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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  • David.

    My grout on the floor is sanded and keeps on cracking every 4 days how can I find the problem or the reason to why this is happening we just remodel the shower and put tile about a month ago.

    • Roger

      Hi David,

      On the shower floor or the bathroom floor? If you can tell me the method your shower (or bathroom floor) was constructed I can likely give you a good idea of the possible causes.

  • Colin

    yesterday i grouted a new bathroom floor but either i mixed too much water in or used too much on the cleanup as today the grout has cracks in it – for how long can i add more grout or is it already too late and i should remove 2/3?
    thanks

    • Roger

      Hi Colin,

      Is it unsanded grout? Because with sanded grout it would take a virtual shit-ton of water to make it cure with cracks. If it is unsanded, yes, you can go back over it with more. If it is sanded we need to figure out why it’s cracking before proceeding.

  • Rhonda

    Hi Roger,
    I had our MB remodeled 7 months ago and install a flat pebble rock shower floor. Our contractor used an epoxy grout and have found that the grout is wearing away around the shower drain about 1/4″ and in a few spots on the shower floor. Any ideas what is causing this and can I build back up the grout in these areas or do I need to remove the grout around the drain and regrout? Thanks

    • Roger

      Hi Rhonda,

      I do not know what would cause that short of incorrect mixing or installation of the grout. You can go over epoxy grout with new epoxy grout.

  • Donna

    We had our bathroom floor tiled about 15 years ago and the contractor did not remove the baseboards prior. There are some small areas in the commode room where the grout at the perimeter is no longer there. My husband had caulked it but with white caulk on gray grout and it looked unsightly. I’ve removed the caulk and want to know what the best solution is since I’ve read that trying to re-grout over grout doesn’t work. Thank you!

    • Roger

      Hi Donna,

      Since that is a change of plane you’ll need to use caulk or silicone there if you want it to last. Most manufacturers have both in the same grout colors that they sell.

  • Steve

    Hi roger 2 weeks ago I had a large area tiled in my house 60mt but some parts look like grout has not dried it should be light grey but looks dark in places all so not enough grout .will I be able to put in more and do you think tiler never mixed properly and this is why couloir is different . Many thanks Steve .

    • Roger

      Hi Steve,

      It could be a number of reasons, improper mix, too much water used to clean, uneven curing due to temperature or depth, etc. I would not add more grout at this point, it’ll likely just flake off. I would call the contractor and have them remedy the situation, it is an improper installation if you have inconsistent grout color and height.

  • Ken

    Hey Roger, I installed a 1 1/4″ granite floor in my foyer. I haven’t applied the grout yet. I am experimenting with this but didn’t realize that I can’t put grout 1 1/4″ deep. What can I use other than grout? Or can I just layer the grout?

    • Roger

      Hi Ken,

      It depends on how wide your grout lines are. If they are less than 1/4″ you can put it 1 1/4″ deep. No reason at all not to.

  • Sean

    Hi Roger,
    My question is about cracking grout in the corner of our mstr shower. The walls are both exterior in this corner and I am seeing a small crack almost floor to ceiling. I’m guessing this is due to either expansion/contraction of this south facing wall or shrinking of the building materials. Either way I need to address the crack. The tile setter used Kerapoxy mortar and grout. Do I need to follow the 2/3’s rule outlined above, or do I need to do something different in this area. I’m also noticing this happen in our kitchen with the same product on the same wall. I’m hoping not to get into the silicone area as that means lots of repetitive future work. Your advice is greatly appreciated.
    Very respectfully,
    Sean

    • Roger

      Hi Sean,

      Unfortunately any change of plane requires either caulk or silicone. The planes of those walls move in different directions, grout will never last, silicone can compensate for the movement.

      • Sean

        Roger,
        Thank you very much for the reply.
        So if that is the best solution then it is what it is. So we have colored grout there now in a Pewter color, will there be silicone or caulk (is one better than the other) available to match that color (or get as close as possible), and lastly do I need to dig out the existing grout before I silicone these areas?
        I do appreciate your time

        Sean

        • Roger

          Every grout manufacturer makes a matching silicone or caulk for their grout. Silicone is better, it lasts longer before losing elasticity and needing to be replaced. Yes, you need to remover the existing grout.

          • Sean

            Thanks again for the advice, I do appreciate your expertise and guidance.
            Sean

  • Marie Delaporte

    Hello Roger,
    We just grouted our shower walls less than 15h ago, some places still need to be built up, can we apply new grout to the dump grout from last night ?

