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Thread: Last row of tile above shower base

  1. #1
    DIY Member MarkHash's Avatar
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    Default Last row of tile above shower base

    I have a single threshold rectangular shower base with the tile-lip on three sides. I have done this once before and have had great results except for the silicon caulking instead of the tile grout I used per advise from base manufacturer. It of course turned grey than black and has been an eyesore for years despite the rigorous cleaning it receives once a week. Would a grout with an extreme flexible admixture be a solution rather than caulking where the two dissimilar materials meet, or is there a more mold resistance substance I could use? I have been considering just leaving it bare and just letting it breath also since there will be cement backer board flush with the tile lip anyway.

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Go over to www.schluter.com and look at their Dilex line. This is a tile-in expansion joint that will allow you to eliminate the grout in that area, and there is a different one that can be used in the corners so you'll have no grout in the shower at all, at least for those junctions.

    Prior to installing the cbu, you should run a vapor barrier down the walls and overlap it onto the tiling flange of the pan. there are several alternatives, too. RedGard by www.custombuildingproducts.com is a paint on surface waterproofing material or Kerdi by www.schluter.com is a waterproofing membrane (sort of like wallpaper, but waterproof) that would keep moisture out of the backing. Putting waterproofing immediately under the tile has great advantages since there is so much less to dry out inbetween showers.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Member MarkHash's Avatar
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    Wow....great answer. Similar to a flashing problem I am dealing with on the outside right now......great solution, and it looks like the big orange retailer near me is a dealer. Thanks!

  4. #4
    Homeowner geniescience's Avatar
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    100% silicone, not siliconized latex caulking, is the right stuff to use, in case you are willing to try that first before retiling.

    GE 2000 is one of these 100% silicone products.


    david

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    HD can order the stuff, but you may have to tell them they can! They do stock some profiles, but I don't think they stock the Dilex line. You may have better luck at a local tile store or on-line. One place that has good service is www.tileexperts.com (if the link doesn't work, google them) at a lower price. Shipping can be messy unless you can use shorter pieces, since those trims come in 2.5M lengths (about 8'), and you pay a premium for pieces that long while shipping, not because they weigh much, but the shape. If you can use shorter lengths, they can cut them prior to packaging for shipment and save you some money that way.

    There is an ongoing discussion in the industry about how to best finish the joint at the bottom of the wall. Understanding that grout nor tile is ever 100% waterproof, some moisture will get behind it (not much, but if it can't escape, it can accumulate). How to allow it to escape is the problem. 100% silicon is essentially waterproof and can act like a dam for any that might try to accumulate behind the surface. This is one reason why I like the surface membranes, in the process of waterproofing the backing (cbu, or other material), it limits water penetration to the thinset immediately behind the tile and maybe the tile and grout itself, rather than the entire thickness of the cbu. thus, any moisture that does get in, can't go far, and is more likely to evaporate and not accumulate.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6

    Default how to correct without tearing out

    We have the same problem with black mold in the joint where the tiled side wals meet the tiled floor. I'm fairly sure the guy used 100% silicone on that joint. What can we do to eliminate this? Using a barrier behind the tile is obviously no longer an option for us.
    We're going to replace another shower and I want to go back with tile, but my bride says no dice until we figure how to get rid of the existing problem we have. Help!

  7. #7
    Retired Defense Industry Engineer jadnashua's Avatar
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    The shower may not be constructed per codes. It is wrong, but not uncommon to put the waterproof layer flat on the floor, then build up the pan for tile. By code, the waterproof layer must be installed on a slope (and the tile ISN'T the waterproof layer). If yours is constructed that way, over the years, the pan will retain moisture, and it is really hard to get rid of. Mold needs moisture and food. killing the mold then sealing the grout might help, but grout sealant isn't waterproof, either.

    IMHO, a new shower built with a surface membrane, such as Kerdi from www.schluter.com puts a waterproof layer right under the tile all over, including the pan. Therefore, there's little underneath that can absorb moisture (i.e., no deckmud on the floor or cbu in the walls), so it dries out much quicker and is easier to maintain. If you tile with a good porcelain tile (which has typically much less than a 1% absorbtion rate), it's pretty bulletproof. Then, if you use an epoxy grout and the corner details (expansion joints) from schluter, there'd be NO caulk in the shower to get funky, either.

    Try wiping the shower down after use, and running the vent fan during and after the shower to help dry things out. No moisture, no mold. A mix of water and bleach will help kill it. Then, you must keep extraneous soap scum and crud off, so a good cleaning doesn't hurt periodically. That kills the two things easiest to manage - food and moisture.
    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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