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Hearth Extension Question

Post in 'The Hearth Room - Wood Stoves and Fireplaces' started by Tom Hearth, Nov 16, 2012.

  1. Tom Hearth

    Tom Hearth New Member

    Joined:
    Nov 16, 2012
    Messages:
    2
    Hello, I am new to the forum, so please forgive me if I'm asking basic questions.

    I recently bought a home with a wood fireplace. The firebox is 10 inches off the floor, is probably 50 years old and is supported underneath by concrete and sits on a foundation wall (the house was added onto). My house has a crawlspace and the crawlspace has a dirt floor. I have been unable to use the fireplace much because there is no hearth extension and embers drop directly onto a hardwood floor (see photo).

    My question is about a hearth extension. I built a 20inch x 6ft x 2inch precast concrete hearth extension that I plan to place directly below the firebox. It weighs about 300lbs and I was planning on just setting it on the floor, using silicone underneath and on the back to hold it (though it wouldn't be moving at 300 lbs anyway) and then grouting the join to the firebox (against facing tile). I've attached a picture of the extension.

    Do I need any kind of support underneath the subfloor to support the extension? 300 lbs is a lot, but I've been under the house and the joists run all the way to the foundation wall (below the firebox) and are connected into the concrete.

    Any comments or suggestions greatly appreciated.

    Thanks!
    Tom

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  2. bag of hammers

    bag of hammers Minister of Fire

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    Northern ON
    Tom - not sure I can answer the structural question. I'm curious - why 6" for the extension? Is it because it's a tripping hazard in the corner location (foot traffic)? I think I recall something like 16" or 18" beyond the front of the stove as per my stove install manual, and also being min requirement for fire code? Lots of people here can sanity check that. Sorry not much help but my brain is kinda going towards fire safety vs structural integrity, as a first stop...
  3. DAKSY

    DAKSY Patriot Guard Rider Staff Member

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    Loc:
    Averill Park, NY, on Burden Lake II...
    It says 20" x 6'...That's plenty of protection...

    As for the weight, I am also not a structural engineer, but if you're worried, put some small jacks & a header underneath the area in question. Put some crushed stone down first, maybe a foot deep, then put a steel plate, maybe 12" square by 1" thick on the stone & then a couple of small screw jacks under the header & you should be good to go...
  4. Tom Hearth

    Tom Hearth New Member

    Joined:
    Nov 16, 2012
    Messages:
    2
    I'm in luck as there is already a screwjack directly under the target location....and Bob, you are correct, it's 20 inches x 6 feet.

    Thanks guys
    DAKSY likes this.
  5. bag of hammers

    bag of hammers Minister of Fire

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    1,167
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    Northern ON
    Bob - thanks for that clarification. Apparently I can't tell the difference between and inch and a foot. Tom, apologies for my tired eyes and the noise.
  6. David Tackett

    David Tackett Member

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    Oct 17, 2012
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    178
    Loc:
    Waynesburg, Kentucky
    Sounds like a great deal.

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