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.
I replaced a section of marble tile in my bathroom. I removed 18/24 inches and put in new backing and adhered the new tile, them grouted the same day. Grout has cracked in several places in the first 24 hours. Can I add grout to this? Thanks
Hey Will,
You can, but I don’t know if it will last. I’m not sure whether or not you have the new substrate tied into the old but it needs to be. Independent movement will crack the grout. It could be just the grout shrinking, though, did you use unsanded grout?
Hi
I bought a house and the kitchen has a glass tiled back splash, but the tiles look cloudy and not shiny, i noticed that when they grouted they didn’t completely wash off the residue, how can i get that off the tiles to make them look the way its supposed to?
Hi Brittany,
A very damp cotton, or even better – microfiber towel should take it right off of glass.
Roger,
I just had my entire first floor tiled. The kitchen was done in slate and from the end result, it’s obvious the installers did not have a clue how to install slate. Initially they were going to keep the tiles very close together and therefore asked me to buy non-sanded grout. Once they began install, they determined they needed a larger grout line in order to work with the unevenness of the slate tiles. But they still went ahead and used the non-sanded grout. When they grouted the floor, they did not clean the grout off very well and now there is grout all over the tiles. I’m using a product called Blaze to try to clean each individual tile so that I can eventually seal this floor when it’s cleaned up. Also, there are so many places that the grout does not fully fill the space between tiles, it’s low or you can see a place where it was just missed. I am going to have to fill this all in with more grout. It’s just a mess and what was to be a paid installation has now become a DIY fix it.
Can I clean all the tiles, then mix more non-sanded grout, use a grout bag and tuck pointer to fill in the missing grout, clean again. Let cure for 72+ hours and then seal it? I have never grouted anything in my life, but I feel like I’ll be more diligent than those I paid to do this job. Can you give me any advice on this mess?
Thanks so much,
Diana
Hi Diana,
If you can get the surface clean, yes you can add more non-sanded grout to fix it.
If you’ve paid for this then you should attempt to get some sort of compensation for this mess. Every county of which I’m aware has minimum amount of time which the contractor must warranty his work. What you’ve described absolutely falls within unacceptable construction practices. You may not feel like bothering with it, but it’s definitely an option.
Hello Roger-
I recently had a ceramic tile shower installed.The “bench” in the corner of the shower has grout lines that are cracking. The tile actually moves if you
press on it. Can you tell me the probable cause and exactly what can be done to fix it?
Thanks,
Mari
Hi Mari,
Cracking grout is indicative of swelling, which is caused by water penetration where water should not be penetrating. Water is getting back in there due to either incorrect or non-existent waterproofing on the bench. You’ll likely need to remove all the tile and probably all the substrate covering the bench frame, determine how water penetrated it, repair any swollen or wet framing, reinstall and waterproof the substrate and reinstall the tile.
Hi Roger,
I bought a home built in 1957 that has the original tile work in the bathrooms. It’s such lovely work I’m trying to keep it. The master shower has a partial glass block wall for the back side. I had to have the bottom quarter or so of the walls and the floor replaced because it had leaked and the previous owners did a horrendous job fixing it. Lucky I did because it was wet underneath the tile when we tore it apart because they didn’t fix it properly. In any case, the grout between the glass blocks had mildewed. My contractor said it was dead so he sealed over it when he did the rest of the grout. It’s rather ugly and I was wondering if I could scrape some of it out and add new grout or if that’s kind of chancy and to leave well enough alone. My contractor said the weak point is where the glass block meets the tile, that that’s where it could leak because it’s difficult to get a good seal between the two different materials. Just wanted to get your opinion. Thanks.
Hi Paula,
The weak spot in any tile installation is in the substrate itself, not anywhere one material meets another. Your substrate should be completely waterproofed, that is the only thing able to leak. You can scrape the grout out and redo it if you want to. No amount of grout or sealer is going to waterproof it so you won’t hurt anything. The only problem you’ll have with leaking is if the substrate itself is not waterproof, in which case it’s going to leak whether you replace the grout or not. Grout has absolutely nothing at all to do with waterproofing.
Elfman,
OK…so I’m now ready to grout (sanded) my tile 1/4″ lines. I’ve tried searching your site, but do you have a how to or tips on grouting?
