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This floor is in my bathroom. Under the house it looks like this floor rotted out and the previous owner replaced the plywood subfloor and then tiled over directly on top. But the plywood has since pulled up at the seam here. I can press on the corner and it moves a bit, but it feels like there's a joist underneath. The tile have all gotten loose or broken their grout in this area.

Should I try to remove the popped up tiles and then screw it down to the joists below? Then I was thinking of cleaning out the old grout and tile backs with an oscillating tool and then putting the tile back down. I've never tiled anything so not sure what to use to set it and for grout, but I'm sure I could look up a video somewhere :)

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  • Are the joists still structurally sound?
    – JD74
    Apr 29, 2023 at 14:22
  • What condition are the joists under that floor? Any rot in the joists? How thick is that plywood? Tile requires very solid floors and usually a good inch of sub floor(plywood) is recommended.
    – crip659
    Apr 29, 2023 at 14:22
  • Would guess the plywood is too thin, and the desire to avoid a thicker floor and a step up kept it from being thicker and having a layer of cementboard on top. Ideally you lower the joists and build a thicker floor, but that's hard/expensive as a retrofit .vs. at design/build time.
    – Ecnerwal
    Apr 29, 2023 at 15:18
  • @JD74 yes I've been under there and had it inspected too. I measured the top sheet of plywood to be 0.825" but there might be a second sheet underneath. One thing I noticed was they used screws everywhere else but a nail in the corner.
    – confused
    Apr 29, 2023 at 17:23
  • Can you measure the thickness of the plywood? How far can you stick something down in that gap (once you've cleaned out all the grit)?
    – Huesmann
    May 2, 2023 at 13:47

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Tiles popping are relatively common. Floors aren't always at TCNA specs - 1 1/4" thick plywood. For a bathroom your spans are likely small though. For the amount of work to fix this correctly, I'd give epoxy grout a try.

Homerenovision on youtube has some good epoxy grout videos where he fixes popped tiles as the epoxy grout actually adds structure to the floor and helps tiles with deflection.

You shouldn't have movement/deflection in your subfloor and you'll want to make that as solid as possible. If you can get under the floor and add blocking to the joists to make this area more rigid that will also help.

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