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  1. #1
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    Default Mantel projection

    Can someone please explain the mantel projection standard(s). In detail. Just want to double check and make sure that I understand it correctly.
    Thanks in advance

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  2. #2
    Ray Norton's Avatar
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    Default Re: Mantel projection

    This is what the 2009 IRC R1001.11 exception #4 says:


    Exposed combustible mantels or trim may be placed
    directly on the masonry fireplace front surrounding
    the fireplace opening providing such combustible
    materials are not placed within 6 inches of a
    fireplace opening. Combustible material within 12
    inches of the fireplace opening shall not
    project more than 1/8 inch for each 1-inch distance from such an opening.

    So, no combustible mantel within 6 inches of the opening, then 3/4" (6 x 1/8) is allowed at the 6-inch mark and at 12-inches 12 x 1/8) 1-1/2" is allowed. After that there is no requirement.



  3. #3
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    Default Re: Mantel projection

    Quote Originally Posted by Ray Norton View Post
    This is what the 2009 IRC R1001.11 exception #4 says:




    Exposed combustible mantels or trim may be placed
    directly on the masonry fireplace front surrounding
    the fireplace opening providing such combustible
    materials are not placed within 6 inches of a
    fireplace opening. Combustible material within 12
    inches of the fireplace opening shall not
    project more than 1/8 inch for each 1-inch distance from such an opening.


    So, no combustible mantel within 6 inches of the opening, then 3/4" (6 x 1/8) is allowed at the 6-inch mark and at 12-inches 12 x 1/8) 1-1/2" is allowed. After that there is no requirement.
    So you are saying above 12" I can essentially have a mantel project 24" outward? Guess i was over-thinking it. The 1/8th thing confused me.

    Last edited by Marc M; 04-25-2011 at 04:53 PM.
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  4. #4
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    Cool Re: Mantel projection

    First of all, for factory built fireplaces, you always refer to the listed instructions for mantel clearances. The code references are strictly for masonry fireplaces constructed to that code and do not apply to freestyle creations of architects and adventurous pyromaniacs. Note some fireplaces, esp. B-vented gas fireplaces usually have mantel requirements that will exceed this clearance. Also, ventfree gas fireplaces will have a much greater clearance. Usually, they will allow a reduction in clearances with the installation of THEIR 4" canopy. However, I've seen where the marble header cracked from excessive heat on these so that still doesn't make it right.

    Marc, after 12", it would fall back on the AHJ.

    FWIW, I found one on a factory built fireplace 53" deep with stone veneer over OSB forming a tunnel at zero clearance to the firebox opening. It had a $25K plasma TV 3" above the opening. This was a custom buildes home that had just been rebuilt from a fire caused by the factory chimney to the indoor pizza oven having two 30* ells doubled up and he tries this nonsense. Also had an unlisted shroud over two direct vent terminations. Yes, he got a cert. letter...

    FYI, most of the cast mantels hitting the market have NOT been tested to ASTM E-136 for non-combustible rating. Therefore, when in doubt, refer it to the AHJ. One exception might be certain mantels that are actually listed for use with certain model fireplaces. I know HHT has done with this much of their product line since they now mfr. both mantels (cast and wood) mated to their specific fireplaces.

    HTH,

    Keep the fire in the fireplace.

  5. #5
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    Default Re: Mantel projection

    Your reference, since you are in California, is Title 24, Califronia Residential Code, RIOOl.ll Fireplace clearance. The code is free for download at:
    bulk.resource.org


  6. #6
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    Default Re: Mantel projection

    Here is a Heatilator Install Manual spec. This is for a gas insert.

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  7. #7
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    Default Re: Mantel projection

    I thought there was no minimum clearance after 12 inches.

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  8. #8
    Ray Norton's Avatar
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    Default Re: Mantel projection

    That is the way I read the code for masonry fireplaces, yes. Pre-fab fireplace clearances are governed by their listing or manufacturer's requirements.


  9. #9
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    Default Re: Mantel projection

    Roger that....

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  10. #10
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    Default Re: Mantel projection

    One more thing, Marc. Check out the 1 day course at www.gotofire.com from the ad associated with this thread. They run the course several time a year in Moorpark, CA, not too far from us. I took the course this spring and can say I have a much better understanding of the principles of fireplaces and gas appliances that I could learn from the codes alone. Well worth it.


  11. #11
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    Default Re: Mantel projection

    Thanks, I know Dale very well.
    This was one of those things where you think you know something so well, for so long; and then someone tells you something different, It makes you start to think.... thus the reason my post was stated in the manner it was.

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  12. #12
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    Default Re: Mantel projection

    Quote Originally Posted by Bob Harper View Post
    First of all, for factory built fireplaces, you always refer to the listed instructions for mantel clearances. The code references are strictly for masonry fireplaces constructed to that code and do not apply to freestyle creations of architects and adventurous pyromaniacs. Note some fireplaces, esp. B-vented gas fireplaces usually have mantel requirements that will exceed this clearance. Also, ventfree gas fireplaces will have a much greater clearance. Usually, they will allow a reduction in clearances with the installation of THEIR 4" canopy. However, I've seen where the marble header cracked from excessive heat on these so that still doesn't make it right.

    Marc, after 12", it would fall back on the AHJ.

    FWIW, I found one on a factory built fireplace 53" deep with stone veneer over OSB forming a tunnel at zero clearance to the firebox opening. It had a $25K plasma TV 3" above the opening. This was a custom buildes home that had just been rebuilt from a fire caused by the factory chimney to the indoor pizza oven having two 30* ells doubled up and he tries this nonsense. Also had an unlisted shroud over two direct vent terminations. Yes, he got a cert. letter...

    FYI, most of the cast mantels hitting the market have NOT been tested to ASTM E-136 for non-combustible rating. Therefore, when in doubt, refer it to the AHJ. One exception might be certain mantels that are actually listed for use with certain model fireplaces. I know HHT has done with this much of their product line since they now mfr. both mantels (cast and wood) mated to their specific fireplaces.

    HTH,
    Good information, thanks BOB. It's funny, I had my doubts about some of the cast fixtures as well.

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  13. #13
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    Default Re: Mantel projection

    There is a TV that costs $25,000? I guess they really, really, like to watch TV. That seems a little excessive, but if you earned the money I guess you can spend it on whatever you want.

    Jim Robinson
    New Mexico, USA

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