Hey Sam,
Just take your time. I prefer to run the grout float in both directions at a 45 degree angle to the grout lines to ensure you get full lines. Make sure to squeeze almost ALL of the water out of your sponge when you wipe it and be sure to mix it correctly. The less water you use in the clean up process the better.
Hi Milt,
The seat in my shower has a chairail molding at the top and the grout line keeps cracking. i understand this is because of movement but I dont have anyother problems. can i mix silicone and powered grout to fill this and not have it crach again?
Hi Milton,
It is likely moving because there is water getting back in there and it is swelling. If the bench is improperly (or not) waterproofed then it will swell and crack. There is no product which can be placed over the top of installed tile to waterproof it and prevent it from happening again. Silicone and powdered grout mixed will not be the same color, will not cure solidly and will not waterproof anything (because it won’t cure).
Sorry for the delayed answer – you got shoved into the spam folder for some reason.
Hi,
I have a 12 inch marble tile shower with a stone type 1 piece stone type floor. typical 1/8 placement of the wall tiles
I had some water leakage and bad grout spots in the floor seam and walls of the shower due to a bad original job renovating by the contractor ~8 years ago.
I have dug out all of the bad grout and dried the shower out so I am left have a bunch of holes/spaces between the tiles and on the wall and along the seam of the floor/wall that now need to be filled with new grout.
Also the tiles are not affixed to drywall as there seems to be space behind them when I use the putty knife to remove the bad grout. There is no issue with the tiles, they are fine.
I have 2 questions please;
What type of grout should I use to fill the spaces in the wall seams between tiles?
What type of grout should I use to fill the slightly larger spaces where the floor and wall come together 1/8+ but a little irregular due to a sloppy cutting of the floor?
TIA
Hi Ad (you may want to use a different handle when posting online – the phrase ‘ad’ tends to end up in spam filters
),
If there is drywall behind your tile with no waterproof barrier then the tile is likely adhered to what is left of the drywall just fine, it’s the drywall which has disintegrated. You should use sanded grout for the grout lines and 100% silicone in the changes of plane – where the walls meet the floors.
This, however, is only a temporary fix. The grout likely began cracking or staining due to lack of waterproofing and movement in your substrate. The proper course of action is to properly rebuild the shower. The tiles will almost always be just fine, but the substrate and subsequent waterproofing on it, are what protect the surrounding structure from water damage – not the tile.
Hi Roger
We have just had our shower re-tiled and I’m really disappointed in the tile placement. Is it normal for the corner joints (from the tub edge to the ceiling) to be 1/4″ apart? And, if yes, is the usual practice to fill the corner with grout and then cover over the grout with silicone?
Hi Pat,
No. And no. The should be 1/16″ – 1/8″ apart and filled only with silicone.
Hi Roger – I’m working to regrout my shower and noticed that the previous owner may have used sanded grout (there are tiny specks within the grout lines and have rough texture) when they grouted the tiles. Not sure why considering they are 1/16″ grout lines. In any case, I’m using an oscillating tool to get the old grout out so I can apply new non sanded grout. How deep should I go with the removal? Would your previous suggestion of at least 2/3 in be sufficient? And also, do you anticipate problems using non sanded grout over potential reminence of sanded grout? Thanks for your input!
Carol
Hi Carol,
Yes, you need 2/3 the depth of the tile. Grout bonds to the side of the tile, not the substrate (or whatever is beneath it) so no problem with unsanded over it.
Roger,
I hope you can help me with two questions about ” grout issues”. We moved into our brand new home two years ago. A few months into it we noticed that water splashed on the floor of the second floor bath was leaking into the ceiling downstairs, we think that between the outside of the bathtub and the tiled floor, since the grout is cracked there. Is that normal? . How do we fix it now?
The second question is about our kitchen floor, also ceramic tile. The grout was getting dirty, so we had it professionally cleaned. Well, not only did it not clean well at all, but now parts of the grout are missing (whole segments) and others are cracked, broken or seriously thinned. So my question is: which fault is it, the cleaning company or the original installation of the grout? . And what do we do, should we regrout the whole thing?
Thank you for your help.
