Your grout is cracking for one reason and one reason only: your tile is moving. That’s it. Okay, that’s not it – Unless your grout is non-sanded and was installed in the last 28 days – your tile is moving. That’s it. Yes, 28 days has significance, it is the amount of time it took my teenage son to clean his room. It is also the amount of time it takes for grout to fully cure.
So let’s figure out why your grout is cracking:
Your grout is newly installed – incorrectly
If you do have grout that was installed within the last 28 days then your grout is not actually cracking – it is shrinking. Either your grout lines are too large for non-sanded grout (smaller than 1/8″) or it was incorrectly mixed. NO! You cannot simply mix up more and fill it in. Read this post about adding more grout to your grout lines.
If your grout is not fresh, well, you need to repair the reason your tile is moving. And stop using your pogo stick in the house. Diagnosing the reason your tile is moving is extremely varied. It could be anything from inadequate deflection in your flooring for the type of tile all the way up to and including the aforementioned pogo stick.
The most likely reasons your tile is moving:
Your tile does not have proper thinset coverage
The most common reason I run into is improper coverage. This simply means that there is not enough thinset beneath your tile to properly adhere it to your substrate and support it. If there are any unsupported areas beneath your tile along the edge or in the corner of the tile, walking on it will eventually work what little support it may have loose and the tile will move down and up every time you step on it. The tile moves, the grout does not. The grout loses the battle and starts to crack out. By ‘crack out’ I don’t mean like that ridiculous Intervention show on cable, I mean it will start to crack and come loose.
To fix this you need to remove and properly reinstall the tile. If it is only one tile it may be an isolated incident in your installation and you will be fine. If you have cracked grout all over your tile installation it was either improperly installed or . . .
Your subfloor is moving
If you have a wooden subfloor and your tile is directly installed to it – go pick out new tile. That is more than likely an improper installation. While tile can be installed directly to plywood it requires a VERY specific method. And I do mean very specific. More than likely it is simply installed improperly probably by someone that did not know any better. If it was properly installed over plywood, well, your grout wouldn’t be cracking. Start reading this paragraph all over. Or . . .
Your backerboard was improperly installed
If you have Hardiebacker, Durock, or any other type of cementious backerboard beneath your tile it should have been installed in the proper manner. It needs to have thinset beneath it, it needs to be screwed down (properly), it needs proper spacing, etc., etc. Read How to Install Backerboards for Floor Tile to see all the things that should have been done.
More than likely there is no thinset beneath your backerboard. Thinset is not used to adhere the backerboards in any way – it is used simply to fill voids beneath the backerboard. It is placed there specifically to prevent your tile from moving. Moving tile leads to cracking grout. But you knew that – or you should start reading this page all over. This would be another time to start shopping for new tile.
Other reasons your tile is moving
You do not have expansion space around the perimeter of your tiled room. No, the tile will not expand – but your walls do. If there is no space between your tile and walls it will force all the pressure into your tile. This will cause cracking grout and, eventually, ‘tenting’ of your tile.
You do not have expansion joints in your tile. For every application there are specific spans of tile which can be installed before a ‘soft joint’ is required. This is simply a grout joint filled with a matching caulk or silicone to allow for movement without cracking your grout or tenting your tile. Most of these measurements are over 25 feet. So in English: if your room is not 25 feet long or wide this is not the reason your grout is cracking.
If your tile is on concrete – directly on concrete – your slab may not have proper expansion joints or the tile installation did not honor those. If installing tile directly to concrete (and you should not) there needs to be a soft joint directly above, or two inches on either side, of the slabs expansion joints. If not your slab will move differently than your tile.
And there could be a host of other, less apparent or less common problems. However, if your grout is cracking it is probably for one of the reasons above. The method of repairing it depends entirely on why it is cracking. Most of it, as with most tile installation problems, is due to improper installation.
Or your pogo stick.
If you have any questions about the proper way to repair your tile or grout just leave a comment. I answer every one of them – really, look around the site. I’m just super cool like that.
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Hello,
I just had my bathroom gutted and totally tiled floor to ceiling. All is fine on the walls except where the wall tiles meet the floor tiles. There is a fine line of cracking in the grout…in places also some areas where it just popped out. Also it is all cracked out where the floor tile meets the wood threshold. It was done less than a month ago.
A few questions if you don’t mind:
Is it possible that the tiler used wall grout between the floor and wall instead of the heavier floor grout? …should floor grout have been used?
Can I dig it out and redo it with the floor grout? Should I then caulk it?