    Or do we need to remove the grout to at least 2/3 the depth of the tile and regrout it all ?

    Thanks SO much in advance.

    • Roger

      Hi Marie,

      You can still add more grout to it for the next couple of days if you need to.

  • Robert

    Rodger,
    I’m repairing a shower floor and wall that have had caulking installed in the base and both end corners. Mold is starting to grow. What is the best way to remove the caulking from ceramic tile. So the grout will bond to the tile.I plan on regrouting.

    • Roger

      Hi Robert,

      A razor knife is the best method, followed by a razor scraper. If it is the corners you are speaking of, they should have silicone in them, not grout. It is intended to be a regular maintenance issue, replacing the silicone every 5-7 years. If you grout that the grout will crack.

  • brad

    our contractor didn’t mix all the bag of white grout together so we have some spots where the grout looks yellowish and not white. Can we just put a new grout mix over the existing ? grout is probably six months old now.

    • brad

      this was for a shower wall

    • Roger

      Hi Brad,

      I wouldn’t recommend it. It’ll likely begin flaking off fairly quickly. You need to remove the existing grout down to 2/3 the depth of the tile, then regrout it.

  • Jennifer Bailey

    I recently (2 weeks ) had my bathroom , floor and shower , tiled. It looks like some of the mortar rose into the grout lines. The mortar is dark gray and the grout is light gray. It is very obvious and in places on the floor that is seen. How can I fix this problem ?
    Thank you so very much !

    • Roger

      Hi Jennifer,

      You need to remove the grout and thinset in those areas down to at least 2/3 the depth of the tile and regrout it.

  • Tina

    Can I grout over new grout that hasn’t been sealed yet (because some places still need to be built up)?
    Do I need to wet the grout around the place I scraped out before I put new grout in?

    • Roger

      Hi Tina,

      Yes, provided it is new grout. You want the existing grout damp, but not wet. And you don’t want the sides of the tile wet.

  • Debbie Cummings

    I have already tiled, grouted and sealed my new shower floor with 2 in squares. The shower has not been in use yet as we are waiting on the glass. While testing the new shower heads, we have noticed that water will puddle on the shower floor. Even 10 hours later they have not dried. I have noticed that the grout on the floor is not high enough, I guess I wiped off to much. This is my first tiling attempt. Can I add more grout on top ? Or do I need to remove some before I add?

    • Roger

      Hi Debbie,

      Do you mean it puddles in the grout lines? If so then yes, you should still be able to add grout to it and not wipe so much out as cleaning. If you mean it puddles in, like, a puddle, then do you have a low area in your shower floor? Like a birdbath?

  • Tom Thesing

    Hi Roger, I am currenty remodeling my family room, and am just about finished, appr. 15 yrs ago I installed 12×12 stone like tile and used grey sand grout, and grout sealer, after living with the room for awhile I realized I troweled too much grout out of the joints when I did the installation, which makes it hard to sweep the floor successfully. So if possible I would like to top off the grout joints to raise the elevation of the grout joints and possibly use a protective sealer if You recommend it? please let me know if these request are possible and best methods to preform the work.

    Thanks Tom (Cincinnati Ohio)

    • Roger

      Hi Tom,

      Unfortunately with grout that old you’ll need to remove all the existing grout (up to at least 2/3 the depth of the tile), then regrout the entire thing. If you fill over the old stuff the new grout will likely begin flaking off within a month.

  • Chance Studer

    Hi, I grouted part of my shower a couple weeks ago and I’m ready to grout the rest. Can I just butt the new grout against the old grout or will it leak where they butt up?

    • Roger

      Hi Chance,

      Yes, you can go right against the existing. However, grout has absolutely nothing to do with whether or not it will leak, your substrate needs to be waterproof.

  • Michael

    Hey Roger,
    I recently put down vinyl tile in my kitchen over top of old wood floors that had large gaping gaps between the slats. The sticky Vinyl tile was placed with 1/8″ grout lines. I then grouted it. about 2 weeks later the grout started coming up in high traffic areas. Chipping and chunks we’re getting dispersed. I imagine this is due to poor mixing. Do you recommend I chip out most of the old grout like you said in your post or does the fact that it’s vinyl tile change anything? the vinyl tile is about 1/8″ thick. Thanks, MIke

    • Roger

      Hi Michael,

      The problem has nothing to do with the grout and everything to do with your substrate. You need a layer of regular plywood over those slats. They move independently, when they do that beneath your vinyl it causes the grout to come out.