Hi Lourdes,
If grout is cracking (upstairs) outside your shower it is indicative of water getting into your substrate and swelling it. If it is indeed leaking downstairs it is indicative of a much larger problem than water splashing outside the tub. You can not normally splash enough water outside a tub for it to soak into the grout, into the substrate, saturate and swell it enough to exceed the saturation point so that it leaks. THAT is a lot of water. It is more indicative of water in your wall substrate around the shower leaking behind and below the tub into the framing, subfloor and joists. Your shower is not waterproofed (that’s what it looks like from here, anyway…)
Your kitchen is, in one way or another, the fault of the original installation. It could be an inadequate substrate, which would allow excess movement, weakening the grout. Or it was simply improperly mixed, installed, or cured grout. Steam cleaning, or other methods of cleaning grout, should not affect the stability of the grout at all.
Thank you for your answers, I appreciate your help.
). So.. does this help with whether out bathtub is waterproofed?
About the upstairs bathroom, I did not mean that there was water dripping from the ceiling downstairs, but that there is a water mark on the ceiling, about 3 feet long, following the outline of the edge of the bathtub upstairs. Also after looking more carefully, it is the whole perimeter of the room where the tile meets the wall or the cabinets that the grout is cracked (but not in between the tiles). And it was not caulk or silicone, but grout at the “change of plane” (I learned this from your posts
Thanks again!
Well your bathtub substrate may be fine, but I would silicone the transition between the flooring and tub really well. The grout is the reason it’s cracking there, needs to be replaced with silicone. But you already knew that.
Roger, I was re-caulking my bathtub when I noticed some mold on the nearby grout lines. I dug out the affected grout and then refilled it with some newly mixed grout (using the original grout that was applied when the bathroom was renovated a year earlier). I thought I had the right consistency. I let it set for over a week. Today, when I set out to seal the grout lines, I realized the patched areas were still wet. The grout hadn’t set and the grout was coming off on the brush I was using to seal the grout lines. I stopped and dug out the wet grout again. What do I do? The surrounding grout has been sealed. Can I just put caulk in this area as the patches are all where the wall meets the tub or should I try to grout them again? Is it possible all the chemicals I used to remove the caulk (mineral spirits, caulk remover) kept the grout from curing. I thought I wiped the area down pretty well before I attempted to re-grout.
Regards, Lina
Hi Lina,
If you mean the change of plane (corner) where the tile meets the tub then yes, dig out the grout and use caulk or silicone there (which should have been done to begin with). The reason it’s still wet is because water behind the tile runs down the wall (gravity
) and that’s where it goes, it just sits there. Be sure to leave weep holes in your caulk bead.
Thanks Roger, I should have been a little clearer. The grout lines were not on the change of plane corner but very close to it on the wall. The effected grout lines had mold where they met the caulk so I had to dig out the lines about 1 inch going up the actual wall. Would you still try to caulk or fill the lines down to the plane where the tiles meet the tub? Many thanks! Lina
No, it needs to be grouted above that change of plane. Silicone and caulk beads will eventually lose elasticity and need to be replaced (it’s normal maintenance). I would ensure that you have proper waterproofing and drainage at that change of plane, something is causing water to be trapped in there, hence the mold. Do you have weep holes in your caulk bead? That’s precisely why they need to be there.
We didn’t have weep holes when the original caulk was put in. At the moment, there is no caulk at the change of the plane–I’ve removed it all. So the change of the plane was awaiting new caulk when I tried to regrout that area going up the wall. Despite a week of waiting, I was still able to scratch off the grout with my nail. Mind you, this shower hasn’t been used in several weeks now and should really be dry. Also, where is the best place to put a weep hole in this situation. Thanks so much for your advice Roger–I really appreciate the guidance. I can send you a picture if that helps? Lina
Your grout may be past the expired date. Normally once open it’s only reliable up to about a year or so, perhaps less depending on how old it was when it was opened. The storage conditions dictate a lot of that as well. Open grout can actually absorb moisture from the air, leading to premature expiration.
Hi Roger!
OK, I just grouted yesterday and it’s cracking out already. So I’m assuming I didn’t mix it right. I was trying to use just half the bag since I didn’t have a large area to do. Must have been too watery. Anyway, I still have to dig 2/3 out, right? Or can I just dig out the parts that are popping out?
Thanks in advance…..
(love the banana)
Hey D’arcy,
Just dig out the parts that are having problems. It’s shrinking too much, that’s why it’s doing that – yes, too watery.
I’m more fond of the snowball.