Also the bathroom floor is not heated and the house is very cool.
Thanks,
Susan
Hi Susan,
No such things as floor grout and wall grout – there is only sanded and unsanded. Read through my article. Any change of plane, or where tile meets a different material (like the wooden threshold) needs to be filled with either caulk or silicone. Different planes will move in different directions, flexible caulk or silicone can handle that movement – grout can’t.
Hi. Had a marble hex installed in our very small master bath. The contractor assured us that the subfloor was reinforced, then mud, then thinsulate. Problem is that althought the tiles look great, when you walk on the floor it is uneven and there are small depressions that feel almost spongy. Contractor looked at it and said it was properly reinforced. When I pointed out that the prior floor was solid and eve, he had no real answer other than to say that he’d have the tiler come over to take a look. What is the likely problem? I don’t trust the tile guy and want to have some understanding of what went wrong. The fact that I can feel the intermittent “holes” and spongy parts doesn’t sit real well with me. Thanks
Hi Kim,
Whatever he thought he was using thinsulate for, I have never heard of, nor can I find any reference to, using it under tile. At the very least it is a very, very obscure installation procedure, one not approved through the TCA standards, and one I have never heard of. That is a LOT of red flags for me. Given that thinsulate is (in construction) utilized as sound suppression it is, by nature, a thicker ‘spongy’ material. That, I believe, is where the problem is.
I may be wrong, there are different methods in different parts of the country, but I seriously have at least heard of most of them, and I can always find at least one reference on the entire internet – this one has none of those aspects. I would ask him for some sort of documentation about his installation procedure regarding the thinsulate, and ‘I’ve been doing it this way for 25 years’ doesn’t count.
hi Roger–my mistake–thinset, not thinsulate. Sorry. Here’s the thing…you can feel the up and down of the floor joists through the tile in addition to some soft spongy spots. The contractor says the floor is not moving. We found 2 cracked tiles (we don’t even have fixtures/toilet etc. in yet), but no cracked grout….yet.
Oh, thinset.
That drove me absolutely bat-shit last night. That’s how my brain works, if I’ve never heard of it I wanna know about it. No biggie. 
It sounds to me like something is moving. It may be either improper support for a mud deck installation or areas of improper reinforcement or hollow areas of the mud deck. If it’s spongy it’s wrong – period. Something is wrong and with a mud deck it’s nearly impossible to tell what it is without an actual physical inspection.
what happens to a bridge without an expansion joint on a hot sunny day
It will bend, twist or collapse. That’s why they place expansion joints in bridges. Haven’t tiled a bridge in a while, though.
Hi Roger My house has floor trusses 24″ on center. Out in the living room and dining room where the truss span 26′ there is a lot of floor flex. But in the kitchen there is a supporting wall in the basement so in the kitchen the trusses only span 9′. A freind who was a flooring installer for 20yrs and now is a estimater has tried to talk me in to not using ceramic. He says in order to get away from the flexing I would have t0 put another 3/4″ of sub flooring over the 3/4″toung and groved that there now. that would put the tiles way higher than the 3/4″ hardwood they have to border up against. Could I use the interlocking plastic tile holders that are on the market. They have a specific pre mix grout that stays flexable for up to a 1/4″of movement. Snap Stone is one option another is just the trays that any 12″ tile can be glued in. I did a water in the glass test that Craig told me to try and the water does move alot. Are these floating tile floor systems being used alot and are they any good.
Hey Terry,
Craig is correct. I don’t know much about the products you’ve mentioned. I have done several floating ‘wood’ floors, but the stuff with tile is not something I use.
My ex-contractor tiled my small bathroom floor directly over plywood. We haven’t even moved into the house yet, and already one tile has cracked and most of the tiles have broken grout and crunch when you walk on them. Under the broken tile was a joint where two pieces of plywood meet. One plywood piece flexes a tiny bit. Most of the tile were so loose, I could pick up the tile once I removed enough of the grout. What should I do? I am even more concerned about the walls he tiled around the tub. I am sure he used greenboard behind the tile. God only knows what kind of thinset or worse he used to attach tile. Probably used adhesive. What can I do. I will have to do it myself. No money for more contractors!
Hi Tina,
Unfortunately the only correct solution is to remove the floor tile, install a proper substrate, and reinstall the tile. You may be able to save the tile, I don’t know. It normally isn’t a good idea but I also understand budget issues. If you can get it off of there without too much trouble you can reinstall it.
As far as the shower it will need to be removed and replaced with proper waterproofing. I can answer any questions you have during the process, just feel free to post questions and I normally answer them nearly every day after work.
