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 Dave! I’m so thankful I can across this very helpful site!! My husband and I moved into our newly built home about a year and a half ago. He pointed out a small crack (smidgen bigger than hairline) in the grout of our guest bath between tile and the bathtub. The tiles themselves are fine and there aren’t any cracks in the grout between tiles, just near tub. He gave me the job of figuring out if this was really bad and needed fixing. I know nothing of construction!!! Does this sound like something needs redoing or is it more cosmetic? Thank you so much in advance for your advice!



Hello. Our home is 16 months old. We have porcelin rectified 18 inch tile throughout. During first year we had 3 cracked tiles (diagonally from end to end ) in different rooms. There was also a problem with grout..it was too high in places, too gritty in others and in several spots there were pieces missing. Tbe builder had the tile contractor make all repairs. Within a couple of months.. we now have 3 more cracked tiles (random areas) and Tbere are pieces of grout missing through the house. Tile contractor states that cracked tiles are from cracks in foundation which is normal for new construction and no longer warranties since the 1 year period is up. They have not made a determination as to why the repaired grout is once again “disappeating” in spots all over the house! HELP!



I live in a condo on the beach in Florida. The floor is total tiles and evidently by what I’ve read, installed without expansion joints. When it gets cold out tile pops, tents, and sometimes cracks the grout. When walking on it, I hear crackles. I’m heartbroken. Needless to say I can’t afford to retile 2700 sw ft…. :(



My Home entry to Kitchen from Hallway, approx 2*4 tiles in line jointly lift & Lost base Surface. coming popup. What could be primary reason.
Thanks In advanced for your experience comment or neutral answer.



Please help! I moved into our home 3 years ago, a 20 year old cape cod with ceramic tile in kitchen, adjoining hall and bath, approx 200 square feet. There were a few cracked tiles that I had a tile guy replace with some I found in the garage, but now I have a LOT of tiles with hairline cracks, most are Y shaped beginning in the center, and there are areas where there are several tiles cracked but the crack doesn’t run in a line through them… am I making sense? I can see at the basement stairs where the tile floor ends that there is cement board (?), gray with a mesh looking bit to it. Looks like it sits on the osb subfloor, I cant see any thin set that oozed out between, but maybe I wouldn’t?? There are places where I walk and can actually hear the floor squeak I think, under the tile. Oh and I don’t know how long this tile has been here, only that it was installed by a previous owner. I am a single mom with a very very limited budget and I am a bit overwhelmed. Who do I call, a tile person, a contractor, my Dr. for Valium? I am guessing part of the tile needs to be pulled up down to the subfloor to see what is going on.. Sorry for the length of this, and BTW you are a riot.



There is alot going on and sounds like it was not installed at all correctly and needs to be pulled up and start over and done correctly, sorry



only one straight line of cracked sanded grout across the 9′ length of bathroom. The width of the floor is 4′ and the crack is parallel to the long side 4″ from the wall.
bought the house with 15 year old reno already done . bathroom floor is 2″ tiles in sheets, attached with unknown mortar or thinset. Under that is 5/8″ plywood over probably 3/4″ subfloor. I am remodelling the bathroom with new vanity and toilet and they were out when I discovered this crack. I cannot see any movement when I step on that area but I don’t know how the plywood was attached to the subfloor. I was not planning on replacing the tile floor. Since the floor is now clear, would it be unwise for me to just repair the grout or should i pull up some tiles to check the mortar or thinset? or worst case, how do I know if I should really be replacing the whole floor ? thank you in advance. It is fantastic that you share your knowledge with everyone.



Sounds like they didn’t leave an expansion joint along the outside of the wall what I would do remove the base board and if there’s grout along the outside of the wall remove all of it and then go back and repair where the crack is by removing the grout and putting new down , dk


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