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Thread: Mortar vs. Mastic

  1. #1
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    Default Mortar vs. Mastic

    I am supposed to "help" install some wall tiles, on drywall, around a gas fireplace.

    The recommendation from HD is to use mortar, instead of mastic, because of the heat.

    I wouldn't think there is much heat on the outer face of a gas fireplace, but..............

    I have installed wall tiles on drywall with mastic, and floor tiles on plywood with mortar, but have never used mortar on a wall, and certainly not on drywall.

    What advice does anyone have?

    It seems to me that mortatr on drywall should need some sealant.

    No? Yes ?

    And doesn't it tend to "slip"?

    Help!
    In an age when scientists are creating artificial intelligence, too many of our educational institutions seem to be creating artificial stupidity. - Thomas Sowell

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  3. #2
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    Default Re: Mortar vs. Mastic

    I have a similar job coming up, ply backer and I was going to use PL Premium.

  4. #3
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    Default Re: Mortar vs. Mastic

    Mastic is combustible there in lies the rub. so is plywood. I take it its fire code dry wall?
    jack
    English machines

  5. #4
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    Default Re: Mortar vs. Mastic

    If it is a zero clearance fireplace fire rating should not be a concern. There should be documentation with the fireplace setting out clearances required.
    I have done the odd tub wall in tile and have always used thinset mortar on both drywall and Kerdi. I always primed the drywall
    Brian
    Last edited by Brian @ Muir; 08-25-2013 at 08:50 PM.
    If your dreams don't scare you, you are not dreaming big enough

  6. #5

    Default Re: Mortar vs. Mastic

    I've noticed with some of the new zero clearance fireplaces, the wider ones, that they must be surrounded by non-combustibles.

    Get a bag of all purpose thinset. It's polymer modified and quite sticky, not too different from using mastic.

  7. #6
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    Default Re: Mortar vs. Mastic

    Thanks guys. I leave today to get started.
    In an age when scientists are creating artificial intelligence, too many of our educational institutions seem to be creating artificial stupidity. - Thomas Sowell

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  9. #7
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    Default Re: Mortar vs. Mastic

    Hi Gene,

    the heat on the face of a gas fireplace can be tremendous. Especially if it is used often. The mantle above has construction standards to follow as well. The hazard here is pyrolysis. Combustible materials are "cooked" until all moisture is gone and then are ready to ignite.

    http://en.wikipedia.org/wiki/Pyrolysis


    Follow the installation instructions and materials specifications. You may be surprised but a lot of units are engineered to make installation cheap, so they can sell more.

    Don't take fire prevention advice from "the guy" at HD.

    Check the ULC plate on the unit for acceptable clearances.
    Mike


    Whether you think you can, or you think you can't--you're right.
    Henry Ford

  10. #8
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    Default Re: Mortar vs. Mastic

    I've only ever used mastic for thin little kitchen tiles. Use mortar and make the mess.
    Kevin

  11. #9

    Default Re: Mortar vs. Mastic

    Quote Originally Posted by jgarrett forsberg View Post
    Mastic is combustible there in lies the rub. so is plywood. I take it its fire code dry wall?
    jack
    English machines
    Learn something new every day.

    While my insight is too late...

    For lightweight tiles, 6x8 ceramics and smaller in areas other than showers/baths. Mastic is fine. (with the exception of combustible areas apparently)

    For heavier porcelaines and ceramics, or either in a water environment, use thinset. Mastic is food for mould.

    My lads use Ultralite by Mapei for vertical substrates. One prefers Roberts 1412, a PM thinset for horizontal use. He fits into the 'can't teach an ol' dog new tricks' category.

  12. #10
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    Default Re: Mortar vs. Mastic

    The mortar was a "ready to use" type in a pail, it was a called mortar and consisted of sand limestone and two polymers. We put in on over primed drywall, and it worked OK. One issue was that we used the size of the tile "sheets" as a guide, as if they were tiles, instead of a lot of little pieces and used a trowel with notches a bit too big. But it worked out. I never used mortar what was not cement. The tile grout was cement based.

    Regarding clearances, we had to have the city building inspector check the installation before the top could be covered. The actual "chimney" was already covered when he arrived, we explained the clearances and showed the installation instructions, and even offered to cut a hole in the drywall so he could see. He said he didn't want to hassle a homeowner, but

    "if you were a contractor,I'd have to see it, because they always push it."

    This was one guy who didn't think his job was to be a PITA.
    In an age when scientists are creating artificial intelligence, too many of our educational institutions seem to be creating artificial stupidity. - Thomas Sowell

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