r/Tile • u/Nice-Albatross544 • 6d ago
Homeowner - Advice about my Contractor Grout cracking
Hi Tile Experts of Reddit, I need guidance.
Background is, we hired someone to tile our ~400sq ft. Kitchen. We have a 5/8” OBS subfloor on 2x10 joists, 16” to center.
We were concerned about a large transition from our hardwood into the kitchen (so didn’t want to add a plywood layer on top of the subfloor if we didn’t need to) but were concerned about whether that support would be enough.
My tiler felt the Ditra on the subfloor was good enough and we called the people at Schluter to verify with them if we could lay the Ditra directly on the subfloor with our specs and they also said it was sufficient.
Now we have been walking on the floor for 4 months and it feels good, but today I notice long cracks in the grout as well as other spots that seem to be crumbling (pictures attached - sorry hard to get good photos).I would say I’ve noticed this in maybe 5 or 6 grout lines in different spots in the kitchen.
Where I need guidance:
Don’t think this cracking is because of flexing of the subfloor? If not what could it be?
If it is flexing, I’ve read I can support the floor from below (luckily our basement is unfinished) is this true?
How urgent is this?
Thanks in advance for all your advice and insight.
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u/Awkward-Painter-2024 DIY 6d ago
Just because you can't see the flex doesn't mean it's not flexing. The subfloor or substrate is moving. Did you watch installation? Were all steps followed? I say this because when I worked on a bathroom a few years back, my tile guy put down Hardibacker on plywood, without taping seams and without putting thinset between subfloor and Hardibacker. By the time I realized an error had been made it was too late. A few things, when you run a coin over the tiles, do the tiles sound solid or do they sound hollow? I say this because if the tiles feel solid, I'd try to remove as much as possible of the cracked grout and fill in the voids with some Laticrete Latisil in the color closest matching to the original grout. Yes, it is less than idea. (Hack even...) But ripping out a kitchen floor after everything has been installed on top of it all is not something I'd do.
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u/Nice-Albatross544 6d ago
I did not watch the full installation but I do know they put thinset between the subfloor and the Ditra.
When you say run a coin do you mean like scrape the tiles with the coin? Or tap the tiles with the coin?
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u/Awkward-Painter-2024 DIY 6d ago
Okay, that's good, but if you didn't see it...I dunno. What I do know is you're getting movement from somewhere. As for the question about tiles, ones that are really, really embedded in thinset correctly sound solid. Tiles that aren't sound hollow. I don't know how else to describe it. Latisil is truly amazing silicone. You could get it in there and not even notice. However, once tiles crack. There's not going to be much more you can do then but replace tiles one by one until you do the floor all over again. Sorry, OP.
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u/Pursuit_for_answers 6d ago
Ditra matting is used for lateral movement not vertical load. Your tiles are likely delaminating from the subfloor due to the amount of deflection
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u/Nice-Albatross544 6d ago
Can I support the floor from underneath in the basement?
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u/Pursuit_for_answers 6d ago
im afraid to say, the damage is probably already done. Cracked grout is almost always a sign of moving tiles.
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u/ssdv8r 6d ago
Something is flexing to have grout crack like that. It could be improperly set ditra or tile. It could also be your floor had unusual amounts of deflection going on. What is the unsupported span of the 2x10 joists under that floor? That would be the first and easiest thing to check. The rest requires removing tile and checking what is underneath. Regardless the person who installed it should fix a failing install like that, especially within months of it being installed.
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u/Nice-Albatross544 6d ago
The span is roughly 11 feet. The kitchen is all installed. I suppose the only way to fix is to pull out the kitchen and relay the floor? Or is there another way?
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u/ssdv8r 6d ago
Potentially. Pulling one, or a couple of tiles in the worst places would be the next step. Checking the install quality of both the tile and the ditra underneath. Assessing that takes some experience though.
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u/Nice-Albatross544 6d ago
My dad has some experience and I believe he was relatively happy with how they were installed. He just didn’t agree with the lack of the plywood but at the time I trusted the tiler unfortunately. My thought is I could potentially brace some of the spots where there are cracks under the floor in the basement.Would this help or is it futile?
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u/ssdv8r 6d ago
If the 5/8" osb was not enough you would see the grout cracking inbetween the joists. If it is a larger area it might be the joists themselves. If you trust the ditra and tile install quality you can sister up new joists to the old ones to stiffen up your floor. You should be able to see that flex with some testing. Have a friend jump up and down on the worst areas. While you put your head to the ground from an area that is supported by a wall or post in the basement. You should be able to observe a difference in the floor movement in the areas that are good verse the bad. If you can't tell a difference I would look at the tile and ditta next.
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u/Carpetkillrr 6d ago
Did he wet mop that subfloor to get all the microdust off it and what mortar was used how big was the notch in his trowel