Installing cement board behind my shower

Discussion in 'Shower & bathtub Forum & Blog' started by KatrinaK, Nov 14, 2011.

  1. KatrinaK

    KatrinaK New Member

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    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. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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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.
  3. KatrinaK

    KatrinaK New Member

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    Location:
    Toronto ON
    Thank you Jim, this helps a lot !
  4. johnfrwhipple

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

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  5. galerie

    galerie New Member

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    Can LATICRETE Hydro Ban be installed on Durock Backberboard?
  6. mtcummins

    mtcummins In the Trades

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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.
  7. johnfrwhipple

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

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  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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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.
  9. hj

    hj Moderator & Master Plumber Staff Member

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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
  10. johnfrwhipple

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

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  11. johnfrwhipple

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

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  12. hj

    hj Moderator & Master Plumber Staff Member

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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".
  13. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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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.
  14. johnfrwhipple

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

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  15. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    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.
  16. johnfrwhipple

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

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  17. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    "flood test" got hits on 280 threads over there in the DIY'er section. Building permits are often mentioned. I get nothing from any site I participate in except a way to keep my brain agile. Anyway, enough of this...I think we actually agree on more than we disagree on, and it's not pertinent to this thread.
  18. johnfrwhipple

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

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  19. dlarrivee

    dlarrivee New Member

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    John, why don't you give it a rest already...?

    What does your problem with the JohnBridge Forum have to do with this thread?
  20. johnfrwhipple

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

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