Why is my Floor Grout Cracking?

by Roger

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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Lucian

Hello Roger. # weeks ago i contacted someone to install floor tiles on my bathrooms on the second floor of my house. In one of the bathrooms ,we remove the linoleun and the playwood underneed,then we put a cement sheet barier ( if you can call it that way) after which he installed the tiles.
The next bathroom he decided not to remove the existing linoleum,and start instaling the tiles on the top of linoleum.Only 3 days later the Color grouth start to crack,now is about 50% from 40 feet size cracked. What can cause this to crack?? I said it might be because he installed over linoleum,instead of removing it,what do you think?? Now he refuses to come and fix or remove and reinstall,and i paid 5.00$ per sq.ft to install. I paid cash,no receipt,what should i do ? Thank-you !

Reply

Roger

Hi Lucian,

I have no idea what you can do to remedy the monetary issue. Your floor is cracking because it was installed over the linoleum and does not have a proper substrate. It will need to be replaced. Sorry, that’s all I have the ability to help with. Maybe contact your local building department, they should be able to give you options.

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Sam

I have a new house built (approx 4k sq ft)within the last two years in Fl . I have tile ( random sizes from 6×6″ to 12×24″ and a variety of sizes in between )on the slab throughout 75% of the house. Within 6 months or so I noticed hairline cracks in the tiles and grout on every saw cut seam. Turns out a cheap underpayment was used and not Pro flex. The builder replaced the tile on every saw cut line and laid down Pro flex as the underlayment making sure there was at least 6″ on each side of the saw cut. Here we are about 5 months out from the fix and I noticed hairline cracks in the grout ( not the tile yet) along almost every saw cut line. There are six or so tiles in different spots that are actually loose – not cracked. When the original tiles were removed I saw every area and there were no cracks in the slab. Any thoughts on what might be happening and how to fix correctly?

Reply

Roger

Hi Sam,

Yes, a soft joint HAS to be installed through the tile installation over saw cut or relief joints. Cracking grout and tile is why. Placing pro flex over it only allows you to move it two inches one way or another, but you still need it. That’s where the slab cracks, it’s designed that way. The tile directly above it will flex, if a soft joint is installed – it’s designed that way. :D

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Cindy

Roger,

Four years ago I had a bathroom remodel done in the master bath of our then 15 year old home. I had no problems with the tile floor or the tile that surrounded the tub or the grout in either location cracking. We had a SunTouch heat matt installed to warm the floors. New sub-floor was laid, then the SunTouch (no Ditra) by the primary remodeling company (considered “high-end” in our area). A different company laid the tile after the SunTouch mat was installed. As summer started, we noticed some slightly loose tiles toward the end of the first full summer. Once we turned the SunTouch heated floor on in the fall, the looseness dissappeared–until the following summer. The tiles are loose enough that you can feel them shift and the grout has come out–this is only in approx. 1/3 of the bath (an area 3′ x 10′). I have had the area re-grouted, but we have the same problem each summer when we turn off the SunTouch floor. Installers have indicated there heat mat caused a expansion movement that the thinset could not tolerate thus loosening the tiles are have offered no solution. Any suggestions?

Reply

Roger

Hi Cindy,

How long was the time between the tile being installed and the heat being turned on? You normally have to wait at least 21 days. Regardless, something was done incorrectly with the tile installation. It could be inadequate support, improper coverage or the incorrect thinset. The tile will need to be replaced, what is (or isn’t) on the back of the tile once it’s pulled up will likely tell you what the problem was.

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moira duncan

We have tiles fitted in our bathroom (quite a large bathroom). An under floor heating stretch mat was put in , obviously before the tiles were laid. The grouting has been redone four times so far as it keeps coming out. Is there any way this can be rectified without having to get the whole floor taken up and replaced?

Reply

Roger

Hi Moira,

How soon after tiling was the heating turned on? I believe the problem lies with the cure of the thinset (or lack of). The grout is not the problem, it is the bond of the tile to the substrate creating movement, which is causing the grout to crack. I would need specifics on how the floor was constructed to give you a viable solution, but most all of them require removal and replacement of at least the tile.

Reply

kelly

Hi Roger,
I took out the tub in my bathroom. The existing tile was laid directly on the concrete floor, right up to the tub. After I took out the tub, I expanded the room by 2 more feet beyond the tub. The result of that is that I have new concrete fill where the tub was, in between two smooth slabs. I know you don’t think tile should be put directly on concrete floors, but if I put down ditra under the new tiles, they will be higher than the old tiles. The only way I can see to keep everything level is to put the new tiles directly on the concrete. But, do I need to do anything where the “fill” concrete meets the old slabs? Is it likely that the fill will expand/contract differently from the existing slabs? Thank you.

Reply

Roger

Hi Kelly,

You need a soft joint between where the existing floor ends and the new begins.

