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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  • Elissa

    Hi, looking for some insight. We have a newly installed kitchen tile floor which has had issues with cracks in the grout since installation in July. We have tried different grout, reinstalled tiles but are still having issues. The current theory from our contractor is that the tiles are moving from The subfloor. We are desperately trying not too pull out the whole kitchen to replace the subfloor. Our contractor had recommended ceramic tile grout as this will allow for some flexibility. Is this a thing? Will this last? Thanks

    • Doug

      Elissa, in 2018 we had the same problem. New kitchen, new kitchen floor, grout cracking all over. Our problem, which might not be yours, was that none of the tiles actually adhered to the mortar. When they went to pop up a tile to see what was going on, it took 3 seconds to pry the entire 12×24 tile up. Eventually we decided to remove all the tiles and the mortar and redo (almost) everything. The cabinets were custom and the counters were stone and it was all too much trouble to take it all out, especially because no one has insurance against this sort of mistake. If they had left the water on and damaged everything, it might have been covered. So anyway, they removed the toe kicks from the cabinets and then pulled up all the tile, breaking some, but it was so loose that a lot actually slid out from underneath the cabinets. We had electric heat, and they had to chop that up and remove the mortar. The subfloor was fine, but they relaid concrete board down and then put all the tile back down. It is god-awful ugly under the cabinets and appliances, but you would never know from looking at it now. We still have no idea what they did wrong, though I suspect that the trainee mixing the stuff didn’t mix it correctly or, more likely, they should have back buttered all the tile to ensure that it adhered to the mortar.

      Ceramic grout came up, but it wasn’t the right solution, and it will mess up the tiles if you try to reuse them. It is more expensive too. They should try to pop up a tile – if it comes up easily, grout isn’t going to help at all!!

  • Kat

    We have tile in our bathroom that was installed 2 years ago. It was a full bathroom reno and there is radiant heat under the tile on the floor. The grout is crumbling around the tiles and some tiles make a popping sounds when stepped on (clearly moving). Installer insists everything was done correctly but the image I have from before I left for work the day they did tile was that i believe plywood on the floor. Unless 1 man is able to do everything else with flooring im thinking they installed on top of plywood. It was 1 guy doing all the tile.
    They attempted to fix it by injecting something between the tile/under but it didn’t work. Now they are suggesting regrouping with silicone grout…..
    At a loss of what to do and what’s right to do