary, keep an inch around that chimney!
  4. Pallet Pete

    Pallet Pete Guest

    It varies by county much of the time ours is 2" requirement most of the surrounding are 1". It may be worth calling the stove inspector to find out for sure. Normally it's the mechanical inspectors department you call.

    Pete
  5. lukem

    lukem Minister of Fire

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    Indiana
    Ha! We barely have permits let alone inspectors. If I'm going to honor the 1" I am looking at full tear out because the outsidebwall is completely touching it. I'll pull back some of the OSB on the wall and see if they left a gap in the structure. Judging by the rest of the poor construction I'm guessing not.
    Pallet Pete likes this.
  6. webby3650

    webby3650 Master of Fire

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    southern Indiana
    The 1" clearance is an IIRC and NFPA code. I don't see how a certain county could require more than International codes requires.
  7. Pallet Pete

    Pallet Pete Guest

    I have no idea as to why What is this wood burners against down drafters alliance ? That sounds like its right up my alley lol.

    Pete
  8. webby3650

    webby3650 Master of Fire

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    southern Indiana
    Oh, just professing my deep hatred for down drafters after my experience with a Lopi Leyden.
    Pallet Pete likes this.
  9. Pallet Pete

    Pallet Pete Guest

    Well I might just join you after my Harmon experience lol. Now back to your regularly scheduled thread !

    Pete
  10. tfdchief

    tfdchief Minister of Fire

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    Nov 24, 2009
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    3,332
    Loc:
    Tuscola, IL
    Generally, you need 2 in. clearance to combustibles.

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