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Thread: laying tile floor - what is proper subfloor?

  1. #16
    DIY Member Don Zorn's Avatar
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    Kavita - This only applies under tiles.

    I too thought this was strange and counter intuitive - but learned this tip from a couple of professional tile mechanics. Here's the reason:

    If you screw the top layer of ply into the joists and there is any movement in the joists, it is more likely to transmit that movement to the tiles - which can lead to tile/grout cracking. In tile setting any movement of the subfloor is considered bad.

    If you only screw the top layer of ply to the subfloor below, movement in the joists is not quite as likely to get transmitted to the upper layer of plywood - in effect decoupling the joists from the top ply. Albeit the bottom layer is still screwed into the joists and the top layer is screwed into the bottom layer so they are still coupled indirectly - but at least not directly.

    I personally believe that if you don't follow this advice, it is not a catastrophe, but if you do follow it, it is just one more step that will only help to make your tile installation more successful. Good tile meachanics subscribe to this methodology - feel free to ask on the Floorstransformed ceramic tile forum.

    In my opinion, you should be OK without waterproofing you bathroom floor before tiling as long as you don't leave standing water for long periods of time on the tiles.

    My $.02 - worth the price charged!

    Good Luck.

    Don

  2. #17
    DIY Member Don Zorn's Avatar
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    Default Underlayment Joint Position vs. Subfloor Joint Position

    Kavita - If you are interested, read this article for more tips on how to place the underlayment (ie. top layer of plywood) relative to the sub-floor (bottom layer of plywood) in order to reduce tile cracking.

    http://www.tile-assn.com/tileletter/...oeste-0604.pdf

    Don

  3. #18
    DIY Member GregO's Avatar
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    I understand what Don is saying, but Don, I somewhat disagree with you. Please hear me out... Atop of plank flooring, firmly securing the plywood is critical to ensure a stable substrate. Atop of that plywood, a tile underlayment should then be placed (e.g., hardibacker, durock, wonderboard, etc.) The specific tile underlayment is what needs NOT be secured to the joist, but obviously to the subfloor only the depth of the subfloor.

    There is no way I would only secure plywood only to the plank flooring and not the structural timbers; that would be asking for trouble.

  4. #19
    DIY Member Don Zorn's Avatar
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    Greg - I hear ya. I thought the same thing - screw the underlayment right through the subfloor into the joists = nice solid floor = less tile cracking. But apparently I was wrong. It is even listed in the TCA handbook - only screw the underlayment into the subfloor.

    Now this is for a plywood underlayment with plywood sub-floor. Maybe with plank subfloor it is different. That I am not sure about.

    Don

  5. #20
    Retired Defense Industry Engineer jadnashua's Avatar
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    Prior to putting down the plywood, make sure that the planks are firmly attached to the joists - it wouldn't hurt to add some screws, then nail (or screw) the plywood to the planks, avoiding the joists. If nailing, then use ring-shanked nails. If you hit a joist when doing the plywood, don't worry about it, but try to avoid them.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #21
    DIY Member kavita's Avatar
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    Default evenin' up before the durock

    first, thanks for all your responses last month.

    can't believe it's been a month since last visit. left behind the tiling projects for other refurbishing tasks; now returning to the tile floor and have another couple preparation questions. (yes, also listing on johnbridge.com but the responses there can be somewhat daunting!)

    i considered all your input and the ply subfloor is attached to what's beneath. i appreciate your musings, intuitive and counter-, on the subject.

    i'm finally about to lay the durock ...

    - would you please offer suggestions for a floor levelling product to add in a couple of areas between the plywood subfloor and the durock i'm about to lay?

    there's a slight unevenness apparent in a couple areas now that the ply's down and i want to correct it. i've been told LevelBest would work, but i've heard also that a mortar mix is sufficient/preferred. your thoughts? your product recommendations?

