Whats the difference between thin-set mortar and latex mastic? Whats more common?

Discussion in 'Shower & bathtub Forum & Blog' started by Arsinek, Apr 14, 2013.

  1. Arsinek

    Arsinek New Member

    Messages:
    15
    Location:
    Florida
    So Im about to start cutting my cement board and I came across something that said use the rough side of the board for thinset mortar and use the smooth side for latex mastic. I havent bought my tile and supplies yet so I dont know what Im going to be using. Whats the difference between thin-set mortar and latex mastic? Which should I use?
  2. Arsinek

    Arsinek New Member

    Messages:
    15
    Location:
    Florida
    After looking around it looks like I want to use thinset. Mastic apparently isnt supposed to be used where theres high amounts of moisture.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Location:
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    REal thinset is a cement based product that cures into a rock-hard adhesive. It comes dry and you must mix it with the specified liquid (often just water). Mastics (sometimes they're incorrectly labeled thinset!) are a glue, pre-mixed in a bucket. They need to dry verses a thinset curing. The thing with a mastic is if it is placed under a nearly impervious tile (like say a porcelain or glass), it may take forever to dry out; and, if it's in a place where it can be continually wetted, may NEVER dry out. Until it dries, it can move around. Also, in the fine print, there's often a size limit on the tile - this again is because the stuff needs to dry, and since it normally does that through the grout line, a bigger tile limits the escape path for the moisture. FWIW, I had some mastic get on a piece of wood trim once. After a couple of months, I was able to wash it off, since water just softened it. Not something you want to use in an area that can get wet. Another FWIW, there isn't much difference in bond between the smooth and rough sides of cbu...don't worry - if you apply the thinset properly, it will stick to either side! If the cbu is being installed on a floor, make sure to use thinset UNDERNEATH it, per the manufacturer's instructions. This is to ensure you get 100% support underneath the cbu. Typically, when used on a wall, you'd put a vapor barrier up on the wall before installing the cbu (in say, a shower) unless you are planning a surface waterproofing material.
    Last edited: Apr 14, 2013
  4. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    post(s) deleted by John Whipple
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  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,051
    Location:
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    Often, thinset is less expensive than mastic. The difference comes in the additional time it takes to mix the thinset, verses just dipping some out of the bucket from the store. Labor can make the difference. But, except for dry areas, like maybe a kitchen backsplash, I'd not use mastic, and then, I'd think twice about it.
  6. suceress

    suceress Member

    Messages:
    159
    Location:
    LA
    I'm glad this question was asked because I was wondering about this. What is "cbu"?

    johnfrwhipple, is there any particular brand of thinset you recommend or does it depend on the tile product being used?
  7. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    post(s) deleted by John Whipple
    Last edited: Mar 17, 2014
  8. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

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    post(s) deleted by John Whipple
    Last edited: Mar 17, 2014
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