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.
Sorry, no snarky remark just a question about wide grout lines. Roger, I have polished concrete floors on my entire main floor. There are 1″ decorative grout lines in various places that run the length of the room. The grout has gotten very dirty and is to the point of being very difficult to clean. At this point I think removing the old grout and installing new is the way to go. Do you have any recommendations for the easiest way to REMOVE the old grout? Do I have to make sure every last bit of the grout is removed to get good adhesion to the concrete?
Thanks,
Rob
Hey Rob,
Get one (or two or three) of these: Grout removal tool You don’t need to remove ALL the grout, but you should have most of it out for a proper bond.
What do you think about groutrenew colorant? So far I am loving it. It covered all the stained grout. I am looking for short term fixes because I don’t own the home, yet if I want it presentable its on me. There is a small joint between the counter and back splash where the grout is missing. Can I just fill that since it’s missing? I don’t have any tools like you mentioned and as a girl I’m not sure I would even know how to use them.
Hi Courtney,
No idea, never used it. You can fill that with grout but you’ll need to eventually replace the grout with silicone. It’s missing because it’s a change of plane and should be siliconed. It will likely crack out again so it is only a short term fix.
I have recently had tile work in a shower floor, 2 inch square tiles and unsanded polyblend grout was used. most grout lines were 1/8 or smaller butthe lines on the east and west sides of floor were a bit larger maybe 1/4 the contractor used unsanded grout in these lines as well. I waited two days as reccomended before sealing the grout and noticed small hairline cracks in the wider lines. I did not seal the grout and called my contractor he told me he would stop by and add more grout to those lines as they are a bit shallower than the others, this is a very recent install 4 days ago. should I ask him to remove this grout and use the same color sanded grout? Remove some of the new grout and add more unsanded to the larger lines. I am just concerned that the newer layer of grout wont bond to the first layer.
Any advice will be appreciated
Thanks
Eric in Denver
Excuse me i meant the larger grout lines are a bit deeper so additional grout could be added. not shallower.. sorry
Hey Eric,
It’s due to the unsanded shrinking. Normally you can add more to those to fill the cracked areas. I would let him try that and give it a week or so to make sure it’s filled before sealing it. If it cracks again I would have him remove it and use sanded in the larger ones.
I cannot get the grout to stick in between my porcelain bathtub and the first tile line. What am I doing wrong??
Hi Bobbi,
You are trying to put grout between the tub and tile. You need to put silicone between the tub and tile. If you do get it to ‘stick’, it will soon crack and begin to fall out anyway.
Roger. I have 1/8″ grout line in our fully tiled shower. one corner where the tile wallmeets the tile floor there is a hair line crack that stretches a couple inches in all three directions from the corner. Up from corner and shooting out along the shower/floor line. _l_ The work was done 4 years ago and mildew/mold always collects where the crack/s are. I spray bleach every month so it looks better, but I’m tired of the constant cleaning. The crack hasn’t increased since it first showed up a couple months after being completed. Is there anything I can do short of removing the old grout there? Can I just clean it well and maybe just run the grout saw over it a little to create a suraface to stick to and just run some some grout over the crack then seal in hopes that the mildew will not return? Thanks so much!
Hi Lisa,
The problem is you have grout in your corners. All changes of plane need to be caulked or siliconed. You need to remove the grout and silicone it instead.
We had a tile shower installed recently, and used 6″ tile for shower floor. Some of the grout came up within days of completion, so the workers removed all of the grout on entire floor, then regrouted. After waiting 72 hours before using the shower, all is well except for one 3-4″ section between 2 tiles, where the grout came up again. I am tired of workers in my house lol, can I use a colored caulk for this small area? Or is it in my best interest to call the workers to work on it again?
Hi Deby,
I would call them back. If you do that and the underlying problem still exists (it may be movement or incomplete bond rather than the grout) then they are no longer responsible for it. Caulk will end up being a pain anyway, it’ll lose elasticity over time and become brittle and debonded from the tile.