Hi Jan,
You can grout the areas with latex modified grout (which most powdered grouts already are anyway) and the color will likely be different. The problem doesn’t sound like a grout problem – I can nearly guarantee it. The problem sounds like lack of thinset beneath your backerboard. If it has cracked since week two then it is due to movement in the substrate. I install tile over crawl spaces all the time. Provided the substrate is properly prepared, it’s never a problem. It seems like your substrate was simply not built properly.
We just laid our tile this weekend. 12×24″ porcelain with 1/16″ grout lines. We haven’t grouted yet and while I was cleaning the grout lines, I noticed one tile corner appears to not have enough thin-set under it. It was our first experience working with the stuff and didn’t have the right consistency until we got to the second batch. Should we try to fill the void with thin-set somehow, or work some grout down in there? And if so, do you have any suggestions for how to get it into such a tight gap?
Hi Loren,
You can mix up some thinset and pack it into the grout line with your grout float. Pack it in there really well in order to get it beneath the corner. Don’t worry about making a mess. Once you get it packed in there you can clean out the grout lines in order to grout. That should get your thinset beneath that corner.
My grout is coming up here and there after 2 years and the tile is not moving. I think it is because I didn’t mix the sanded grout correctly. There are 4 or 5 cracked tiles too. I think because I didn’t put enough mortar down in a few places or I didn’t trowel it correctly so it wasn’t even. Or I dropped something on the tiles and they just cracked. At any rate, I think it is installer error – by me.
Hey ks,
Provided you have a properly built substrate that is a possibility. However, if you are just now having problems with your grout after two years it has nothing to do with mixing of the grout. It is likely movement in the tile or substrate. If you do not have proper coverage the tile will move, even the tiniest bit, when walked upon which will eventually crack grout and tiles.
Unfortunately the remodel contractor did not put backerboard down on the floor and the grout is cracking and coming up. We have paid 2 people to re-groud using sanded and unsanded grout. Still it comes up. I don’t think that we can put backerboard down as I think that the bathroom would not be level with the hall floor. I know that the contractor put something down (pink) to make it water tight. We used 18″ tiles. I do not know how to get this fixed and it looks so bad, right in the middle of the floor. If I had someone take the 18″ tiles up and re-secure the plywood and then go back with smaller tiles would that work. We have already had someone go under the house and check to see if the bathroom floor is level, it was, but we put a jack under the house for a more secure floor. HELP!!!
Hi Steve,
The problem has nothing to do with the size of the tile, whether the floor is level or not, and especially not the grout. The grout cracking is a symptom of a floor with improper deflection ratio for tile installation. This simply means that it ‘bounces’ too much, or is not strong enough to prevent movement in the substrate, when it is walked upon. The pink stuff he put down is likely redgard – that won’t fix it either.
For a proper substrate you must have a deflection of L/360. You can check your deflection ratio here: John Bridge Deflecto. Once that is up to what it needs to be you need TWO layers of plywood totaling a minimum of 1 1/4″, then a substrate such as backerboard or ditra, even redgard, to adhere the tile to. There are some products such as DitraXL which will allow you to go over a single layer of plywood, but those are the basics.
Your grout is cracking because your floor is moving. Smaller tiles won’t help, there is even more grout to crack, and regrouting, as you’ve seen, won’t help either. You are only fixing the symptom – not the disease. Note that it is doubtful, as it always is, that you will come out level with your hall floor unless you use specific products installed in a specific manner (this depends on what you are working with), but there are transition strips available to ease the difference. The most important aspect is a proper substrate – you need that or no tile installation is going to last long-term.
I need to replace my shower floor tile. And when I went to remove the tile I was wondering can I top off the uneven mortar with mortar before putting down thinset for the new tile? Would it adhere if I put a slurry of thinset on it before I put the mortar on it to fine tune the rough slope?
Hey Allen,
Yup, no problem with that provided your waterproofing is intact and works correctly. And yes, use a slurry under your patches.
Roger, what is the minimum thickness for the mortar to fill a patch? The reason why I’m asking
. Also do you have a video or e-book on how to trowel the mortar. Thanks for your help.
because the whole top of the mortar bed looks pretty uneven like it can use a fine coat on top to even it out.
Would you take the whole top surface 1″ down and work up from there , how would you handle it
Hey Allen,
Normally you can have a patch about 1/4″ if you use thinset to adhere it to the current deck. If you just mean a thin layer coat to even things out you can do that with just thinset as long as it doesn’t need to be over 1/4″. No videos or ebooks yet – it’s on the list.