Reply

Kathy

We moved in this house 7 months ago, and just recently, as in the last month, there are all these white places in the grout, where it looks like it is being chipped out. The rest of the grout is dark from dirt, so I know this is more recent. I make my own tile cleaner with 3 cups water, 1/2 Tablespoon peroxide, 1 Tablespoon vinegar, and 1 drop tea tree oil. Could any of those items be affecting the grout.? I heard white vinegar can soften grout, but I didn’t think 1 tablespoon per bottle would affect it. Any thoughts? Also, the places are in a 6 yard X 6 yard area, not the rest of the house (4 other tiled rooms), which makes me think it is not the vinegar.

Reply

Roger

Hi Kathy,

It is not the vinegar. It is more likely an inadequate substrate beneath that area, leading to movement, leading to cracking and chipping of the grout. If the rest of the grout is dark from dirt – two things:

1. The lighter areas you are seeing are likely the original grout color.

2. If the grout is dark from dirt you need a new grout cleaner. :D

Reply

Linda

Can a flood cause grout to crack?

Reply

Roger

Hi Linda,

No. But a flood can cause the underlying substrate to swell, which will crack the grout. Water will not affect the grout at all, movement in the substrate will. So technically it does not cause the grout to do anything, but it will cause the substrate to swell, cracking the grout.

Reply

Char Farner

My new bathroom was finished less than a week ago. A tile floor was installed where there was linoleum. Yesterday, I noticed the grout between the floor tile and the tub is cracking and coming loose. Should I call my contractor back to fix it? I don’t know how to fix it myself. It has to be trouble with the way they installed it, doesn’t it? I tried to attach a clear picture of the problem, but I wasn’t able to, unfortunately.

Reply

Roger

Hi Char,

There should not be grout between the tile and tub, there should be silicone or caulk. The grout needs to be removed and replaced with the proper product. Yes, I would call him back, that should have been done the first time.

Reply

Linda

A pipe under my kitchen sink detached and caused a flood throughout the first floor of my home. The tile in my house is 14 years old. I have always had a problem with grout cracking and hollow sounds under many of them. My question is, is it ok that that tile was sitting under 1″ of water for a few hours, should it be replaced? One spot the gout broke out completely and there are long several cracks down several of the gout lines.
Thank you!
Linda

Reply

Roger

Hi Linda,

The tile and grout won’t be affected by the water, your substrate is the problem. When water got into it it caused swelling, which caused the tile to move, which caused the grout to crack. It does need to be replaced, but it’s the substrate beneath the tile that is the problem.

Reply

Betsy

Hi Roger – this is an interesting post. I have long assumed the problems with my tile cracking were due to the installation. The contractor installed a new subfloor, then electric underfloor heating. He put a layer of mortar on top of the floor heating mat, then installed floor tile on top of that. He also installed tile half way up the walls of the bathroom. Within a few months of the installation, I noticed small hairline cracks in the floor and wall grout. There are no loose tiles. I notice the cracks and although I don’t know if anyone else would I think a home inspector would probably see them and question the quality of the installation. Is there anything I can do to improve the appearance of these small cracks, such as applying a thin coat of grout over top of the cracks? The cracks are mainly in perimeter of the room (where the floor joins a wall, tub, or other vertical structure) and where ever there are corners.

Reply

Roger

Hi Betsy,

If those are where your cracks are then your installation might very well be just fine. Any change of plane requires caulk or silicone, not grout. Different planes will expand and contract in different directions. Silicone can compensate for that, grout can not.

Reply

Shirley

I have some grout that is cracking and you are right, the reason it’s cracking is because the tile is moving. In fact, the tile comes right off. I also see that the tile was installed over K3 or particle board which was installed over the plywood. The tiles were fine for 2 years before the cracking appeared. Can I just try and reinstall the 2 tiles by making sure there is plenty of mortar under the tiles?
Thanks,
Shirley

Reply

Roger

Hi Shirley,

You can, but you’ll be replacing them, along with more cracked tiles, sometime in the near future. Your floor is built improperly, there is no fix short of replacement.

Reply

Joyce

i had a ceramic tile floor installed over a wood floor. there are spots where the tiles are cracked and the grout has come out in chunks between many tiles. You can feel the floor give in some spots. Can this be fixed or should i just replace the floor with something else which is what the contractor recommends.
Thanks
Joyce

Reply

Roger

Hi Joyce,

Something needs to be replaced. How much of something and specifically what depends on the reason your floor is cracking. In nearly every scenario it is improper substrate preparation, which calls for removing existing tile and floor and rebuilding properly.

Reply

Curt P

Further to my grout cracking, what about a flexible grout such as Quartzlock2?

Thanks again

Reply

Roger

Hi Curt,

Again, I’m not sure which grout cracking you’re speaking of. Quartzlock 2 does not have significant flexibility properties either.

Reply

Curt P

Hi Roger,

Yes, it is bonded to the plywood and was backbuttered everywhere.

What about a urethane grout as I’ve read they have a decent amount of flex?

Thanks

Reply

Roger

Hi Curt,

Urethane grout does not have any significant amount of flex. Beyond that I have no idea to what you’re referring as you have not typed this as a response to my (assumed) question or answer as instructed above the little box you typed this in. I have (literally) over 20,000 questions here, I can not memorize every person’s project. :D If you can ask again as a reply in the proper place I can probably help further.

Reply

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