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.

Previous post:

Next post:


We have grout coming out for the 5th time..We hired the floor in our kitchen done by a contractor, who is no longer in business, and the section by our sink keeps coming out. My husband has removed the tiles and screwed the cement board down every 2-3 inches and put glue all over the tiles.



I’m seeing cracks in the grout along the edges of various tiles. The adjacent tiles appear to be moving (loose). The tile is about a year old, installed over a crawlspace with a 3/4 inch plywood subfloor with 1/4 inch cement board over that. However, the installer didn’t use mortar under the cement boarda although he did tape and mortar all the seams and he screwed the cement board directly to the subfloor, about 56 screws per 3×5 sheet. We plan to remove and replace the grout and loose tiles next week. Do you believe I will continue to experience these issues because mortar wasn’t used under the cement board? Thank you for your time and assistance.



I had porcelain plank tile installed for a upstairs bathroom floor. The plywood floor was screwed down, and ditra mat was adhered with thin set. It has been 4 months since install, and i looked at the grout closely and there are now small hairline cracks running the length of the grout along the tile edge. This is happening in about 50% of the grout lines. Any suggests on the cause of this, and what can be done to fix it. Thanks a lot in advance, great blog page! :)



It’s the contractor, I’m pretty sure roger will tell you it’s the install of the substrate, it’s the contractor’s fault.

I had the same thing happen. I had the contractor come out three times to repair, it didn’t work, ridiculous repairs.
I asked another contractor for a bid & asked him to pull out a tile & investigate, sure enough, no adhesive between floors, no adhesive on joists, sheet rock screws used every 2-3 ft., the list goes on & on.

I sent the contractor an email telling him I was prepared to do the following if he didn’t return all my money including the tile. I had already started a file with Angie’s list, so he had that when I sent him my email, even though he wasn’t listed. It was threatening & maybe he realized I would follow through on the following. It worked, I got all money returned.

Department of Labor & industry (formal investigation)
Licensing Board
Angie’s List
American Arbitration Assoc.
Consumer Protection Board
Filing complaints & issuing bad reviews
Small Claims Court or Hire an Attorney
Contractor Recovery fund



Thanks KP,
We now have the tile store manager where we purchased tiles from coming out later this week to home to inspect cracking tile and grout. When I asked him for a copy of receipts of purchase, he also expressed concern and wanting to come see cracking. Explained to him that within 5 months my new floor should not be cracking and at this point since it is extensive, it is a demo & redo job, and not a patch up job. Thinking the Tile store usually does not want to throw a tile contractor under the bus, but in the meantime wants to cover their tail. Told him will hold someone accountable.



Cracking everywhere!
Had a company install approx 490 sqft of porcelain tile (12×12 and 12×24), in two joining rooms (kitchen and morning room) less than 5 months ago. He highly suggested using Latacrete Strata Mat instead of Wonderboard, Durrock, or cement board. He said they use mostly this new method, and especially better for our rooms. They installed this on top of what I believe is 3/4 inch OSB.
Two weeks ago (early June), wife noticed one cracked tile. Couple days later we noticed a couple more. Now few days later, we actually get closer and notice approx 6 cracked tiles, 30% of grout having cracks, and one even moves when step on it.
This is unacceptable with amount of money spent. I hired tile contractor because this is not my line of work and therefore relied on his suggestion & skill. What type of warranty is usually associated with this? At this point, who do you suggest I contact first: tile installer, tile store, product manufacturer? I don’t want them to play the blame game. Thanks.



Hi Joe,

That is unacceptable with any amount of money spent! I will say that strata-mat is an excellent product, and this is not a problem when properly installed. It will end up being a problem with the installation of it, I can nearly guarantee that. However, I would begin by calling laticrete and getting a rep to come out. He will be able to tell you exactly what is wrong with it, that way when you do contact the installer you know exactly what was done incorrectly.


