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metcarl_gw

areas of dark grout lines in new shower

metcarl
10 years ago

Our shower has just been redone (because of mold/leaking/improper tiling job). It looks beautiful, except that the medium gray grout lines are staying dark. Immediately after showering, most of the grout appears wet. Several hours later and even 4 days later, the are multiple areas where the grout remains dark. They are in different areas - along the edges, some by the drain and others near neither the edge or the drain.

I discussed this with my contractor and tiler who first questioned if we were using the fan. Yes, we are using the fan and leaving it on for hours and days and leaving the shower door open. Then, the tiler came back out and said that the grout is staying wet because of the mud base becoming saturated and remaining wet. As the mud becomes more saturated, the darker areas may even begin to change. He said that when demo-ing some showers that haven't been used in weeks to months that the mud base can still be wet. (yes, but were they supposed to be?)

My main concern is mold becoming a problem. If the tiler's explanation is basically that the grout is never drying out because the mud base remain wet, then won't there be mold problems?

I have been reading the forums and know to ask about adequate preslope (not just slope) and clogged weepholes and what mortar mix was used. I just wanted to make sure that this wasn't an adequate explanation before I proceeded.

Comments (28)

  • metcarl
    Original Author
    10 years ago
    last modified: 9 years ago

    So, the shower has been drying out for 10 days with a humidifier, with no change. There are still some areas of dark grout. However, the lines do not disappear with a hairdryer as well.

    Our contractor has talked to others about this problem and most have had this happen on occasion and they all feel that the job was done correctly (not sure how they know this). They thought that If the mud bed was wet at all, all of the grout lines would be darkened. And that all of the moisture should have been pulled out by the humidifier.

    Not sure where to go from here.

  • metcarl
    Original Author
    10 years ago
    last modified: 9 years ago

    So, the shower has been drying out for 10 days with a humidifier, with no change. There are still some areas of dark grout. However, the lines do not disappear with a hairdryer as well.

    Our contractor has talked to others about this problem and most have had this happen on occasion and they all feel that the job was done correctly (not sure how they know this). They thought that If the mud bed was wet at all, all of the grout lines would be darkened. And that all of the moisture should have been pulled out by the humidifier.

    Not sure where to go from here.

  • enduring
    10 years ago
    last modified: 9 years ago

    Mongoct, now I get it! Great information in your post and the link was very informative too.

  • MongoCT
    10 years ago
    last modified: 9 years ago

    Enduring, thanks.

    metcarl, did you find out if your membrane is flat or sloped?

  • threeapples
    10 years ago

    What ended up happening here? We are having a similar problem in one of our showers?

  • L White
    9 years ago

    I have a similar problem as well! Our builder actually said to scrub the grout twice a week instead of just opening up the area around the drain. We had 3 TCNA experts come in and all say that the water is not draining properly in the pan, so our stone tiles are soaked. Mold and mildew is something I can't stand, so we're not using it until the state/county helps us with the repair.

  • PRO
    Creative Ceramic & Marble/ Bill Vincent
    9 years ago

    Good luck with the state or county, but I WOULD talk to a lawyer if the installer (or builder) isn't willing to back their work. In most states there's a minimum of 5 years the builder has to warranty all aspects of the house, and even the tile installer has to warranty for atleast 2 years. Come to me, and it'll be 25 years, AND backed by the manufacturer, in case I'm not around.

  • hotmae3
    7 years ago

    Hey, we just moved into our newly built home in February. We have two walk-in tiled showers. Some of the grout is already "caving in." We repaired the areas and most have done great but two spots in particular turn grayish/black just hours after we filled them. I cleaned them with oxy clean and dries them with alcohol and a hairdryer before grouting. We have done this twice now and both times they turn black within hours. I can't find anything online about this. Please help!

  • millworkman
    7 years ago

    I would be curious to know how the shower was built and what waterporoofing system was used. Does not sound good, and my first though was mold under the tile, especially since the gout is "caving" as it sounds like an improper tile setting and probably substrate. There will be pros along who know much more than I but they will probably ask the same first two questions.