    - once the durock is in place, what do you suggest using to level the areas where the durock sheets meet and a depression exists? i understand the thinset might be sufficient for this, but i'd like to hear any of your ideas.

    many thanks - i appreciate your help so much.

    kavita

  7. #22
    Retired Defense Industry Engineer jadnashua's Avatar
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    Depends on how big the dips/hills are. From what I read, it is better to level after installing the cbu. If the depressions aren't too big, you can use thinset. Use the longest straightedge you have, the longer the better, and see how far off the floor is. Once the amount is known, that will help decide the best product to fix it. Self-leveling cement can be used, but it can be costly. Works great, though. Flows like pancake batter, sets quick, and makes a really nice flat floor for tiling.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  8. #23
    DIY Member kavita's Avatar
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    Default thanks

    jim, jimbo, don, & greg,

    guess this thread can close now but want to say thanks to you all for your ideas, suggestions, referrals.

    all tile sites you recommended and materials therein have been most useful.

    the tile council of america handbook (tileusa.com) is a great downloadable resource.

    the article on underlayment specs (the TIleLetter article) is excellent - really helped me understand that perspective.

    floorstransformed.com is really easy to navigate and get answers quickly.

    johnbridge.com is, well, awesome and dense with information!

    ceramic-tile.com also has a wealth of helpful info - unfortunately, i have a tediously slow dial-up account and the advertising slows down any desired mobility on my end.

    anyway, i REALLY appreciate your time and patience.

    see you when i tile the next bathroom - this time walls and backsplash!

    kavita

  9. #24
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    For areas that get wet, a membrane is not a bad idea, especially with a wood subfloor. If you wipe up spills, it shouldn't be a problem on a normal floor. Moisture does get through the grout but it takes awhile. If you have kids that slosh water all over the floor each time they shower or bathe, then it may be a good idea. Tile should stay until you tire of it, not because of a failure. So, depending on the circumstances, waterproofing the subsurface helps. An isolation membrane is not necessarily waterproof - you need to follow the procedure to seal the butted up seams. It does provide crack resistance, regardless of whether you seal the joints or not, and is often used without sealing them.

    Here is my what my hubby that you maybe interested in....

    http://justkitchenbacksplash.com/kit...ash-ideas.html

    check it out

  10. #25

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    In addition to the great points discussed here, I would also note a couple of things about membranes like Durock Tile Membrane.

    -totally waterproof and impermeable
    -can lay directly over the existing flooring, so you don’t need to rip out old flooring
    -super thin, so it won’t raise the profile of the floor.
    -guards against tile cracking by giving some flexibility to the underlayment

    Some more details here:

    http://www.dtm4me.com/?cid=terrylove

    And some installation videos here:

    http://www.youtube.com/watch?v=U7EgvohEcF8



    http://www.youtube.com/watch?v=Hve-sidUjRM



    Full disclosure: I work with USG, but this seems like a good addition to the conversation.
    Last edited by Terry; 07-18-2010 at 07:21 PM.

  11. #26
    DIY Junior Member Robin Wisdom's Avatar
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    Cool Garage Conversion

    First, thank you so much for your web site. It is a wonderful resource for those of us who prefer to do our own work. I have learned a lot and I am so glad I found you before going forward. My house is 46 years old and on a concrete slab foundation. The garage portion (next to the kitchen) is 4 inches lower than the rest. We have tiled the kitchen with ceramic tile and now wish to continue the tile into what was the garage but will now be the laundry room. So after reading your message board I tried to come up with a plan for the sub-floor. How does this sound?
    1. Build a structure of 2X3s with 8 inches of space between the boards. The 2x3s would be standing up on their side so that the height is actually 2 inches.
    2. Lay down inch exterior plywood and screw into the 2x3s every 8 inches.
    3. Lay down inch exterior plywood (the opposite direction) and screw to the inch plywood but not the 2x3s.
    4. Apply un-modified thin set on top of the plywood.
    5. Lay down inch Hardy Backer Board leaving 1/8 inch gaps between and inch around the outside edges. Screw it down with those big backer board screws and apply the mesh tape & thin set to the gaps.
    That all adds up to 4 inches which will give me the proper height. Originally I was going to use 2X4s for the bottom structure which would have been 3 inches high, inch plywood, and inch backer board, for a total of 4 inches. But, after reading your message board I realized that I would not have 1 1/8 inch minimum under the tile. With the scenario above I will have
    1 inches under the tile. Is that too much? Also, if you have a better suggestion please let me know. I eagerly await your response.

