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Thread: Should all the tiles be installed with thinset?

  1. #1
    DIY Junior Member Maxie's Avatar
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    Default Should all the tiles be installed with thinset?

    Ok, another thing I'm questioning with my contractor. He's going to lay the tile and said he will be using thinset in the tub/shower surround and mastic for the rest of the room. This is a 5x8 bathroom and will be tiled to the ceiling in the shower, and 4ft high for the rest. I was reading up on thinset vs mastic, and it sounds to me like the entire room should be done with thinset since it's a bathroom and is a wet environment. The walls will be 3x6 subway (with a mosaic accent strip running around the room), and the floors are 6x24 porcelain "wood" planks.

    Should all the tiles be installed with thinset? And why would he even bother switching to another compound for such a tiny space?

  2. #2
    DIY Senior Member dj2's Avatar
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    The troubles you have with your subs...

    The only time I'd use mastic, is for kitchen walls/backsplash. Everything else gets thin set.

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    DIY Junior Member Maxie's Avatar
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    I know. What do you do when you realize you may not have hired someone with the quality standards you thought they had? I was thinking of asking the GC how much more it would cost me if he put the best tiler he knows on the job. He said if glass tiles are involved, there's someone else he uses.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    It is highly likely that the floor tile is beyond the mastic's capabilities, and even then, is not a great idea. Mastic must DRY OUT to provide its bond...it stays viable in the bucket on the store's shelf for months because the bucket is sealed and it can't dry out. Guess what happens underneath a nearly impervious porcelain tile? There's a size limitation on pretty much every mastic that I've ever looked at. You do NOT want mastic on the floor. While your bathroom floor shouldn't see much liquid water, keep in mind that mastic will soften in liquid water. Thinset is a cement based material, and CURES (you don't really want it to dry out!) to gain its ultimate strength. Well, if you use a modified thinset, it must both dry AND cure to provide the bond, but the curing happens better in the presence of moisture, and that can provide the bond and hold while the modifiers dry.

    But, considering he is planning on mastic, what is the actual subfloor and joist structure? What's he planning on putting there? There are some fairly strict industry standards on what is required for any reliable, long-lasting tile job. So, a bit more info on that may avert a disaster.

    www.johnbridge.com is dedicated to tiling issues and might be a good resource to check up on things.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  5. #5
    DIY Junior Member Maxie's Avatar
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    I think he will use thinset on the floor (contract says Tile installed over setting bed with latex fortified Portland cement mortar), but mastic on the walls outside the shower. According to the contract, he will either do a tradition "mud job", with 15lb felt over wood substrate and galvanized wire lath over felt, with a portland cement and sand setting bed, OR, use exterior grade CDX sheathing with resin coated fasteners and the felt and wire lath.

    Great tip on the tiling website.

  6. #6
    DIY Junior Member Maxie's Avatar
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    Is a latex fortified Portland cement mortar a modified thinset? Is it wrong to use that in the shower area? That's what he says he's going to use and if it's better to use a regular, or unmodified thinset, I would want him to do that.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    A modified thinset, when installed properly, is stronger than a dryset (unmodified), so the use of it in a shower is fine.

    Re the mastic on the walls; IF the tile size is within range of the mastic chosen (bigger tile cannot be successfully installed with mastic), then it is okay, but it actually costs more than thinset in materials. The advantage is you don't spend time mixing it, and then cleaning up your bucket and paddle or throwing away some that begins to set before you can use it.

    I am concerned about the floor install. What you describe is NOT an approved, tested installation procedure. It is common, but it has never been successfully tested in a long-term install. It is commonly referred to as a Jersey Mud job. It does not show up in the Tile Council of North America (TCNA) handbook, because if fails the Robinson field test, the industry standard for suitability of installation methods.

    There is certainly more than one approved method to install floor tile, and the only one I'm aware of that uses lath is one by Mapai (you can look it up on their website, but it uses their plastic lath material and a very specific mortar) or a full reinforced mudbed, which over a wooden subfloor must be at least 1.5" thick. There is no other tested/approved method of tile setting using lath that I'm aware of. Have the guy show you an approved method from the TCNA handbook that matches his plan...he can't! Probably doesn't know what it is, but it is the golden industry standard.

    The more common methods in use are a cement board (cbu - like Hardie Board), or a decoupling membrane (like Ditra). Both of those, if installed per the manufacturer's instructions, are reliable and work well.

    You never did answer what the subflooring and joist structure consists of. If that is not up to industry standards, nothing you put on top of it has a reliable chance of survival, regardless of the method. Every approved method starts with a suitable substructure.
    Last edited by jadnashua; 09-20-2013 at 11:30 AM.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Junior Member Maxie's Avatar
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    The subfloor is plywood and I don't know the thickness (and am not at the house to measure it). The old floor was replaced with a new piece. I don't know the size of the joists. I assume it's whatever was typically used in 1963 for a floor over a basement. Lame answer I know. Are these other methods more expensive? (is that why he wouldn't use mapai or Ditra?)

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    Retired Defense Industry Engineer jadnashua's Avatar
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    It shouldn't be a question of cost, it should be a question of if the method selected has been approved and tested by the industry. There are lots of people doing things 'their way', and they may have been doing it for a long time, but that doesn't mean it is correct or will last. You're paying for it, you want it done according to an accepted industry standard. When you consider labor, something like Ditra comes in about the same cost of cbu installation, and maybe only slightly more than a Jersey mudbed, and both of those would be warranted by the manufacturer and are industry approved methods that will survive (unless your structure is inadequate, then all bets are off!).

    Now, if they're doing a full mudbed, that's good, but it will need to be at least 1.5" thick if it's done right over a wooden subfloor. What is more likely, is a thin layer of mortar over the lath then the tile laid on top. That is NOT acceptable!

    Sorry, but there are lots of floors built that do not meet the industry standards for acceptability for tile installation, so the age of the structure is not sufficient. Hopefully, the tile you've selected is ceramic and not a natural stone. Natural stone requires a floor twice as stiff and other prep work to survive, and almost no homes (that didn't have it in originally) are/were built strong enough to support natural stone. Sometimes, it's not hard to make it work with natural stone, but each situation is different.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Master Plumber kcplumber's Avatar
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    I have seen mastic that was 2 years old and still never setup. I am a fan of using thin-set, especially in a shower or floor.

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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Mastic should be used - well, almost never.

    Total crap. Good for small tile in a dry zone and never underfoot.

    I would be double checking everything your contractor told you and stopping the job before you get to far along. Sounds like an uneducated renovator to me.


    jfrwhipple@gmail.com - www-no-curb.com - 604 506 6792

    Always get construction advice double checked by your local city hall. Flood Test Every Shower - Every Time.

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    builder:anti-builder dhagin's Avatar
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    Hi Maxie.

    Sorry about your contractor troubles. For all your tile install or prep questions, do yourself a favor and check out johnbridge.com. These folks are seasoned, respectful and friendly dedicated tile professionals, not just internet play contractors.

    Many DIYers and homeowners have been helped and they can walk you through your project step by step. Give it a look.

    http://www.johnbridge.com/vbulletin/...isplay.php?f=1
    dana
    __________________________________________________ ______________________
    in my youth, i knew it all and treated folks like they knew nothing. after 3+ decades in the construction business, i came to realize that the more i learn, the less i know. now i treat folks as i want to be treated - with respect, no matter how little i know. :-)

    Note: please don't feed or quote trolls. thank you. :-)

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