Tile over greenboard?

Discussion in 'Shower & bathtub Forum & Blog' started by jhetzig, Sep 12, 2006.

  1. jhetzig

    jhetzig New Member

    Messages:
    7
    I prepared my tub walls for Swanstone but than someone decided we wanted to do tile instead. Seams are taped and spackeled and everything is flat and ready. Can i tile over green board? I remember taking an old bath apart and finding the tile had been glued up on greenboard with mastic instead of thinset and grouted... it had worked just fine. As an alternative i was thinking maybe just he 1/4" hardibacker over the greenboard? What should I do?
    Thanks, Jim
  2. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Check out the tile forum (www.johnbridge.com) for more than you'll ever want to know about tile, showers, baths, etc.
  3. Verdeboy

    Verdeboy In the Trades

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    2,051
    I tile over greenboard all the time. Just get a tub of c-tile glue and a trowel, and of course some kind of tile cutter, and go for it. A recent post suggested that greenboard is no longer code for certain states, but since it's already in place, I'd go for it. Just do a good job of grouting and caulking, and you should be good for twenty years or more. Don't forget to caulk around your fixtures as well.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

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    Location:
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    Put up a vapor barrier, and then 1/4" cbu. Then tile. Grout is not waterproof. The holes you put in to secure the greenboard compromised the surface layer. Drywall compound (at least the premixed stuff in a bucket) will get soft again if it sees moisture. The gypsum in the greenboard is food for mold. If it gets wet, it is ruined, and it is almost certain to do it in a shower.

    Greenboard NEVER was a great idea, and by national code (local may differ) is no longer approved for wet areas. A shower definately is wet.

    Check out that website recommended...they'll set you straight and help - www.johnbridge.com.
  5. jlohrenz

    jlohrenz New Member

    Messages:
    45
    If you don't want to tear down the greenboard you need to look into a product called Kerdi (See johnbridge.com forums). It can be applied in situations like this.
    Otherwise your other options are to pull down the greenboard and put in a vapor barrier and CBU like has been suggested already.

    I just spent the past few weeks tearing out our bathroom (house built in 89) that had greenboard in the tub and shower behind tile. It was mushy as heck and had started leaking. What a mess.

    As stated earlier, I can completely understand why this stuff is no longer allowed in new construction in Tub and Shower areas.
  6. Verdeboy

    Verdeboy In the Trades

    Messages:
    2,051
    I agree that using CBU and a vapor barrier is the better way to go, but I've seen shower areas that have remained in good shape for decades as long as the grouting and caulking have been well maintained. This is just another way of making things "idiot proof."
    Last edited: Sep 13, 2006
  7. shower or tub only? Tub-shower combination?

    The most crucial information is missing, Jim.

    If shower water is going to get on the tiles, skip NO steps; you'll need the vapor barrier. And leave a space at the bottom of the 1/4" Hardibacker so water on the tub itself doesn't have any contact point to it. There is always some way for moisture to get behind tub caulk, and Hardiboard does let moisture inside it, and this will wick...

    If this is a tub-only, you have a few options. One is to do with a less-best option.

    Tile and grout are not waterproof. Moisture goes through grout.

    david
  8. Verdeboy

    Verdeboy In the Trades

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    2,051
    I keep hearing that tile and grout and caulking are not waterproof. If that's the case, then the tile adhesive would continuously get wet and there would be tiles popping out all over the place, regardless of whether you are using CBU or greenboard.

    My experience, especially in the area of multi-unit housing, is that the only time I have to replace tiles and fix damaged greenboard is when grouting and caulking are missing or had not been done properly, and the tenant waits until several tiles have fallen out before calling in the maint. request.
  9. jimbo

    jimbo Plumber

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    This is a case where a technique was used for many years....sometimes there were never any problems, ,,,more ofen than not things were not A-OK under the tile, and that may never have manifested any problems until it was torn down..

    We no know that there are drawbacks to putting tile on greenboard in a shower. There is potential for problems ( mold, etc) AND there are better ways to do it . so why would you not take advantage of the best modern material?
  10. Verdeboy

    Verdeboy In the Trades

    Messages:
    2,051
    I actually agree with you, Jimbo. If I was starting from scratch, I would take the "modern" approach. But the thread starter already has fresh greenboard in place and is ready to go. I think, if he does a good job grouting and caulking, he can rest easy that it will hold for many many years.
  11. Cass

    Cass Plumber

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    5,980
    Location:
    Ohio
    I'm with jimbo.

    Green boards AKA is MR board (moisture resistant). It is not and never was water proof.

    If jhetzig doesn't want to change the board and the MR board is not resting directly on the tub, If the tile & grouting job is done right, If the grout is sealed & caulked & maintained it should give many years of service
    but
    for a few $$$ and 1/2 a days work the job could be far better by installing CB or similar and then never having the worry of a failure or mold growth due to water penetration.
  12. Mikey

    Mikey Aspiring Old Fart, EE, computer & networking geek

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    Location:
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    If the walls are taped, seamed, flat, etc., I would put Kerdi over the greenboard. Not sure how the wall-tub interface looks, but do all you can to keep water from wicking up behind the Kerdi. Color-matched caulk is commonly used, I think.
  13. tub flange: inside or outside your Greenboard?

    more missing information: did you put your greenboard inside or only butting up to the tub flange? This is important.

    david
  14. kamaehu

    kamaehu Junior Member

    Messages:
    1
    Location:
    hawaii
    I've done a few jobs using greenboard. They were usually at the request of the owner, or required by a condo to replace what was originally there (usually a double layer of 5/8" gb for sound installation and fire code). In those cases I've applied a double coat of Red Guard for a water proofing layer before installing the tile and epoxy grout for it's exceptional water resistance, long life, and very low maintenance.
  15. khayes

    khayes New Member

    Messages:
    53
    Location:
    Alpharetta, GA.
    Not so sure about using mastic - I seem to remember that mastic should not be used in wet areas - I would go with the CBU and thinset.
  16. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    The pros always recommend thinset for wet areas. But there is a mastic ,which must be identified as Type I ,which is certified by the tile council for use in showers. I have used it many times, and prefer it. It has more tack than thinset, which is nice for wall work. And premix is just easier for DIY work.
  17. Tell us if it's a shower too. A tub-shower.

    David
  18. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
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    Location:
    New England
    You have to read the instructions very carefully on any mastic. Some allow use in damp areas, but their definition of damp may not coincide with a shower. They often restrict use to smaller tiles as well.

    Thinset (the real stuff dry, mixed with a liquid) includes a fair amount of cement in it. Cement turns into a hard, insoluable mineral once it cures...once cured, you could leave it underwater and it wouldn't turn to mush.

    Mastic stays spreadable in a plastic bucket because it is not exposed to air and can't dry out (or at least for awhile - watch the sell-by date). Stick it between something like Redgard (a paint on membrane) and a big, impervious porcelain tile, and guess what - it's just like leaving it in a bucket. It can only dry out via the grout lines. It could literally take years to dry out an attain max strength. That's if you don't run the shower on it every day. Grout is not waterproof (well, some epoxy grouts are), and will allow some moisture through.
  19. plumbitup

    plumbitup New Member

    Messages:
    4
    Kerdi works

    Use this product called Kerdi....
  20. Southern Man

    Southern Man DIY Hillbilly

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    530
    Location:
    North Carolina
    Put the tile on the greenboard and sell the building within 5 years. j/k :D
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