  12. #27
    Retired Defense Industry Engineer jadnashua's Avatar
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    Most garage floors are not made to be level...they usually have a pitch, either to a drain in the middle, or out towards the door. Your plan doesn't take that into account, or the possible irregularities. A better solution, but heavy work, would be to level it off with a mudpack. this is esssentially mostly sand with enough portland cement to hold it together (same as what's used in making a shower pan - 5-6:1 sand/cement). You could make this dead level at exactly the height you want. It's like working with wet beach sand. You could mix it right on the floor with a (special) hoe so you don't have to transport it far. The sand is dirt cheap, and you don't need much cement. Check out www.johnbridge.com. Your plan would work (except for the possible pitch and irregularities), but keep in mind, there is no reason to use thicker cbu than 1/4" on a floor except to match up heights. CBU has very little resilient strength, and will bend (and then hold after a while) to conform to any irregularities. Good ply is better, and more is better yet. You want ply with exterior or exposure 1 rated glue, and the sides C or better (no D side(s)). T&G ply would keep the short edges supported and save having to block there as well. This stuff starts to get expensive, and time and ultimate result means a mud floor should be cheaper, and maybe faster. If you have a boiler, it would also give you the opportunity to add radiant heat tubing to keep the space nice and toasty.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  13. #28
    DIY Junior Member login's Avatar
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    I think cupping in Ceramic Tiles is the common problem and caused by moisture imbalance through the thickness of the wood.To control this u can to identify and eliminate the moisture source. ..this is the single solution of this problem....

  14. #29
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    Wow.

    There is a lot of information in this thread and it is all over the place. A quick scan for "how to", can leave your head swimming with details and one wrong post you read can be the downfall of your entire renovation.

    There are many different ways to construct a subfloor and many requirements that need to be met. I would suggest that anyone first visit the TTMAC and NTCA websites and look there for recommended sub floor assemblies - look for one that fits your home or install the closest.

    Laying 5/8" sheathing, 1/2" ply, 1/2" cement board, ditra, Nobel TS, Flex Therm Cables and on and on all finely tune the sub floor make up.

    When looking for answers you should understand what deflection criteria you need. What the requirements of the tile are for install (ie modified or unmodified). What's the thinest your setting materials can go to (ie 1/4", 3/4" etc).

    This is not a simple question to answer.

    I have to do many rebuilds for clients when I come to waterproof their shower. The number one failure I see in the DIY market is poor fastner and tool selection. You can't board these rooms many times with a re-chargable 12 volt drill. So many times I come in and it was the homeowners drill had no 'Balls' and the wall boards and sheathing is moving around like crazy.

    Often we will prep these rooms for not as adventourous clients and leave the tile setting to them.

    Deflection.

    Bond Breakers.

    Look up these terms and understand them first fully. Before learning how to build your new subfloor.

    Good luck.

    JW


    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.

  15. #30
    ACO Shower Drain Sales johnfrwhipple's Avatar
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    With today's tile choices getting larger and larger and more and more homes being designed with open spaces - control joints, expansion joints and mortar fatigue are very important considerations.

    Yet more research for you before planning your new subfloor.

    This is a tricky process - the tile trade. Never have I found a one system fits all - ever.

    Work with a PRO.

    Look for those who are members of TTMAC or NTCA.

    Hire someone with insurance.

    Ask for a written description of how the floor will be built and tiled and what the time line will be. Before proceeding look into the proposed approached.

    It's Easy. Fast. Quick. Weekend Project. are terms and phrases you will never hear me repeat in front of a client. Often online the advice you seek is mapped out this way.

    Dig deeper.





    http://www.terrylove.com/forums/showthread.php?52614-Tiling-directly-to-Exterior-Glue-Plywood-(EGP)-Tiling-Tips-Pros-and-Cons


    JW
    Last edited by johnfrwhipple; 06-30-2013 at 12:37 PM.


    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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