The grout in our shower has a lot of mold. My wife wants me to re-grout. My thoughts are using a grout saw, remove most all the grout in the whole shower, and replace with synthetic-mold resistant grout. Is this the best way to resolve the grout replacement, or is there an easier way? Or do I spend my time just trying to get rid of the mold with chemicals and scrubbing? (I know the main reason for the mold is the lack of a ceiling fan. I will install one prior to completion.)
Hi Rodell,
With a caveat: if your shower is properly waterproofed and drains correctly BEHIND the tile. i.e. the mold is not caused by improper drainage behind the tile.
Yes, you need to remove at least 2/3 of the depth of the current grout before regrouting. Not sure what you mean by ‘synthetic mold-resistant’ grout – epoxy? Urethane? If so, either is a good choice.
Another question.. Is it possible to use colored silicone sealer to replace grout in the shower. At the shower entrée point is a raised area, about 6″ high. Most of the grout is breaking up and I’m sure the wood underneath is wet… I plan to remove all the grout and tile to dry it out. But when putting it back together I would like to use silicone sealer. And is it okay to remove a small amount of grout in other areas of the shower and replace with silicone?
I believe what you’re talking about is the curb. If that’s the case it is indicative of the curb not being waterproofed. No amount of anything over the top of the tile will fix that or prevent it from getting worse and causing more damage. The curb needs to be rebuilt and waterproofed.
And no, you should not use silicone in place of grout. They are two completely different products for different applications. The silicone loses elasticity over time, once it does this it will pull away from the tile and it will look worse. Ever see a bead of silicone around a tub that has mold and all sorts of nasty stuff behind it? Picture that in all your grout lines.
I am attempting to fix old grout/ caulking in the seam between the tile and the older tub. I have re caulked this area a number of times in the 13 years that we have lived in this house. Pulling out the old caulking , cleaning very well, allowing to dry overnight before reapplying new caulking. 13 years ago we had this bathroom remodeled, leaving the original tub ( because it was in good shape) and the worker tiled over the old bath/shower tile. Lately the mildew that was under the old caulk was showing through. Driving me crazy , because I am a clean freak. I removed all the old caulk and some of the original grout and cleaned everything very well with mildew remover , etc. After scrubbing the tube and tile, I let it dry out over night. Today I had a premixed , in a tube, grout. I applied it ,, just like I had applied caulking in the past. ( thinking this may last longer or work better than the caulk I had used in the past , probably bad idea ) After about 2 hours I noticed a small crack down the center of the seam. I applied a tiny bead of grout again over the crack. I am now noticing ( about 6 hours later) more tiny cracks down the center. Needless to say I am frustrated. Can I just run a thin bead of caulking over the grout and if so , how long do I have to wait before I add the new caulking? Needless to say I have a bunch of kids and having a shower out of commission is hard. BUT I have gone this far I am wanting to do this correctly. At least all the mildew is gone from where i scrapped it out. I really hate the idea of having to scrap out all this grout to re-caulk? YIKES. thanks so much for your input! suzanne
Hi Suzanne,
I don’t know what the premixed grout product you’re talking about may be, but it certainly isn’t what you want in that change of plane. Your best bet would be to use 100% silicone there. If you fill the tub before you silicone it that will widen the space to it’s largest gap, install your silicone and let it cure, then empty the tub. This will compress the silicone a bit as you empty the tub and prevent it from pulling the sealant away from the tile every time you fill it or set into it.
Question. We have installed two bathrooms approx. 1 year ago and both had polished full pebble stones as shower floor, Wedi Shower pan and also StarQuartz grout. Seems that both jobs are having issues with the pebbles not adhearing to the mortar causing deflection and grout coming out – mainly around the drain. Can you provide any insight of the problem and a fix?
Hi Susan,
It could be any number of things, all of which I would need more information before venturing a guess as to the cause. How was the wedi pan installed onto your substrate, what thinset and what size trowel was used to install the stones? Can you tell if it is the stones moving on the pan or the entire area of the pan moving? Can you actually see movement or insinuating it because of this issue?
