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Thread: Installing cement board behind my shower

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    DIY Junior Member KatrinaK's Avatar
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    Default Installing cement board behind my shower

    Hi Everyone,

    I am remodeling my bathroom and am at the stage where I need to put the cement board up behind my shower. There is some vapor barrier there, but on the interior walls it only goes about half way down the wall. Does anyone have any thoughts on if I need to add more vapor barrier? There used to be drywall behind the shower, I'm not sure if having cement board now changes things?

    Also, I am not sure how far down the cement board should go. The drywall that was there previously looked like it was just above the tub line, not touching it. This is one of those shower/tub combos.

    Any thoughts on this would be greatly appreciated, I am very new to the do-it-yourself world!

    Katrina

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    You do want a vapor barrier and bring it down lapped over the tub's tiling flange. You only need the cbu up to the height of the showerhead, but you can go further. To keep the cbu from bowing out, you can shim the studs, notch the studs (and recess the tub's flange so it is flush with the studs), or stop it slightly above the flange and make sure the tile is more than half supported on the cbu. The tile should not be touching the tub, but a slight gap that is caulked.
    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 KatrinaK's Avatar
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    Thank you Jim, this helps a lot !

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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 04:39 AM.


    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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    DIY Junior Member galerie's Avatar
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    Can LATICRETE Hydro Ban be installed on Durock Backberboard?

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    In the Trades mtcummins's Avatar
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    Correct me if i'm wrong, but I believe you should NOT have both a vapor barrier behind CMU and waterproofing over it. Its one of the other, and the waterproofing over CMU is the better option by far.

    Personally, I use Kerdi on walls and Ditra on floors with modified thinset (typically versabond), with no problems. I know that John Bridge over at his excellent tile forum (that JW above doesn't seem to like too much) does the same at least with Ditra, and he's been doing it a long time w/o problems. However, it will void the warranty if you're worried about such things, so its your call. The other options he suggested are also good ones, I just happen to like Schluter's products.

    Can't tell you about hydroban on CMU, maybe someone else can, or read the specs on it. it should tell you the suitable applications.

    With most waterproofing, CMU is overkill, though I like its stability and sometimes will use it. With Kerdi, I generally just apply directly to MR gyp board. Not sure what the other waterproofing methods require, but this is how Kerdi is specified to be installed.

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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 04:39 AM.


    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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    Retired Defense Industry Engineer jadnashua's Avatar
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    I welcome opinions, but everyone should consider that the people expressing them, myself included, are individuals, and we're all different. Re John Bridge's forum...John Bridge has probably tiled more years than John Whipple has been alive. The fact he is now retired is somewhat irrelevant...he has more time to look at new products. His site has numerous professionals that make their entire living doing tile projects, and has many more opinions, than this forum. They have Latticrete and Noble reps that can answer questions and, while John preferred Schluter products, he and others have and continue to use others when the situation dictates. So, regardless of whether he is retired or not, there are many others that are there, including a structural engineer, available to help. You, as an individual, have every right and the responsibility to look at your options and make your own decisions as to what is best for your situation. Just like Terry doesn't answer every question, on the John Bridge forum, you wouldn't expect him to answer all of yours...you'll get many opinions with enough pros to often get some relevant choices, backed up by years of experience.
    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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    Moderator & Master Plumber hj's Avatar
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    Vapor barrier is ONLY effective, or needed, when there is a temperature differential between both sides of a wall. An interior wall does NOT have that differential
    Licensed residential and commercial plumber

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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 04:39 AM.


    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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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 04:40 AM.


    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.

  12. #12
    Moderator & Master Plumber hj's Avatar
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    Another thing. The vapor barrier is installed on the "heated" side of the insulation and its purpose it to prevent that "moisture" from getting into the insulation, where it would condense into "real" water, NOT keep it out of the wallboard or "stud space".
    Licensed residential and commercial plumber

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    Retired Defense Industry Engineer jadnashua's Avatar
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    In John Bridge's first book, he said he used Versabond, but later on, he came to agree with Schluter, that a good unmodified was more than adequate, and I think his second book shows that. While other good dryset mortars are available, the formulation of DitraSet swayed him, I think along with discussions with the manufacturer. The reason Versabond worked, is that is it only slightly modified, and drying isn't as critical for it as for some others...it's close to a reasonable quality dryset with a little kick, if you will.

    Lots of people flood test their showers there. There are numerous pros that comment in the forum, and a lot of DIY'ers, too, just like here. The only time the thickness of the membrane might be an issue from a durability point is during construction where you may have it uncovered and say step on it with some debris (say a nail or screw). The beauty of the sheet membranes like that is that you can do the walls (almost to the pan), then do the pan so you don't have to walk all over it in the interim. Plus, because the stuff is thinner, you get less buildup in the corners and junctions. I have no problems with people preferring other materials. My limited experience and training is with Kerdi, and it's met my needs and desires. I do believe that if you are conscientious about getting good coverage with the thinset and the proper overlap, that a flood test with Kerdi is somewhat overkill, but certainly doesn't hurt. And, if the local code officer wants one, it should be done, regardless. They do highly recommend you get a permit and the subsequent inspections.

    Once you've done a few, it's easy to tell visually if you've got a good bond, and bubbles and ripples are easy to spot (and shouldn't be there in the first place if you install it well). Painted or rolled on materials are absolutely required to have a flood test, as it's easy to have a pinhole leak, or insufficient coverage. A traditional liner would be foolish to not do a flood test, as it typically needs to be cut and patched for the curb, then you have a thin clamping drain that you may not have screwed down evenly or tight enough. On the Kerdi shower I built for my mother, the inspector came, looked it over, approved it without a flood test. He understood the material, and inspected the construction quality. I was trying to complete it over a brief Christmas holiday, in between entertaining, while 400-miles away from my own home, so time was important, as was the availability of the inspector to come without losing lots of time because of the holiday and having to wait potentially days in between his visits.
    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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    ACO Shower Drain Sales johnfrwhipple's Avatar
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    post(s) deleted by John Whipple
    Last edited by johnfrwhipple; 03-17-2014 at 04:40 AM.


    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. #15
    Retired Defense Industry Engineer jadnashua's Avatar
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    Quote Originally Posted by johnfrwhipple View Post
    So if you use the thinnest membrane out there it's OK to skip a flood test, but if you use any other system then it is necessary. That's funny.

    I frequent the John Bridge site weekly and no one recommends flood tests. Who are these posters you refer to?
    Not what I said...a traditional pan liner, absolutely, a paint on membrane, absolutely, a properly installed sheet membrane, always a good idea, but kind of overkill. The beauty of a membrane, is you can even tile the walls before you even build the pan...so, you leave the bottom row off, install the pan and then seam that joint. You can water test then. Then, tile the floor. Much less chance of damaging the pan liner. If you happen to drop a trowel after your flood test, you'd be in the same situation.

    Since most places require a water test, this discussion is kind of mute, and, the guys over there regularly tell people to get a permit and inspection. So, there's a flood test. When you tell your kids to get dressed, do you have to tell them to put their shoes on too? Hopefully not if they're older than say six.

    A DIY'er could do a flood test and not tile for weeks...the test is kind of useless unless they are very conscientious about protecting the material. For that, a traditional pan is probably better, since the mortar bed protects it.
    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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