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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Hi Roger,

We’re tiling a 12′ x13′ bedroom with 6″ x 36″ and 8″ x 36″ plank tiles. About 18″ into the room, there is a crack in the concrete slab that runs wall to wall parallel to the doorway. It is at places about 1/8″ wide and looks like there is a piece of plastic in it. Is the a control joint in the slab? Our house is 20 years old so it’s not new concrete. One side of the crack is about 1/32″ to 1/16″ inch higher than the other side for about the middle 8′ of the crack. Should we grind this down to even it out? Also, do we need to put a membrane or Ditra down before tiling? The hallway that leads to this room is tiled. If we have to use Ditra, how do we handle the height difference? Thanks for your help.



Hello, Floor Elf –

We just moved into a brand new house in central Ohio. It was a spec home and we’ve had a number of issues. Three of my bathrooms have ceramic tile floors installed within the last 8 months. In 2 bathrooms, we started seeing grout cracking over large areas of the floor. The 3rd just has a small crack so far. The builder had the flooring company repair the cracks 3 weeks ago. When I was preparing to seal the grout, I noticed several additional cracks. The flooring company is giving differing reasons for the cracking issue – house settling, humidity issues, etc. They were insulted when I told them I wanted a definitive diagnosis. Between this and all of our other issues, I am now also worried that the tile in the showers is installed wrong as well.
What is your take on this? Are their responses valid (and all of this is normal in a new house) or should I be pursuing a real diagnosis? Any suggestions you can provide would be greatly appreciated. I am so worried that there are underlying issues that I will have to deal with when my 1 year warranty has expired. Thank you!



Hi Lisa,

It sounds to me like they are just excuses. A proper tile installation WILL NOT crack, whether it’s put in a new house or a 100 year old house. The ‘house settling’ excuse is one of my pet peeves, and complete bullshit. The house won’t ‘settle’ and move any more when new than it will in 50 years, it’s normal expansion and contraction, which a proper tile installation compensates for. Stick to demanding a definitive diagnoses, even if that requires a third party.

A good way to non-intrusively examine the installation method is to pull up a heater vent if you have them and take a look at how it was installed.



I just bought a house in louisiana the house was build 9 years ago, my ceramic tile in the livingroom and kitchen are lifting and cracking i found out by my home insurance that the floor might need an exspansion joint, but my livingroom is nowhere near 25 feet in lenght or width but i do have alot of loose tile and it was laid on top of the concrete slab



Hi Sterling,

Is there a perimeter joint, or is the tile butted directly to the wall? Because, no matter how small the installation, you always need perimeter joints. Also, over any concrete installation, the expansion joints in the concrete require a soft joint directly above them. That is where the concrete will crack, it will take the tile with it if there isn’t a joint there.



Good afternoon Floor Elf,

I noticed that the floor I put down several months ago in my master bath had some grout line cracks in it around 1 tile and upon further inspection discovered the tile was loose. I cut the grout out from around and was able to pull the tile out whole. Once I did, I was surprised to find that there was no thinset stuck to the tile, not a smear. The tile was dis colored where the thinset was touching it, the grooves from the trowel, but I can’t figure out why it didn’t stick.

Is this a random incident, a common problem, or am I days away from replacing every tile I’ve laid? the tile is a 12×12 basic marble from your average hardware store. Thanks for the help.



Hi Robert,

It depends on how much contact you have with the marble in the rest of the installation. This is why backbuttering your stone is imperative, as is using a large enough trowel. It may be just that one tile, it may not. No way to tell other than waiting to see if more problems develop.


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