I used broken glass tile pieces to make a mosaic on the top of my raised dog feeder (I used the factory edges of the glass tiles around the edges of the feeder so they would be smooth). Saturday I used thinset mortar to set them in place and then yesterday I used sanded grout to fill in the grout lines. This was my first experience doing this. Today it is apparent that I sponged away too much of the grout because the sharp edges of the broken glass tiles on top can still be felt. The glass pieces are all level but I didn’t leave enough grout! Is it too late to just add more grout? If not, what can I do? I love how it turned out…minus the sharp edges. Thank you so much! -Summer
Hey Summer,
Since you just grouted it you can likely soak the grout down really well (the installed grout) and regrout.
Hello,
I just discovered my shower in the basement bathroom had been leaking for some time as my laminate floor started to show black spots coming through the laminate flooring. After pulling the laminate flooring the whole 500sq ft vapor barrier has water under it. Should I throw all the boards away as not all of them have water damage, i am worried about mold from the floor? S…cks but have to move on!
I have the installer for the tiled bathroom shower coming tomorrow to look at the damage. I removed the interior tile of the curb of the shower pan and discovered he cut the waterproof liner level with the interior tiled shower floor, it should have been draped over the curb correct?
My question is what shower system would you use as this shower pan will have to be removed correct? I can send a picture but he webpage box won’t accept.
Thanks
Hey Dennis,
Yes, the liner should have been wrapped over the curb. Yes, it will need to be removed. I would likely do it with kerdi-board on the walls, mud deck and kerdi on the floor. As long as the water was UNDER the barrier you can probably save what isn’t wet.
Last Monday (today is Thursday) our new Armstrong floor tiles were grouted. The floor tiles are only about 3/16 inch thick. No one walked on the grout until Wednesday. The installer left valleys in the grout lines and now we are seeing numerous hairline cracks. Will filling the valleys with more grout be satisfactory or does all the grout have to come out and regrout the full 3/16 inch? Please let us know as soon as possible before I pay the installer. Thanks
Hi Bill,
Sorry for the delay, been out of town at the new Schluter facility all week.
How large are the valleys? With 3/16″ grout line it will dip a bit, but not overly-so. The hairline cracks are unacceptable, but you may just be able to go over that without problems. If the valleys are excessive you’ll need to remove that grout. If they are excessive it also likely means that the grout had too much water in it causing it to shrink as it cured (more than normal) which caused the valleys and the hairline cracks.
Hello kind sir !
I recently had some tile installed and noticed that the installer left complete gaps in some areas where there is no grout at all. In other areas, there are small air holes. Can I simply fill in the gaps with new grout or would this still be considered top grouting and I should still cut down the original grout ? Same for the air bubbles ?
Thankyou !
Hi Matt,
Sorry for the delay, been out of town at the new Schluter facility all week.
With the gaps you’ll want to remove some of the grout around it then regrout. You should be fine with just regrouting the air pockets.
Hello. I have a hairline crack in my new shower wall tile (new as of February 2013!). We noticed the crack about 6 weeks ago and have not used the shower yet – the tile guy was supposed to come back and fixed it and of course he has abandoned us! In any event, the tile guy is known for very little – tiny, hardly can be seen grout lines! So, in this case, the crack IS the grout line!!!! It is so tiny you could not even get a saw in there to clean it out and redo! What should I do??? I would be glad to send you pics of the project! The tiles are large 17″ x 23″ in size…not sure if that matters, but thought I would mention it.
Hi Carolyn,
I don’t understand what you mean by ‘the crack IS the grout line’??? Is the tile cracked or is the grout cracked, you haven’t clarified that. I’m assuming the grout, in which case you should be able to mix up some more unsanded grout and regrouting it. If that’s not the case you’ll need to give me some more info.
Hi Roger – Sorry for the confusion – The grout is cracked – it’s just that the grout line is so narrow that the hairline crack is the same width as the grout line. I hope that helps… I don’t think it is wide enough for me to cut the old grout out and replace it with new.
If it’s that small you can just go back over it with unsanded grout. It’s likely that it either wasn’t properly filled to begin with or the grout shrunk and pulled away from the tile as it cured.
Roger, Thanks so much! I will do that as soon as possible! Showering in the guest bath is getting old!
