When there is a significant amount of movement on the substrate of a tiled floor or wall it may lead to grout cracking. When this happens it will leave what looks like a crack in the grout where it has come away from the tile. Unless your grout was installed very recently this is always due to movement in the tile. If your grout is new it may be caused by incorrectly mixed grout. With grout that has been doing this for a while it may lead to whole chunks of grout coming loose and leaving large voids in your grout lines.

While it may be tempting to simply mix up some more grout and fill these voids you need to know that it will not last. If you do this it will fill the grout lines just like new but over time will lead to the same problem. Grout over grout is not a permanent solution.

Why it won’t last

The first reason is that when you go over the top of grout that is already cured with new grout, there is no adhesion to the old grout. It will instead simply create a layer of grout on top of the old grout. These layers have no way of  sticking to each other. When you grout tile the grout actually sticks to the sides of the tile rather than whatever substrate is beneath it. While it will stick to the substrate at the bottom of the grout lines to an extent, it is not a permanent bond. Attempting to grout over the top of old grout is simply stacking two seperate layers of grout. It will always remain two seperate layers.

The second reason is no matter how much of the old grout you may take out to install new, if you do not fix the actual reason the grout failed in the first place, eventually the same thing will happen again. As with any problem you may encounter with a tile installation, you must figure out the initial cause and fix it to prevent repeated problems. This is an involved process which I will cover in a different article. For now I’ll stick with the solution for the grout problem.

What to do

Rather than simply filling the grout line where the grout is missing, you must remove the old grout at least 2/3 the depth of the tile so the new grout has a feasible surface to grab onto. The easiest way to do this is with a grout saw. Ideally you would remove the old grout all the way to the substrate before regrouting it, but 2/3 will be sufficient if it is difficult to remove.

You need to remove any of the old grout that seems loose or has come loose from the sides of the tile. You also need to make sure the spot where the new grout butts against the old is a 90 degree angle, or close to it. In other words from the top of the grout line straight down. You do not want a slope. Eventually a slope must be feathered to a very thin edge. That will be the first place it will fail again, any very thin layer. A 90 degree angle prevents that.

It is also better to make the transition from old grout to new in the middle of a grout line rather than at one of the corners of the tile. The grout line at the corner of the tile has six different spots it can fail, the middle of a grout line has only one. It lessens the chance of failure.

After you remove the sufficient amount of the old grout just mix some new grout and fill the lines. You must make sure you force the new grout into the grout lines very well. You want to make certain there are no voids and the lines are full.

The above method will work to temporarily fix your cracking grout. As I pointed out above, you must find the initial reason for the grout failure before a permanent fix will last. It’s difficult to say how long this fix will work, it may be two weeks, it may last a year. That depends on the severity of the problem that caused it. It also depends on the application (wall or floor) and how much use it gets. A floor in your main entryway will not last as long as a shower that is never used.

You should also take into consideration the age of the grout. If you are repairing grout that has been installed for five years, the new grout, even if it is the same brand and color, will not likely match perfectly. The best solution, of course, would be to fix the cause of the cracking and regrout the entire floor. Depending on what you’re fixing and why this method may solve your problem.

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Leave a Comment

  • Diane

    Hello and thanks for taking my concern😊my floor tile was done 3 weeks ago. I need more grout added to the grout lines. Also, when they washed the floor when they were finished, they left like towel marks on the tile itself. I used plain water for cleaning the floor. Still has pattern on the tile as to where they wiped the floor after words. They dragged a large wet towel across floor

    Reply
    • Roger

      Hi Diane,

      I would contact your installer and let him know about your concerns. If the grout lines are not full enough that is something he will have to do. You can likely get the wipe marks off with a little dawn dishwashing soap and warm water, depending on the type of tile (provided it wasn’t epoxy grout).

      Reply
  • Stephanie Fleming

    Grout is cracking around a window in shower. I want to replace grout with ceramic tile caulk. Do I need to remove all grout before applying caulk ? Or can I remove loose grout and then use caulk?
    Thank you so much! I obviously hired the wrong contractor for this job!

    Reply
    • Roger

      Hi Staphanie,

      You’ll need to remove all the grout first. Whether it’s loose now or not, it eventually will be. If that’s behind silicone it will debond the silicone.

