Foundation, Slab Leak, or Crappy Tile Install?

Over the past week my wife and I noticed a creaky floor tile in the kitchen. Our tile is 12" porcelain installed by the previous owner. Wasn't a huge issue, just an annoyance, so I didn't think much about it.
I came home today and noticed a distict bow in the floor where the creak had been. At the highest point, the floor tiles had popped up, raised a half inch (almost like the tiles were being pushed together and therefore must flex upwards), and were mobile. The grout was intact between the tiles but had released where the tile met the wood cabinet.
I grabbed my grout saw and was able to remove six full tiles and the two half tiles where they met the wood cabinet. I only removed the mobile tiles. All of the tiles came up intact and without much force.
Underneath I found a hairline crack in my concrete slab. I've cleaned the crack and cannot even fit a needle or slip of paper within the crack at any point.
Tomorrow I am having a plumber come out to validate that I don't have a leak. So by this time tomorrow I should be able rule out a slab leak.
Then I have to decide if I want a foundation company to come out and have a look at the slab.
While I am waiting and doing some research, I found that most of the material used to adhere the tile to the concrete had come off with the tile. Very little remains on the concrete. After going through my kitchen, entry way, and hallway, there are a number of tiles that ring hollow as though they are not adhered. The only thing completely preventing me from proclaiming that it was just a crappy tile install is that many of the "hollow" tiles seem to follow a line where the crack could go. There are a few that don't, but many do.
I'll keep everyone posted but in the meantime, has anyone had a hairline crack in their slab (one that is so small not even a slip of paper could be inserted) be something substantial? My fear is that both the plumber and foundation repair person will say there is a problem and I'll be out thousands when it was really just a crappy tile install. Feedback is welcome.
John
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No direct experience here, but as an armchair speculation, if the slab settled into a very shallow "V" shape, it might result in what you are seeing. Such a crack may have its fulcrum at or near the floor level, and stay "closed" looking at the surface, widening with depth. Such a deformation would tend to crowd the tiles, put them under compression, then pop the mortar off the back, leaving some tiles in a little hump. Such a settlement would not indicate a poor tile job, but rather reflect the fact that all tile and mortar are practically inelastic, and pop off or break under stress. The continuing line of hollow sounding tiles is worrisome. The age of your house is a factor. If new, it would suggest slab settling due to recent moisture changes or incorrect foundation structure. If older, the tile work may have been applied to conceal a pre-existing crack, for purposes of sale. For your sake I, too, hope it is a bad tile job, or at least solvable without spending a huge amount. Best of Luck.
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All slabs will get cracks . What makes you think you have a leak if you don't see water. What will a Plumber do ? say he see's no water? ( waste of money) It sounds like a bad Tile job
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Tape a piece of plastic to the slab. If no condensation forms you have the dryest slab in the world and you can blame the installer. If a little forms then it would have to be taken into account before any repair.

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Sounds like the guy that was using drywall mud to put is tiles down in the bathroom.
I will bet piss pour installation from the installer.
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John Hill wrote:

How old is this house? It doesn't sound like a problem to me. A hairline crack in concrete slab is common. What will a plumber tell you? Oh yeah, lets break out the jack hammer? Think you need to relax. You said the owner did the tile job? Well then that's probably the problem. Most homeowners use the cheapest tile adhesive or thinset available, and that's usually the problem. You get what you pay for.
Can't imagine a problem with the amount of thinset on the back of tile unless he used the wrong notched trowel, which could be a possibility. I would just remove the tiles that are loose and reinstall as long as the slab is flat and true.
It's common on floor tile to hear the hollow ping when something is dropped on it. I just keep my fingers crossed none crack when there tested that way.
Calm down relax and don't get your panties in a ruffle, sounds to me like everything is fine.
California General Engineering Contractor Retired. License # 707455
Rich
--
"you can lead them to LINUX
but you can\'t make them THINK"
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The plumber came in this morning and did a supply line check. No issues. He mentioned that it looked like a crappy tiling job.
Spoke with a foundation company and after the obvious questions (are the walls cracking, doors/windows sticking, etc), they said the foundation sounded fine. They admitted it may have shifted a bit but not settled or cracked. They could schedule someone in February to come look at it if I wanted. I declined.
Spoke with a tile guy after all that, and he stated he's been getting more calls this week about tiles popping than in the previous weeks.
Therefore, I reached the conclusion that the tile job was crappy. Thankfully, that will be the cheapest of the fixes.
Thanks for everyone's input!!
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