We just had an entire bathroom rip-out. New tiles on walls and floors. The contractor used wonderboard on both, not sure about anything else…BUT, in the floor tiles, most of the grout is cracking and lifting. He used polyblend unsanded grout and yes the spaces are 1/16. We noticed this right away (within 12 hours) and he regrouted the floor. Now 20 hours later, as I lightly swiffered the floor, the same thing is happening. Please tell me why and should I have him re-grout again.
Oh and I also noticed in the shower that tiles are inconsistent in the depth of which they were placed and I have ridges with highs and lows in the tiles.
That is simply shoddy workmanship.
With only 20 hours it could be the grout shrinking (if it’s just coming away from the sides of the tile) or it could be movement in the substrate if he didn’t install thinset under the backer.
Hi Roger, I a m trying to help out a friend that had a tile floor put in years ago. The installer did not put down a sub-floor (yes, we know). Well, the solution to fix the problem is not an option. This is an older couple and doesn’t want to go through that. The owner doesn’t mind doing a little experiment, anything to possibly fix the problem. The caulk line going through the center keeps having the grout fall out. It’s not really that noticeably, but, bothers the home owner. Here are the facts: dark, multi-color tiles, 12 x 12, sand grout (gray), problem location: grout line from one corner diagonally to the other corner. My question is: I know you shouldn’t use caulk in the center in replace of grout, but, as you said, grout on top of grout isn’t going to work. I thought if we got a color close it would fill the gap and make her happy. Will it crack again?
Hi Nikki,
Yes, it will crack again. There is obviously movement there causing the cracking, giving it more stuff to crack isn’t gonna solve it.
What you can do is find a silicone that matches fairly closely, remove the grout from that grout line and replace it with silicone. The silicone allows movement to an extent and will not ‘crack’ or become separated from the tile (unless there is extreme movement), grout allows no movement at all. It is, essentially, a soft joint and completely acceptable.
Hi Roger,
We installed tile in our kitchen, and the next day two of the tiles has popped loose and the grout completely cracked. It turns out a part of our sub floor came loose and was bouncy. Anyways, we fixed the problem, cleaned up all the thin set mortar, and relaid the tiles. So my question is, when I reapply the grout, will it stick to the old grout (3 days old) or do I need to remove all of it and start over? God I hope not. I also noticed that in a few places the grout doesn’t look like I want it too. I am a bit of a perfectionist, and even though my hubby says it looks fine, i hate it. Can I scrape some of the grout out down to the sub floor and then re apply it? Thanks for this site.
Hi Michelle,
Yes, it will bond just fine if the old stuff is only three days old. (you’re welcome
)
Yes, you can scrape out the spots you don’t like and regrout them.
Just recently had tile installed in my home – they are tile planks that look like wood, we are very happy with them except in one small spot in the grout there is what appears to be a hole, like a little chunk of grout went missing. The grout is unsanded, which we opted for because the tile was supposed to be laid with 1/16th grout lines (it wasn’t). We still have a bag of the grout that wasn’t used by the installers – can we mix it up and just fill in the hole? Or is there something else that we would need to do. Thank You.
Hi Tara,
Yes, you can fill that with more grout. Sometimes a portion of the grout will bridge a hollow area, then the bridge collapses and leaves a missing portion. Nothing major.
I got a new house I wanted to put new tile floor in i did and the grout is to shallow and cracking we use a sand grout it only less then a mouth old is there a easy way to fix this? The person who put it in said they can just grout over because it shallow but what I have read that not right! So can u pls tell me a way to fix this?
Hi Brittany,
There may be an easy fix, there may not be. No way to tell without knowing WHY it’s cracking. How was the floor built? From the subfloor up?
I have a question we just made a new 3 sided shower with tile and such on the ceiling…..some areas on the wall have small hairline cracks 2 dyas after we grouted…. how can we fix these. I mean its brand new grout and not sealed yet. I just want it all done right before sealing. it’s a non sanded grout because there is some glass tiles. I don’t understand why some spots did this? the walls are solid the shower base is solid, we used good grout ployblend.
Hey Shawn,
Your grout simply shrunk. There was too much water mixed into it or too much was used when washing it. Also if your grout lines are almost 1/8″ that could be a factor as well. You can go back over it with more grout and it should be fine.
On a side note: Polyblend is, in my opinion, the worst grout on the planet – it shrinks all the time.
