How flush should shower tiles be?

Question

The large tile that has been installed do not share a common plane, so the flat faceplate hardware that spans the transition between tiles leaves a gap where water seems like it could potentially enter behind the foam "gasket" behind the faceplate that does not come in complete contact with the wall.

Further, the top of the tile lip leads directly to the hole in the wall where the valve stem protrudes.

My question is: How important is the flushness of the tile in a shower like this? Would something like this cause damage later down the road by allowing water into the wall and down to the ceiling of the floor below?

A possibly important consideration: a 4 year old shoots the hand held shower water all over this enclosure.

Answer 1

You've oriented your question around the tile, but that's not where your solution lies unless you intend to tear it off and reinstall*.

I would use a clear pure silicone caulk to fill that void. Don't use latex. Cut the nozzle tip as small as possible, press the caulk in well, and wipe off everything outside the gap. Don't leave a visible bead. It'll take the color of the tile and be virtually invisible. You might even mask the plumbing first to keep it clean.

On second look I don't really see a gasket. You might run the bead all the way around except for a small gap at the center bottom (left for drainage). Wipe nearly everything away, though.

_{* Questions of subjective quality (opinion) are off topic here, which is why I didn't answer in that vein. See the Help Center. It's common for tile to have some level variation. How much is allowed is up to your contract, which likely doesn't address that specifically. Therefore, any insurance claim you do manage to receive will likely be for caulking expenses. I suggest asking your installer nicely to do it, or DIY.}

Answer 2

As you've seen, it's difficult to get large format tile (which it looks like you have) to be flat—the larger it is, the more out-of-plane it's likely to get.

Odds are low that very much water could get behind that plate. Assuming it's for a faucet/showerhead handle or similar, you won't have water flowing directly against that wall—at best it'd be splashes. If you're really worried, get yourself some foam rubber (like adhesive weatherstripping) and stick some on in a semicircle behind the plate, on the top half of the circle.