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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My grout is cracking from loose tiles. Come to find out, the previous owners tiled over an existing tile floor. One by one they are starting to lift. How can I stop this domino effect without removing them all and starting from scratch?!



Hi Jennifer,

Unfortunately you can’t. A tile installation is only as good as what’s beneath it. That includes the underlying tile as well as whatever they used to bond it. Apparently something isn’t correct, that means it will need to be removed to properly rectify the situation.



It’s a waste of time and money,rip it all out down to main sub floor ,put half inch cement board in cut it all in then mix thin set up mud down cement board,set tile an grout do it right the first time, your floor is history start all over……..



I am hoping maybe you can help. I had tile flooring installed throughout my entire house in June 2015 – 18″ tiles installed with 1/4″ sanded grout lines onto concrete subflooring. Within a few weeks, the grout in the living room had started to chip in several areas from my dog’s nails and furniture movement. The chipping starts as flakes of grouting coming off at the surface and then eventually the entire grout line is gone. The installer removed and replaced the grout in the damaged areas. However, the problem has persisted and is getting worse, with new areas having problems now months after the tile has been installed. The problem is only in the living room. After the second grout repair, in some areas, the grout will practically dissolve if it gets wet, but it’s only in some areas that were replaced. At this point the grout has been removed and replaced three times in damaged areas through my living room (basically everywhere that is not covered by rugs or furniture). I have asked the installer if improper thinset is the issue and the tile is moving. Of course they deny it. The installer has pointed the finger at the grout manufacturer, while the grout manufacturer says it’s because my dogs were allowed on the tile before the two week curing period was up (which we weren’t informed of, but that’s a side issue). However, my dogs being on the tile does not seem like the problem since my dogs are active throughout the house and not all areas are affected. Also, some of the areas didn’t start having problems until months after the tile was installed. Other rooms that were installed at the same time are not affected either. Frankly I am at a loss for what could cause such widespread damage in one room, but not others. Can you offer any insight into what might be the problem?

Other information that might be helpful: The area affected was previously covered with carpet. The concrete in the living room did not appear to have any damage or discoloration different from any of the other rooms of the house. Large cracks in the concrete were repaired in all affected rooms, including the living room, with some kind of hot pink/red paint on product. However, damage in the living room extends beyond the area painted and other rooms where the product was used are not affected.

Thank you in advance for any help or insight you may have!



Hi Roger
I installed tile 30 days ago In a “random” pattern using 6″,12″,&18″ square role. It’s gorgeous, but I have ONE f*#*#*g 18″ inch piece which is naturally in the highest traffic area in the center of the passage to the bedroom which is crunching when I step on it, and the grout is cracking. How do I remove, clean out the thin set and reset it? I used Ditra underneath and I am sure it will be rock hard with all the little squares filled in with hardened thin set now. I am sad?



Hi Sally,

Scrape the grout from around the tile, get a utility knife and cut around the tile into the ditra and remove the tile and ditra together. Replace the ditra and tile after scraping all the excess off the subfloor.



Thank Roger.
You ARE super cool.


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