Crystal E

Hi there, we just had a couple of guys install new porcelain tiles on our kitchen floor. They said they knew how to install tiles. They did the job a week ago, starting Friday, and finishing Saturday evening. They told me we needed to keep off the floor till at least Wednesday to allow the floor to cure. So, we did that. Then my husband begun to prep our walls for painting in the kitchen, mudding, & sanding spots on the walls. So I used our vacuum, with the smooth floor attachment to pick up the dust over the tiles. (This doesn’t use a roller or moving bristles of course.) I had cracking grout lifting up out from between some of the tiles. I got down on my knees and starting closely inspecting the job, and realized there are several spots around the floor that have grout cracking. There is Wonderboard underneath the tiles. We have a wood subfloor, and to be honest I don’t know if they did apply thinset under that Wonderboard, before they screwed that into the wooden subfloor. I took some pics on my phone and sent one of the guys who installed my floor a text showing him huge missing pieces of grout lines and chipping, telling him all I did was run my average vacuum over it and the dude was like, “OH, you can’t vacuum the grout and tile.” One side of our kitchen connects to a dining room that was carpeted. The guys didn’t take back the padding, and tiled about a good three inches over the padding. They didn’t cut the Wonderboard either to ensure it laid underneath that whole row of tiles, which spans twelve feet, twelve tiles long. I know that the Wonderboard is completely missing at least 3-4 inches under the edges of those tiles, and that is where the major cracking began and grout coming out completely. The day they finished, I asked why they hadn’t taken up the carpet padding and tiled over it instead of taking it up… It concerned me. Now that concern is a reality. Won’t they have to remove tiles, that padding and cut more Wonderboard to go completely to the edge of our tile, in order to fix this? This one guy who was involved in the installation said he would just “fix” the grout… But after a close inspection all over my flooring, I see more grout cracking at corners and along edges even into the middle of the floor. Is it likely we just got a really sucky tile job that has to be ripped up and started over again?



Hi Crystal,

Unfortunately yes, you apparently had hacks installing your tile. Tiling over carpet pad??? WTF? I wouldn’t trust a damn thing they did. And waiting four days for it to cure – the only thing you’d do that with is mastic, which shouldn’t be used on your floor. A total replacement is very likely the only solution.



We installed tile to our bathroom floor. There is one tile that is moving a little since it was installed in front of the commode. Will this piece need to be removed and retiled or is it just not cured yet? It’s been 24 hours since installation.
Thank you for your feedback in advance.



Hi GT,

If it continues to move you’ll need to remove it and reinstall it.



I have a two week old brand-new shower and the grout is cracking from corner to corner on the line to the bottom of the tile contractor who refused to come out to repair it says that it’s normal and happens from time to time



Hi David,

Do you mean there is grout in the corners and it’s cracking? If so then it’s because it should be silicone in any change of plane, not grout. If it’s cracking on the floor or on the wall in the field tile that is indicative of underlying movement and/or improper installation.



common sense tells me you cannot use grout caulk to fill in for missing shower floor grout. for one, caulk would stick to showerer’s feet. correct?



Hi C,

You’re correct, but not because it will stick to someone’s feet. Because it will eventually lose elasticity and become unbonded from the sides of the tile, leaving a cracked ‘grout line’. It simply will not last.


Deborah Woodhouse

We have a keyway that installed in our newly built two year old home and since we have experienced bulking in the tiles in the floor, when we approached the builder he explained that the keyway is to help expand and contract minimize cracking and does not affect structural strength.

What things should I be concern about years from now about the tiles or flooring? Can this damage cause us undo heartaches later and a lot of expenses on our part to have tiles or floor replaced?

What should I be looking for or asking the contract to cover in a letter for future problems with this keyway not being installed correctly in the beginning?

We just know what to do about this situation.

Thank you, in advance for all your help in helping us get this issue resolved with out builder.



Hi Deborah,

If you’re referring to a soft joint as a keyway, then he is correct. They are required as an expansion joint both at set distances in installations as well as over any expansion joints in the concrete slab. This should explain it better for you: Soft joints


Leave a Comment

;) :wtf: :wink: :whistle: :twisted: :suspect: :shades: :roll: :rockon: :oops: :lol: :lol2: :lol1: :idea: :guedo: :evilb: :evil: :eek: :dance: :cry: :corn: :cool: :censored: :bonk: :arrow: :D :?: :-| :-o :-P :-D :-? :) :( :!: 8)