      Reply
  • Timothy CK

    I recently installed a backsplash with 1/4″ thick stone tile with 3/8″ spaces between each tile. I used a premixed grout as I didn’t need that much. After 48 hours I applied a liquid sealer and noticed cracks throughout. I didn’t think if was that big of a deal , but now I am thinking it is. It will be about a week out before I can get to it again. Can/should I just apply more grout? Thanks

    Reply
    • Roger

      Hi Timothy,

      With premixed grout it WILL shrink as it cures, and 3/8″ grout lines are huge. It’s likely just due to the shrinking during cure. Yes, you can just go over it again with more grout.

      Reply
  • Kathy

    I installed a mosaic tile in a shower floor. I used the shower kit for the floor under the tiles and applied my tiles on top of membrane just as the instructions stated. After using the shower the grout was cracking and chipping out. Some of the mortar seeped up through the grout after it started to crack out. I tried fixing and replacing the grout. I waited 3 weeks before using the shower again. The grout cracked out again. I need help in fixing this issue. It would be too much work to remove all the mosaic tile and I would probably damage the membrane below. What can I do to fix this issue. It appears to only be doing this in the area the water hits from the shower head and where we stand in the shower. Help!!!

    Reply
    • Roger

      Hi Kathy,

      What ‘shower kit’ did you use? It’s difficult to answer that accurately unless I know the specific shower pan you installed.

      Cracking grout is indicative of movement in the substrate beneath your tile – either the bond of the membrane to the pan or the bond of the pan to the substrate. Water is not causing the issue.

      Reply
      • Kathy

        I used a kit that I purchased from Menards. I can’t remember the exact name but it had a pre formed hard stroaform base and a red waterproof membrane that was applied on the top.

        Reply
        • Roger

          And how was the shower base installed? Did you have thinset beneath the shower pan as you installed it? And is the waterproofing membrane a liquid or was it a waterproof sheet?

          Reply
          • Kathy

            Yes thin set under pan and on top of pan. Then sheet membrane installed over that. It was like a really thick paper of some kind.

            Reply
            • Roger

              That is the redgard shower kit. If you have cracking grout in the shower base tile then you likely have a bonding problem somewhere. Biggest cause is the pan not being bonded properly to the substrate. The other two causes may be the membrane not being bonded to the foam on the pan or the tile not being bonded to the membrane.

              Causes for that may be thinset being mixed incorrectly, Spreading the thinset and letting it set too long or simply not embedding whatever you’re attempting to bond into the thinset correctly. Movement of some sort is causing your cracking grout.

              Reply
  • Austen Rose Thompson

    I had a contractor install marble mosaic floor tile (small) and he unfortunately wiped out too much of the grout. He then walked off the job and it’s been sitting unused for a year. I cannot rip out the entire floor and the grout lines would take decades to scrape out since it’s mosaic tile. I want to add more grout but I hear that’s bad. I need all the help I can get. Is my only option living with it or ripping out the entire floor?

    Reply
    • Roger

      Hi Art,

      You can not use regular cementitious grout on it. You’ll need to have it grouted with either epoxy or a urethane-based grout. Either one should work to fill what you have. Ideally you would get it in the same color it is currently grouted (same manufacturer).

      Reply
      • Austen Rose Thompson

        Thank you so much! I’ll look into it.

        Reply
  • Lori

    My contractor had the walls painted in our bathroom addition during the time we were waiting for the tile to cure before sealing. The painter got blue paint and dirty water on our brand new white unsealed grout. I had asked the tiler to use an additive for extra stain protection and it appears that he didn’t. He used un-sanded grout with water. Some of the grout will need dug out but some can stay as is. It was grouted 10 days ago. We had been waiting for the epoxy shower floor to cure before sealing the entire shower all at the same time. I want him to go over the entire shower with another coat of grout. Can I have him use the additive this time, or will it not adhere to the grout that was done using water?

    Reply
    • Roger

      Hi Lori,

      Sorry for the delay – website issues. You do not really want him to mix up the new stuff any differently than the old, it may look different.

      Reply
  • Tom

    I put grout on a place stone shower floor today. It’s sands grout with some pretty big grout gaps. I cleaned to much grout from them and I also see my thin set poking through in some places.
    Can I just clean those spots out and regrout the whole floor?

    Reply
    • Roger

      Hi Tom,

      Normally yes.