Roger,
We have a 40 year old terra cotta tile floor that was set into the foundation of the addition to our 1862 farmhouse. The floor of course settled and the tiles cracked and are uneven. The grout doesn’t come up to top of tiles so it is a bit rough and also uneven. It is dark gray in traffic areas (due to dirt, etc.) and light grey in non traffic areas. I am wondering if they didn’t even grout but just pushed the tiles into the concrete? Could we re-grout over that to make the grout more even with the tiles?
Thanks so much for taking the time to answer us…also, any good solutions for removing self-stick vinyl tile adhesive from the terra cotta tiles?
~Carla
Hi Carla,
Old-school tile setters, especially with terra cotta, would simply use the setting mortar as the grout also. That’s likely what you have. If you want to regrout it you’ll need to scrape out 2/3 the depth of the tile first. Grout bonds to the sides of the tile, not what’s underneath it. You need to give it something to bond to.
Get some denatured alcohol and a spray bottle and spray the adhesive, let it soak, then spray it again and scrub with a white scrub pad, vacuum it up. If there’s any left just repeat. That’s normally how I get old adhesive off.
Thanks for your quick response Roger. We decided to paint the floor instead. What tips do we need to keep in mind when doing that?
Paint the floor??? I don’t have any idea, I don’t paint floors.
If you’re painting over the tile I know there are special kits you can use to do so, but I don’t know anything about them, never used them.
Hey, I just bought a home with a newly renovated bathroom. The tile/grout are separating at the corner (90 degree wall-to-wall). Can I just fill the gap with caulk?
Hi Craig,
You can, but it won’t last – so no.
You need to scrape the grout out of there first – then it’ll last.
Hi we have recently had our kitchen floor tiled but have noticed that on some of the tiles the grout is cracking, we don’t want to do the whole floor again, any ways of getting around it?
Hi Nasima,
Well, you can regrout. But if your grout is cracking it is due to movement of some sort. Which means your floor was not properly prepared for the tile, some facet of it was installed incorrectly or there is not proper movement accommodation for the tile. That means that it will eventually crack again, and will continue to do so until the underlying problem is remedied.
Love your site! And your reason for starting it. Had to like you on FB. I guess your jackassedness got me subliminally for me to have chosen that word. :o)
Take Care,
Helga
Sigh, Pebble Floor in shower. My first time doing this…and I removed too much grout between some of the pebbles, creating little buckets which will hold water. I know I can’t grout over grout. But, is it feasible to use a silicone grout over the sanded grout?
Much appreciated!
Hi Helga,
No such thing as silicone grout. Not sure what you plan on using?
Hi There, thank you for taking the time. :o)
This particular one I have here is made by MAPEI and has a label saying “Keracaulk Sanded” then Siliconized Acrylic Caulk. OH! So, there you go, it’s not grout, it’s caulk, made to match the colors of the grout they sell……and I had to do this over the net. I’m usually satisfied just making a jack ass out of myself at Lowes..
I make a jackass of myself EVERYWHERE! Hell, it’s even at the top of my website.
No worries.
Hi. Last night I just finished replacing my bathroom linoleum floor with ceramic penny tiles. I have two problems. The most distressing to me is that a roughly six inch section of grout did not dry to match the color of the rest of the floor. For whatever reason the grout did not lighten as it dried. It is of course right in the center of the room. Please tell me that there is some way to lighten this without digging it out. My second concern is that in a few places there are what look like pinholes in the grout. I assume there were air bubbles that worked their way up during drying. Do these pinholes need to be filled in with grout or will sealant seal these up? In case it matters I used unsanded Mapei Keracolor grout in pale gray. Thanks for your help.
Hi Michelle,
Unsanded grout will have pinholes if you aren’t extremely careful with it. It’s a pain in the ass. Sealer will fill it, but you’ll still see it. The discoloration may lighten up over time. Unsanded is more dense than sanded and may retain moisture longer. It could take a couple of weeks. Do not seal it until it lightens. If it does not lighten you either have vapor dissipation under that area (doubtful if in the center of the floor) or it may actually be the rest of the grout that is lighter than it should be?