  • hotmae3
    7 years ago

    This is all I know... It had some kind of black waterproofing plastic like material and was filled with water then inspected to ensure nothing was leaking. This was then filled with a dark brown blackish mud which was shaped into the floor shape needed for proper drainage. The tiles were then placed over this and grouted.

  • hotmae3
    7 years ago

    How fast can mold grow? These are blackish, bluish in a matter of hours.

  • millworkman
    7 years ago

    Not growing I think spreading. You possibly have a factory of mold below your tile.

  • PRO
    Creative Ceramic & Marble/ Bill Vincent
    7 years ago

    That's not mold. Not sure what it is, but it's not mold. I'd have to get a more specific answer on the waterproofing system before I comment further.


  • enduring
    7 years ago

    Wouldn't the "waterproofing plastic like material" need to be sitting on a preslope? If the slope was built above the waterproofing then the plastic pan could be holding water, because it is not sloped to the drain. It is waterproofed but not installed to funnel the water to the drain. Isn't that right Bill?

  • PRO
    Creative Ceramic & Marble/ Bill Vincent
    7 years ago

    Considering the problem, it wouldn't matter. That's not a matter of moisture darkening the grout joints. That's some sort of foreign material, and it takes mold a little bit longer than just a couple of hours to show itself.

  • hotmae3
    7 years ago

    Unfortunately, that's all I know about how it was built. I'm glad you don't think it is mold. It is so weird. We fixed several areas with the same batch of grout and some did great. The ones pictured above looked great too, at first, but then darkened. Our GM is coming out Wesnesday. We will see what he says.

  • hotmae3
    7 years ago

    He didn't have a clue. Guess we will see what the tile guys say.

  • hotmae3
    7 years ago

    Okay, the tile guy came out today. He re-grouted the areas and below is how it looked a couple hours later. He has no idea what is going on and I am going crazy!

  • PRO
    Creative Ceramic & Marble/ Bill Vincent
    7 years ago

    You might have someone from servpro come out and take a look at it. I still don't think it's mold, but it wouldn't hurt to positively rule it out.

  • PRO
    Joseph Corlett, LLC
    7 years ago

    That looks like some sort of contamination in the tile bleeding out. I'd try grinding out the grout and a bit of the tile itself, a thin coat of clear silicone, and regrouting.

  • jellytoast
    7 years ago

    I'd pull those tiles off and see what's going on under there.

  • PRO
    Creative Ceramic & Marble/ Bill Vincent
    7 years ago

    problem with grinding it out is if it's a surface applied waterproofing, you could really pooch the shower unnecessarily.


  • jellytoast
    7 years ago

    From the OP's description, it did not sound like surface applied waterproofing ...

    "It had some kind of black waterproofing plastic like material and was filled with water then inspected to ensure nothing was leaking. This was then filled with a dark brown blackish mud which was shaped into the floor shape needed for proper drainage. The tiles were then placed over this and grouted."

  • Tmnca
    7 years ago

    It looks like pigment may be leeching out of the tiles there - maybe remove grout, paint some kind of sealer on the exposed tile edges and then regrout?

  • enduring
    7 years ago

    I do not believe pigment will ever leech out of ceramic tile. The clay body is just that clay, and will be fired and stable. The color that the tiles are glazed, with is a form of glass melted to a glaze during the firing process, will not bleed either.

  • Rob McNally
    7 years ago

    Any resolution on what's causing the dark lines, or how to address them? I am having a similar issue on a shower wall tile re-grout. Most of the white non-sanded grout came out fine, but in a few spots it appears that "something from below" leached into the white grout causing it to become grey and dark in spots.... and it occured quickly within the first 3- 6 hours that the grout was drying. In a few spots, it became rust color, as if the red ceramic base of the glazed tile was bleeding into the grout. Any thoughts?

  • hotmae3
    7 years ago

    The district manager came out and his thought was that maybe some plumber's glue got dropped and the purple color was soaking through the grout from underneath. The tile guys kept digging it out and re-grouting and finally it looks better - although still dark in some areas. I really have no idea what is going on.