      Reply
  • Heggy Gonzalez

    Hi roger my tile guy just grouted today and there are a bunch of holes is the grout. Reading through your posts it sounds like I can just go over it again since it has only been a day?

    Reply
    • Heggy Gonzalez

      Here Are some pictures plus I thought it would be a lot darker can I stain it or just go over with a darker grout?

      Reply
      • Roger

        Going over it with a darker grout will not work, you’ll see both colors. You can stain it if you want, but you’ll need to wait at least 28 days for a full cure.

        Reply
    • Roger

      Hi Heggy,

      Yes, you can. But I’d make him do it, you know, since you’re paying him to do it correctly and everything… :D

      Reply
  • Kevin Stock

    Hi Roger. Four days ago, my contractor grouted my new floors, but washed away too much of the grout. Is it too late to just add another layer to make it more flush with the tile? Btw, the day after it was done, I asked the contractor if it can be done, and he said no, that the grout was already rock hard. Thank you.

    Reply
    • Roger

      Hi Kevin,

      Anytime up to 28 days when the cement crystals are fully hydrated.

      Reply
      • Kevin Stock

        Wow! Thanks Roger. I thought the window for adding more sanded grout was only 2-3 days. Shall I tell my contractor he has just under a month to add another coat of grout? That would be much preferable than trying to take it all out. The lines are 1/16″ so I was told it would be next to impossible to remove the grout without damaging the glazed porcelain tile. Thanks again!

        Reply
        • Kevin Stock

          Oh ya, yes I said he used sanded grout on 1/16″ grooves. Even the bag says it’s for 1/8″ or wider. It feels not only too deep (washed out) but also very coarse. The grooves are a complete dust trap. I used black grout, but it looks like I used white because of the dust! Should he have used non-sanded grout or is he ok to choose whatever he’s comfortable with? On the day of grouting, I suggested non-sanded grout and he said no.

          Reply
          • Roger

            I always use sanded grout on 1/8″ and 1/16″ grout lines. But I know how to do it correctly, he doesn’t seem to.

            Reply
        • Kevin Stock

          Here are a couple of photos. I repeatedly asked for high grout lines in order to achieve a unified, almost poured concrete look. The tiles are beautiful and they were laid well, but the grouting was clearly an afterthought. The contractor is willing to do another coat, but he says it’ll probably chip off. He asked me to research what coating I’d like to put on top. I was thinking maybe epoxy grout, since it’s like plastic and tends not to chip. What would you do if you were me?

          Reply
          • Kevin Stock

            This one shows the black grout looking white.

            Reply
          • Roger

            He used WAY too much water when cleaning the grout.

            Reply
        • Roger

          You should tell your contractor to get in there now and fix his screw up. :D

          Reply
          • Kevin Stock

            Thanks so much Roger! The tiler recently discussed with the contractor the possibility putting on one more layer of grout, but this time using non-sanded. He said he can’t guarantee it will not chip off, though. What I would like them to do is fix the situation in a way that will not void my warranty. I don’t care how they do it as long as they’re willing to stand by their work. If a second layer of something chips off, I need them to come back in and try something else. Their position is that it’s not an option to remove the grout and start again because that process will chip the tiles. He said he’s not willing to take that chance. Do you think it’s possible to remove the grout so they can start over? Or do you think they should just add another layer of unsanded? How about a layer of epoxy grout? I heard it’s super strong and smooth. They just think I’m being fussy and unrealistic in my expectations. But I don’t think so. I’ve made it very crystal clear on multiple occasions prior to the grouting that I wanted a seamless, unified look to the floor with high grout lines. I don’t like it that even when I sweep the floors, my black grout lines look white. I don’t want to have to mop the floors or vacuum the grout lines in order to make the lines look black. Your help in this has been invaluable. Thanks again!

            Reply
            • Roger

              The unsanded may last, depending on the cause of the problem. If it’s simply low grout lines it should be fine, if there’s movement in the substrate it won’t last. Unsanded is a better option than epoxy in this situation. The epoxy will bond tenaciously to the sides of the tile, not so much to the existing grout. Being that there is currently more grout area than tile area to bond to the epoxy will likely not work well.

              Grout can absolutely be removed without chipping the tiles if it’s done correctly by someone who knows how. If he said that – he apparently doesn’t have anyone who knows how. If they’re willing to stand behind the unsanded option I would let them give that a go.

