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  • mapei premium grout question.

    Hi all, about 6 months ago I built a tile shower with a built in wall shelf about 16" from the floor. I used mapei premium grout that says "for use on shower walls and floors and also says in bold, "DO NOT SEAL". I have now noticed that the grout line on the front of the shelf has expanded and caused the grout to crack and break away. once I removed all the grout from the affected area (everything below the shelf) I found water seeping out of the cleared out grout line. I am going to let it dry and then re-grout what I removed, and my question is should I go ahead and seal all the grout lines even though the container says not to?
    Thanks in advance,

  • #2
    Re: mapei premium grout question.

    I would contact Mapei's local rep. I haven't used Mapei, but in my experience the tile industry suppliers will often help out with free material, and sometimes failure analysis or at least advice if their stuff is behaving badly. It's worth a phone call. Hope you put a good waterproof membrane in when you did the work. 6 mil plastic behind the backer board is a common way to do it, but I like Kerdi over plain white sheetrock. Done right, it's totally waterproof and you don't soak the backerboard.

    I started using the Laticrete Spectra Lock epoxy grout and like it, even though it's pricey. With some tiles, it's a ton of work to get the residue off the tile, with others, it seems to wipe off nearly effortlessly. But after you get past the installation, the grout itself is very good.
    Last edited by Andy_M; 06-29-2011, 01:03 AM.


    • #3
      Re: mapei premium grout question.

      If you decide to seal the grout, either nothing will happen, or the grout will get angry and do something like change colors, or weaken/crack/fall out, curse at you, who knows. I second the suggestion of contacting the rep and seeing what they have to say about sealing the grout. I would also monitor the area that cracked, you may need to use a sanded grout caulk if the joint cracks again.
      We don't have preventative maintenance around here, we have CRISIS MANAGEMENT!


      • #4
        Re: mapei premium grout question.

        How did you waterproof under the tile ( the walls & floor) ? Mapei premium grout is a pre-mixed grout. Pre-mixed grouts & mastics should not be used in a shower. I would cut in to the other side of the wall to see if you have a mold problem. If you waterproofed correctly & there is no mold under the tile I would get a multi-tool & a grout blade, remove all the grout & re-grout with an epoxy grout. Make sure you have plenty of help & do a test spot if you use epoxy grout, because it is not user friendly, but it works great. I use it all the time, but I know how it works. If you have a mold problem or the underside is not correctly waterproofed. I would remove everything put up hardi board & use a kerdi shower system. Everything is one kit that you will need except thinset to make a waterproof shower.


        • #5
          Re: mapei premium grout question.

          My first question is what waterproof membrane did you use on the shelf. It sounds as if your getting moisture build up under the tile and grout which in turn is causing the grout to expand/contract to much when you use the shower.

          Personally I don't care what the bag or can says, I doubt there is truly any grout on the market that is 100% water tight. I have done several Schluter and Weidi trainings over the years and one of the first things they teach you is to not believe manufactures claims when it comes to water proofing.