Never fill this gap with grout because tile grout is not flexible.
Gap between wall tile and ceiling.
The tile council of north america recommends at least a quarter inch gap between the tile floor and the walls.
Caulking is the best choice for this application.
In all cases covering the seams between.
Alan the floor of your shower looks great but it agree that there seems to be too much of a gap between the wall tiles.
You can then proceed with normal joint taping techniques using drywall joint compound which drywall professionals refer to as mud.
Photos attached hopefully i think they re upside down but what you re looking at is the corner where the tiling is on one wall and that wall meets a plastered wall and a plastered ceiling.
Maybe it will look better once it s grouted but right now my eye focuses on the gaps and not the beautiful stone.
We had to replace the drywall ceiling above the shower which was buckling and wavey.
Instead fill it with an elastic material capable of sustaining the movement of the floor and the movement of the wall.
Although the covering on most ceilings is drywall that isn t the only material that builders use.
The tile is level the ceiling is not.
The only place that the gap gets any larger is on the one outside wall.
Acoustic tiles and composite panel boards are two others.
When i put the inside the shower last tile on there was only 1 16 to 1 8th inch gap.
All it takes is a quick patching job with fiberglass mesh tape.
So now there is a varying gap 0 to 1 4 between the top of the tiled wall and the ceiling.
When the ceiling changes height across the length of a wall a gap between wall and ceiling can result.