Never fill this gap with grout because tile grout is not flexible.
Gap between wall and floor tiles.
It might loosen them and might rot the floor.
Installing ceramic tile is an economical way to update the look of floors and walls during a renovation.
Not filling the gap can allow water to migrate undeneath the tiles.
The d i y video how to seal a big gap between tile floor and tile wall in a bathroom or shower.
The tile council of north america recommends at least a quarter inch gap between the tile floor and the walls.
To read the rest of the thread look here.
It shows how to seal a gap in the corner where the tile floor.
The large format 18 inch tiles should have inch space in between.
Caulking is the best choice for this application.
For smaller tiles is advisable to use small spacers.
How to space between ceramic tiles.
Instead fill it with an elastic material capable of sustaining the movement of the floor and the movement of the wall.
The overall finish of your job really does depend on your own personal style.