Instead fill it with an elastic material capable of sustaining the movement of the floor and the movement of the wall.
Gap between wall tile and ceiling.
Caulking is the best choice for this application.
There is a slight gap between the tiles on the wall and the ceiling.
All it takes is a quick patching job with fiberglass mesh tape.
Acoustic tiles and composite panel boards are two others.
The tile council of north america recommends at least a quarter inch gap between the tile floor and the walls.
When the ceiling changes height across the length of a wall a gap between wall and ceiling can result.
When i put the inside the shower last tile on there was only 1 16 to 1 8th inch gap.
Although the covering on most ceilings is drywall that isn t the only material that builders use.
Covering this gap isn t a difficult process.
You can then proceed with normal joint taping techniques using drywall joint compound which drywall professionals refer to as mud.
So now there is a varying gap 0 to 1 4 between the top of the tiled wall and the ceiling.
In all cases covering the seams between.
The tile is level the ceiling is not.
Never fill this gap with grout because tile grout is not flexible.
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.
We had to replace the drywall ceiling above the shower which was buckling and wavey.
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.