Thanks so much. I already dug out the 12″ length of the broken portions, I know I can’t fill a 1″ or 2 ” portion. I will use the premix for this filler stuff. Obviously, I was unable to predict the consistency of the self-mixed stuff….
(I watched the devil banana and the yellow banana dance in sync..for like…10 minutes. Shameful.)
I just did the backsplash in my kitchen and noticed the next day (today) that I didn’t do a very good job at grouting, there are some spots i missed along with some holes. Can i go back over the area with more grout? Bare with me this is my first DIY with tiles. Thanks in advance!
Hi Jan,
As long as you do it today or tomorrow then yes, you can go over it with more grout.
Last night I removed the grout from my bathroom shower walls. Today I applied the nonsanded grout (in a gray color). I think I should have worked on smaller portions of the wall but I noticed that the grout seemed to be getting thicker so I hurried to put it on the walls. After I was finished it was a mess and I had a hard time trying tos ponge off the excess grout. I thin lines beween the tiles were thick so I used a razor to scrap off the excess grout and used the sponge again to wipe off the So here is my question, sorry, can I fill in some small gaps 24 hours later with more grout? Or do I have to remove it all and start again? Help.
DIYer, very upset
Hi Donna,
Yes, you can fill it in with fresh grout.
do you recommend grout stain?
Hi Larry,
In some situations. Some situations have better or easier cures.
My husband installed a new tile floor in July and there are some voids in the grout lines. Is it possible to fill these voids now, or is it too late? The grout has not yet been sealed and I have been told by one person that if I wet the old grout really well, the new grout will have something to adhere to. Is this true? If not, is there another easy fix? I need to get this grout sealed soon. Thanks!
Hi Missy,
It may be fine provided your floor is sturdy enough. Give it a shot – at worst you’ll just need to redo it. It would be best to dig out those areas to 2/3 the depth of the tile to allow the new grout to bond well to the tile.
Sorry it took me forever to reply. The “dig out 2/3” advice was what was originally given (I was listening to what my head wanted to hear…) I better make up my mind on this soon – the grout isn’t sealed and is getting pretty dirty. Then I’ll have another job! Thanks!
We just had tile installed with a dark colored grout and as it dries I’m noticing that there are quite a few voids in the grout lines. Is there a way to fill the voids without running into the problem of just adding a second layer of grout that is likely to crack?
Hi Keeley,
If you go over it with more grout within 20 days or so it’ll bond just fine.
We had someone put tile in our bathroom and the person shoved too much excess grout in the inside corners. How can the inside corners be cleaned out?
Hi Sherry,
If you’re careful you can use a hammer and chisel to chip it out of there. You can also use a grout saw, but it’s difficult to do with corners.
Thank you for replying Roger.
We installed a new marble floor in our bathroom about 3 years ago.When I did the grout (first time ever) I didn’t get it really deep enough in spots.It is very tight & not coming loose anywhere at all.But from hairspray & all the other sprays in a bathroom ,it is looking very dirty.Can I regrout it or do you know something to whiten it? Thanks so much
Hi Sharon,
Try getting it clean with oxygen bleach (stuff like oxy-clean). Once you do get it clean seal the marble and grout with a good sealer like Miracle Sealant’s 511 Impregnator. That will allow you to clean it easily and prevent the marble and grout from staining.
Hi Roger,
I do believe I already know the answer to my question, but i’m somewhat hopeful I may be able to avoid scraping the grout out of my recently finished kitchen backsplash. My husband and I chose to use a sanded grout on our marble hexagon backsplash tile due to the fact that the spacing is quite wide. We were lucky that the tiles didn’t get scratched, but i’m incredibly disappointed in how it turned out aesthetically because it’s so rough and looks dirty. I’m kicking myself for not having gone with non sanded-grout, and someone suggested to me that I try applying a layer of non-sanded grout over the sanded grout. I’m assuming this won’t work unless I scrape out the original grout, which I think is too much of a feat for me at this point so will probably just suck it up and learn to live with it…
Thanks
Hi Emma,
You’re correct, it won’t work. Grout bonds to the sides of the tile, not the substrate (or grout) beneath it. Get some drywall sanding sponges (fine) and try going over the grout lines lightly. You should be able to smooth them out a bit and take off any surface inconsistencies. If it gets to where you want it seal the grout so it stays that color and is easier to clean.
