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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  • oleg

    Hi Roger,
    I’ve learned a lot from your articles, especially the one most relevant to my situation: Here is my situation. I remodeled the kitchen a year ago, installing new cabinets and tiled the floor with 12×24 tiles. Grout started cracking when we started using the kitchen in a few days after it was done. Few weeks later we noticed that the floor was crunching as we walked on it. Some tiles also moved up-down under pressure, even though very slightly and when pressed in the corners. We re-grouted the entire floor 3 months after, cleaned the original grout completely and re-did it. By now, the grout cracked / flaked around all tiles where we walk (in areas less walked it is still intact). Few spots became totally grout-free, crunching sounds and tile movement increased.

    When the contractor tiled the floor, I saw him screwing in sheets of wanderboards to the subfloor, then putting thinset and then tiles. But when I talked to him about this problem, he admitted that he did not check subfoor for deflection before starting the job…ouch!!! I would remove the tiles and check the subfloor. But if it is, in fact, deflection issue what can I do ?! I can’t raise the subfloor because the new kitchen is sitting on it! This is what I am thinking, Roger:

    1) Remove few tiles first and see if there is defective (patchy) thinset issue (best outcome) or subfloor issue (worst outcome).
    2) If this is just thinset, then I would remove tile, clean thinset and retile the floor.
    3) If this is subfloor, is there any type of grout (perhaps with addition of polymer/latex) that I can use to stop this nightmare? The spacing is 1/8. I know it is a long shot, but perhaps there is a hope. I can’t resolve the deflection problem without removing the itchen cabinets – and this is something I am not willing to do.

    Thanks for your advice Roger…sorry for long post.


  • Laura

    Hi Roger,
    My husband started remodeling our master bath but after he did half the shower wall he decided it was too big of a job for him to handle. Esp since he’s never done tile before. We called in a contractor to finish the job. There were several different workers and some would come one day, some the next. It took them about 2 weeks to complete. The contracter himself was only here the first day and seems like one other day after that. None of the workers spoke english or even understood it.
    So asking questions was impossible.
    My husband still needed to finish the sheetrock and paint and we had planned to do that before we sealed the tile. This has been a several month project waiting on the shower and tub and my husband only having 1 weekend a month off. We were finishing it this weekend and noticed the cracks in the grout. In many places in the bathroom. A day or 2 after the workers left we noticed a few holes or cracks in the grout around the splash wall of the tub. My husband dug it out and re-grouted those few small spots.
    Now that we’ve found numerous cracks all over the bathroom we feel the contractor needs to fix this. When we called him yesterday (Thurs) he said he couldn’t come until Monday. He also said we needed to get the caulk the same color as the grout. We have that already as we purchased everything prior to hiring a contractor. They also cut the tile short in places around the edges of the room stating the baseboards would cover it. He even left a 2″ gap from the edge of the tile to the wall stating the vanity would cover it. Which it doesn’t, but that’s beside the point.
    So my question is, what is it that needs to be done. We spent about 6k on the tile grout backer board etc and all of that was prior to hiring a contractor. I’m so afraid he’s not going to really fix it like it’s supposed to be. Here are a few of the cracks in the floor grout. Of course these cracks run the length of the tile. Excuse the sanding dust.