Hi Roger – Great web site!!!
I have a 4’ X 5’ small bathroom that will have wood floor molding around it. The 1st question I have is: should the molding be installed first and then lay the 12” X 12” stone tiles down leaving a 1/8” space between the tile & molding to be filled with grout later on? Or should I install the tile close to the walls and place the molding on top of the tile?
Secondly, the SANDED grout the tile company sold me has instructions that state that the grout should be used only on tiles with grout spaces GREATER than 1/8”. Should I use the sanded grout or return it and purchase un-sanded grout?
Thanks!
Richard
Hey Richard,
The tile should be installed first then the molding on top of it. The sanded grout can be used with 1/8″ grout lines – I do it all the time and actually prefer sanded for anything at or larger than 1/16″. No problems at all with that.
I am tiling a bathroom that is approximately 25 square feet minus the shower. I made a mistake that I hope is not too bad. I walked on the floor about three hours after it was down. I think i only stepped on the same tile or two. I was too consumed with some spots that I saw that I wanted to wipe up (mixed in with my limited experience). How will I know if I damaged the thinset?
Hey Chris,
After the installation cures go in and knock on the tiles. Knock on the ones you think you walked on as well as the ones around them. They should all sound solid and they should all sound the same. If one or two do not sound like all the others, or sound hollow, it should be removed and reset.
Hi
I need to either replace my showers caulking or replace it with grout. I have a pebble floor in the shower that butts up to tile on the walls. The guy that installed it didn’t do a very good job at filling in the crack between the floor and the walls so we had to caulk it. Right now I have cleaned the old caulking out and I was going to replace it but want to know if I should grout it instead? Some areas are pretty big and spacey so I don’t know if grouting is my best bet. Could you give me some insight please.
Thank you, Sue
Hi Sue,
Although there technically should be caulk at all changes of plane with pebbles I normally grout that area. If you can do that it is normally the best option.
Thank you for your time :o)
Hi, i just finished installing my tile approximately 500sqft. B4 i started putting my tile i checked the play of my floor and i knew that theres a big movement of it im talking abt new houses. So i did my grout and everything i used polyblend brand cos thats the customer wants. After 3 days i found some spots that are cracking so i tried to jump on the floor to check the movement and im possitive that every part of the cracked grout has the biggest movement of the floor. Now, i informed my site supervisor and the salesman of the tile that this is the problem why my grout is cracking. Im just worried abt the warranty of my work. Is thre any possible cos of this floor? Is thre any advise that u can give me so i can save my self for a big headache. Thanks
Hey Lan,
The movement in the floor is definitely causing the grout cracking. Unfortunately it is up to us as installers to bring this to the attention of builders, supervisors, etc. before we even begin installing tile. If you can get below the floor joists and add support to the span in order to stiffen the floor that may be enough to prevent further cracking. One way or another the only way you will prevent future problems is by shoring up the floor to make it stiffer.
If there is visible movement it is possible that the floor did not have the required L360 deflection ratio required in most new construction homes. If that’s the case you may be able to get the builder to fix the floor support and you can simply regrout.
Hi Roger,
Is there a better condition for applying grout? like ‘humid and damp’ or ‘dry as a bone’? Also you don’t mention bouncy floors as a cause for grout cracking (other than the pogo stick). Is this possible and what is the fix?
Sara
Hi Sara,
A mildly humid room between 60 and 75 degrees is ideal, as is covering your grout installation for a couple of days to prevent rapid moisture dissipation. Bouncy floors absolutely cause cracked grout. The only fix is to ensure your floor has the proper deflection (the measurement of how much your floor bounces under load) to support your particular installation. It just needs to be built strongly enough to support your tile without excessive movement.
And no pogo sticks.
Any progress on the deflection issue you talked about briefly? I have been sucked in to reading all of the fun we novices have with our projects and have not been able to find anything other than pogo stick references. I am putting in a walk in shower on the second floor that has 2 X 8 floor joists on 16″ centers over a 11″ 6″ span and need to know how to determine if it is enough to support the additional weight of the tile and sub structure.
Hey Scott,
Your floor structure has a deflection of about 335. This is inadequate in its current state for tile. If you are installing ceramic or porcelain you will likely be fine adding an additional 3/4″ layer of plywood but ideally cutting the span in half (or down to a maximum of 8 feet) will create a structure stable enough for whatever you want to put on it.
I’m working on the deflection chart but it’s a LOT of information I’m trying to put together in my free time – really don’t have much of that.
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