We had a contractor do a refresh on our kitchen. Generally, they did a good job. They moved some cabinets, installed a new range, painted and installed a new ceramic tile floor. It looks-- or looked beautiful.

Now it's 9 months later-- and cracks have begun appearing in the tile-- running the length of the kitchen. The tiles are large tiles-- 20" x 20" each, with a very thin grout gap between them. The floor was floated flat before the tile install, but there wasn't any liner or anything put down, the thinset was applied directly to the floated floor.

What's curious is where the tiles have cracked-- they've split about an inch or two from the grout. My understading is that the grout is supposed to be the stress relief point-- so any crack should appear there, not the tile.

Any thoughts? I'm not a flooring expert at all.

The contractor has agreed to fix it--- but if they're going to fix it the same way, I have a real fear I'm going to be looking at fresh cracks in another 9 months.

I can provide more information-- I'm just looking for answers to this curious cracking.

The larger the tile the wider the grout line
Needs to be hope that help

find a wire or pipe coming up from below into the kitchen, and measure the depth of the subflooring. general recommendations from carpenters and tile wizards in the past indicate there has to be 5/4 inch solid underlayment before you can put down tile.

the generally recommended method for tiling is to set a minimum 1/4 inch tile board or cement board in thinset for an inflexible base over that solid subfloor. at that time, you can set the tile with thinset. an alternative is to use Kerdi brand floor mat over that solid subfloor, thinset to the floor, thinset to the tile, which provides full isolation.

if neither was done, and you are, say over a layer of mud over a slick floor, you are at the mercy of the subfloor. wood moves with temperature and moisture. any tile put over that substrate is going to crack on the joist lines, and often the grout will start cracking out first, then the tiles.

SWSCHRAD:

I'm going to check under the kitchen and find where the joists are-- It sounds like they set the tile directly on the floated leveling mud, I'm betting the crack is right along the joist. They skipped the mat/cement board step, which, if I'm understanding correctly, isolates the tile from the wood sub-floor.

This would explain the hairline just about 1 inch from the grout line, and it runs pretty much the length of the kitchen.

I'll report back tonight when I get home and inspect it.

There are other methods than backer board but there does need to be something to isolate movement between the subfloor and the tile. Backer board works. Schluter underlayment and thinset will work. There is a poured epoxy tile underlayment that will work. Whatever is there, there must be something other than tile on a leveled plywood subfloor.

Even if it was done correctly, it's possible that there was some framing deflection that caused the cracks. This is much more common with larger tile. The floor may deflect within normal bounds 1:360 but since the tile is so large, that small amount of flex can become a significant measurement over a 20" tile. Your problem is likely some deflection due to a long span or a raised and/or moving joist.

Since they are coming back to fix it, let them do so. If you are curious then you can see what was there when they start taking tiles out. With one fail, they certainly do not want to be returning again so give them a chance to fix it right.

With tiles that big that floor needed to be 100% flat and 0 deflection.
One low or high spot and it will snap the tile.
If they had of used smaller tiles, even if it was not preped right it may have worked.