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NG Insert - Outside of Firebox

Post in 'It's a Gas!' started by nate5280, May 12, 2013.

  1. nate5280

    nate5280 New Member

    Joined:
    May 12, 2013
    Messages:
    2
    Loc:
    Denver
    I can not find good guidance on this issue, so was hoping for help.

    I am going to add a direct vent insert to an existing fireplace, not planning on a blower because it is for one small room. I can just mount it normal, but I would really like to purchase an antique wood surround and mantel I have found that would make this project a bit more complex. This surround extends about 10 inches in front of the wall that the existing fireplace is installed in, resulting in a dead space between the antique wood surround and the existing tile surround for the fireplace. So, in order to mount an insert flush with the face of the antique surround, the insert would have to extend 10" out of the firebox.

    Note that the insert would not be directly against the wood surround, I would have about 15" on top and 10" on each side for a nonflammable surround, and plenty of clearance for the mantle.

    My question is: The manuals I have read for inserts do state that the insert should be in an existing fireplace. However, is this 10" extrusion going to really be an issue, either with safety or damage to the wood surround? If so, any ideas on a cheaper solution, if i need to have a full masonry extension added to the existing firebox, I will probably skip this plan, but if some cheaper/easier insulation in the 10" dead-space would work, that would be great. I have thought about using a zero clearance fireplace, but with the existing dimensions of my firebox (about 34"W x 28"H x 15"D(+ the 10" extension)), it seems that may be difficult without getting a very small viewing area.

    Thanks for the help, just looking for some quick guidance so I can figure out if I should buy this mantle from the antique store before someone else does.

    Thanks again, Nathan

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  2. DAKSY

    DAKSY Patriot Guard Rider Staff Member

    Joined:
    Dec 2, 2008
    Messages:
    4,891
    Loc:
    Averill Park, NY, on Burden Lake II...

    The only thing I've done in this situation is to build a fireproof shell out of Durarock mounted to steel studs to make up the space. It will have to be mounted to the facing & RTV silicone should also be used to eliminate any gaps on the top & sides. Then the mantel can be mounted to the shell. If you're going to get this install inspected, you will have to get the blessing of the Authority Having Jurisdiction (AHJ) - aka building inspector. It can be done & it can be done safely...Good Luck!
  3. nate5280

    nate5280 New Member

    Joined:
    May 12, 2013
    Messages:
    2
    Loc:
    Denver
    Wonderful, that sounds easy enough to do, I have enough room the Durarock can just seal to another piece in front that I can face with tile to fill in the gap between the wood surround and the insert, and in back just continue it directly into the firebox.

    The Durarock is only a 1/2" or so thick, do you add additional insulation behind? If I wanted total overkill, would be pretty easy to fill with concrete if I boxed it off, but even easier to just pack in some insulation, like rockwool . Any thoughts?

    Thank you so much. The antique surround is pretty special and I am excited I can make it work. It is late 1800's cherry with hand engraving.

    No inspection luckily, going to keep the old surround intact so if ever sell can just remove the antique one and mod back to a regular install if needed.

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