              Reply
              • Kevin Stock

                Thanks again, Roger. You’ve been invaluable in this process. I’ve attached a photo I sent to the contractor and sub-contractor that indicates the kind of seamless effect I was looking for. I was surprised to recently notice that it is, in fact, impossible to clean my grout lines enough to make them look black. They always look white. It seems that not only was too much grout washed off, but the dark colour was washed out as well. Thanks again!

                Reply
      • Jeanne-Marie Lovell

        I just grouted using polymer-enhanced sanded grout, but the tiling job we laid is kind of uneven. It was really hard to get the grout as deep as I wanted it. But you say I can lay more on top within 28 days?! It’s been less than 24 hours. Should I go for adding more? My only previous experience is making small mosaics.

        Reply
        • Roger

          Hi Jeanne,

          Sometimes it works, sometimes it doesn’t. It depends on a lot of factors. Give it a shot, worse case you’ll need to dig it out and do it again anyway.

          Reply
  • Jamie

    I just did one layer of grey grout to my backsplash with the new trend of grey color….I hate it.

    Can I just go over the grey grout with white? Or do I have to grout saw it? Will this ruin my new subway tile??

    Thanks!

    Reply
    • Roger

      Hi Jamie,

      You can, but it won’t be white, the gray will show through in areas and it will likely flake off over time. You need to remove the gray. No, it won’t ruin your subway tile.

      Stop following trends. :D

      Reply
  • Christina

    Hi,
    I need some help. My husband and I just paid a lot of money to have a flooring company lay wood plank tile through out our downstairs (1200 sq ft). Needless to say they did an awful job and I’ve basically fired them. The tile isn’t completely level at the grout lines, there are holes in the grout where there were probably bubbles while they were grouting, and the grout lines aren’t the same sizes – plus some of the grout is sitting on top of our tile. In some areas I can still see the side of the tile itself and to make it worse I ordered brown grout to match the tiles and they put down gray. Now its on us to fix this mess.

    Besides tearing it up and redoing the tile – do I need to drill out all the current grout lines before i regrout the tile? The floors have only been down for about 2 1/2 weeks so its still new. Any advice you have is greatly appreciated.

    Thank you

    Christina

    Reply
    • Roger

      Hi Christina,

      If it is over about three days old you should scrape out the existing grout before filling it with more grout. Grout bonds to the sides of the tile, not the substrate beneath it, which means it has trouble bonding to existing grout and remaining stable. You can try to grout over it, but I’m afraid it will begin to sheer off after a couple of weeks.

      Reply
  • Andrea

    Hi Roger,

    Our 1953 casita was remodeled with 12 x 24″ tiles through the 700 sq ft. The LR is on cement, but the bedroom was on a subfloor (after we ripped off the carpet and then the old, laminate, original tiles). The tile was installed, looked great, but nobody stayed there as it took awhile to pick out new furniture.

    After a few months, someone stayed there for two weeks and two of the tiles had cracked grout around them. That is when I asked the contractor to come over and they said that there is movement. When you stand shoulder width apart and shift your weight you can feel the floor move. We have cracked grout on a few tiles. The tile guy said he’d re-grout and if it happened again, he’d come back. As you predicted it has broken down again and looks like crap…and the tile guy is ignoring my calls.

    It sounds like you’re saying that I have to rip it up and retile! That’s the only option? Ugh! This tile wasn’t cheap. Maybe I’ll have to carpet the whole bedroom to cover up the crappy tile job instead. Hugely disappointed! How about a grout that has rubber in it? A malleable grout? Something else besides “rip it up”?

    Reply
    • Roger

      Hi Andrea,

      Sorry, no such animal. Unfortunately that is the only long-term solution.

      Reply
  • Josh

    I grouted a river rock shower floor 2 1/2 weeks ago. I haven’t done anything with it since as I have been waiting for the shower door to arrive. I have noticed that there are a couple of areas where I wiped too much grout out, causing low spots. Is it too late to just add additional grout over the top? If not, how do you suggest doing it? Just the low spot or the low spot and surrounding area for it to blend better?

    Reply
    • Roger

      Hi Josh,

      You should be able to go over it just fine. Do the low spot and a portion of the surrounding area to blend it.

      Reply