If your gap is smaller than 1 8 inch in width use regular caulk.
Gap between floor and wall tiles.
For smaller tiles is advisable to use small spacers.
Gap between floor tiles and wall tiles.
Place them between the tiles are you lay each one and grout straight over the top.
The d i y video how to seal a big gap between tile floor and tile wall in a bathroom or shower.
Fill gaps larger than 1 8 inch.
Caulking is the best choice for this application.
As the tiles increase in size a larger gap becomes acceptable.
The large format 18 inch tiles should have inch space in between.
It might loosen them and might rot the floor.
The tile council of north america recommends at least a quarter inch gap between the tile floor and the walls.
Gently push the tiles together so the spacers are tight in the joint.
Never fill this gap with grout because tile grout is not flexible.
The gap goes 3 5cm to 4cm back to the breeze block.
I m guessing its the thickness of the dot and dab then plaster board then tile adhesive then tile.
Instead fill it with an elastic material capable of sustaining the movement of the floor and the movement of the wall.
If you have tile on the wall adjoining the tub select a caulk that matches the color of the grout.
It shows how to seal a gap in the corner where the tile floor.
To read the rest of the thread look here.
These can be left in place and will not be seen when you have completed your tiling.