Roger
I was just surfing the web looking for creativeway to attack the issue of grout comming back up after a new tiling job in the shower walls. Got the answers (of course not good news) and came acroos your site.
Just wanted to says thanks for all the great information both on your site and in facebook! Your wife may want to shoot you, but, there are a lot of us that appreciate you taking the time to help answer questions.
So this is my first time and of course as I have proceeded with my project I have learned a lot. But needless to say though I have aspired to be as good as you that is not possible at this point.
So when I started putting up the tile I perhaps put a little too much thin set on the wall and it seeped in between the tiles. So now that I will soon be grouting I am trying to remove the excess using a scraper that I have. Along the way I have bought other tools but this painters scraper seems to do the job best without chipping or scaring the new tile (yup got some nicks)
1. What is your suggestion for removing the thin set?
2. Do I need to really remove it ? or how much do I need to remove?
Thank you once again for you help,
Anita
Hi Anita,
The easiest way is with a grout saw. It is a small hand tool made to remove grout, You should be able to find one in the tile section. It works well for thinset.
Yes, you do need to remove it to at least 2/3 the depth of the tile. Grout bonds to the sides of the tile, not what is beneath it.
I really wish other sites, ehow, DYI….. were as good as yours! When I started this project I did my homework and no where did I ever see that you were suppose to put thin set between the backerboard and the sub floor! If I would have seen it I would have done it, matter of fact I remember seeing on one site that they said not to have anything between the two including paint or primer! So here I am with a floor that is done and Beautiful by the way but not done right! Guess I will have to decide what to do from here but I really don’t want to go down to the sub floor again so I will make sure it’s not the way I mixed the grout and I will remove all the grout and thinset in the grout lines. Re-grout then hope and pray that it stays in and I don’t have to pull the floor back up! Time will tell and you are probably right I am just not ready to throw in the towel and pull it all back up! Thanks Roger, your not a buzzkill, well maybe a little!! LOL!
I wish I would have found this website before I did my floor!!! LOL! I found it when I decided to pull cultured marble tub surround off of the wall and put up tile, that’s when I needed (or so I thought) I needed to know about waterproofing! Should have done it on my floor surface too, Dummy me!!
Oh well now I have the problem of my grout on my floor cracking and peeling up, could be that it’s because I didn’t thin set the cement board to the subfloor(again dummy me 
) or it could be that I mixed the grout up wrong (started coming up only a week or two after putting it in). I will not be taking the tiles back up and re-doing every thing (at this point at least) as it’s my main bathroom and we tend to use the masterbath the most, the mainbath is for visitors. I do know better now when I go to do the masterbath though, thank you Mr Elf!! 
My question though is could my problem be from (1) having too small of grout lines (I used small brads for my spacers about 1/8 inch) and or (2) having thin set smushed up those lines up too far and I didn’t remove it well enough???? I also did not like the fact the grout was not deep enough and I put another layer of grout on top of the dryed grout, approx 12 tp 24 hours after the first layer. I guess either way I look at this I need to dig all the grout out of the areas effected and re-grout. I am really hoping it’s not a floor issue and it’s just a grout issue, I do not want to pull up my new granite floor!!! I guess only time will tell and it’s a good thing I got lots of grout and a great ELF helping me!!
BTW could my walking on the new floor and by walking on it I mean I re-did my tub surround including demo after I put the floor in as I wasn’t going to do the tub surround until I decided I hated it so much! So I did major remodeling of the tub surround (demo, water proofing, tiling….) and the grout coming out of the lines are the tiles that were the most walked on and next to the tub!
Love your site and it saved me lots of hair (didn’t pull mine out) when I finally found it and how to water proof correctly!! I used the paint on membrane and it worked great!!! And my tub surround is Beautiful as well as water tight (too bad I chipped my tub
during demo or it would have been a perfect job)!!!
Hi Janet,
Your grout problem is not due to small grout lines. It may be due to the second layer of grout, but doubtful. It could be due to not digging thinset out far enough, but that would only happen in the particular tiles where it was exceedingly high. I know you don’t want to hear it, but it is likely due to lack of thinset beneath the backerboard. The fact that it is happening where you walk on it most is indicative of excess movement in the substrate over the traffic areas. If it’s coming out where you walk on it, walking on it is causing movement. Most movement is due to either improper coverage between the tile and substrate or lack of thinset supporting your backerboard.
Sorry to be a buzzkill.