  • Jen

    Hi there,
    I bought a new condo and it’s less than a year old. The entire building is. I noticed that in the shower stall the corner grout, from tub to ceiling, is cracked but I’ve been told it’s likely due to a new house settling. But what do I do? I have no idea how they tiled the bathroom, what materials they used or type of grout. Should I have a professional look at it? And if so what exact kind? In addition, what are the ramifications if I don’t get it fixed? New homeowner here, and totally clueless. Thanks!

    • Roger

      Hi Jen,

      Provided your substrate is waterproof (it should be) then you have nothing to worry about. The grout in the corner, however, should be silicone instead of grout. Silicone can compensate for movement whereas grout can not. You just need to scrape the grout out of that corner and replace it with silicone.

  • Kathy

    Hi, I just grouted the tile on my hearth with pre colored sanded grout. It is my first time to grout, and once I was done I saw on one time I didn’t get enough grout into the joint so there is a lip. Can I just mix and add more grout to that small area? I have not sealed it yet. The grout is dry though. Thank you for your help!

    • Roger

      Hi Kathy,

      Yes you can.

  • Jane

    Hi, i had my kitchen tiled with a 60x60cm porcelain tile. Its been a week now and i feel like the grout lines are too deep…is it possible to just regrout the entire floor without removing the existing grout? Its only a week old.

    • Roger

      Hi Jane,

      Yes.

      • Amanda

        I have same problem. Does it matter,what kind of grout was used? Or u can go over any kind with the same kind? As long as its within 28 days? And do u have to wet the grout before going over it again?

  • Artie

    Hi Roger,
    my kitchen tile floor was installed a few weeks ago and the installer did not use enough mastic in some areas and the tiles are moving in some of the corners causing the grout to crack. the kitchen cabinets have been installed on top of the tiles, so removing all the tiles is not possible. any reccomendations?

    • Roger

      HI Artie,

      Yes, replace the floor. If it was installed with mastic you’re going to have a lot of issues with it.

  • Kate

    Hi Roger,

    I just had my bathroom renovated. It’s a shower/tub combo with an acrylic tub. The grout looked fine until the first time I took a bath a noticed small little fractures where the tub meets the wall. My contractor said this is because of flexing when the acrylic tub is filled versus empty but he added clear silicone over the grout.

    I’ve only ever had porcelain tubs before so no flexing. Is my contractor right or is he lying?

    Thank you.

    • Roger

      Hi Kate,

      He’s correct about the cause, but not the solution. There will still be cracking grout there, just held in the gap by the silicone. You’ll still see it. The entire gap should be siliconed – no grout.

  • Conner

    Hi Roger,
    I just grouted my tile last night and am noticing a few voids here and there. Whats the chance i can just throw a little color match caulk in there?

    • Roger

      Hi Conner,

      The chance of you being able to do it is 100% (I assume), the chance that it will match well enough not to be notices is about 20%. It would be better to go over those areas with some more grout.

  • Scott

    After tiling a bathroom wall I noticed I didn’t get all the thinset cleaned from the grout lines before I put in the grout can I just regrout or will it need to be removed first

    • Roger

      Hi Scott,

      It needs to be scraped out of there first.

  • Nancy Jacobs

    We have just installed a very expensive shower with lovely tile. The job is about 4-5 months old at most. We now notice “sand” like substance coming off when we wipe our fingers along a grout line. Also, in the cutout where the soap & shampoo go, the grout is actually rolling off, sort of like silly putty.
    The shower floor (different tile) has a very small section which has “sunk” to about 1/4 inch. Any ideas what this is all about. The installer has a good recommendation. Thanks for any help.

    • Roger

      Hi Nancy,

      What specific brand and type of grout did he use? Do you know?

  • Lizzy

    Hi, Roger – Our shower floor is tiled with small squares that appear to be connected with plastic so that it’s like a grid. The grout between the tiles has worn away in some areas. In reading your instructions and your responses to questions posted, it appears that removal of the old grout is important before regrouting. My question is this: what is the best way to remove old grout when there are these plastic connectors between the tiles?
    Thanks for any help!

    • Roger

      Hi Lizzy,

      Same way you would without the connectors. Just get as much out of there as you can, don’t worry about destroying those connectors, they are only there to hold the sheets together before it is installed. Once installed they are useless and serve no purpose.

      • Lizzy

        Thank you for your speedy reply, and for your advice. I’m grateful!