Not filling the gap can allow water to migrate undeneath the tiles.
Gap between floor and wall tiles.
As the tiles increase in size a larger gap becomes acceptable.
Gently spread the tiles and place two spacers between them one at the top edge of the seam and one at the bottom edge.
For smaller tiles is advisable to use small spacers.
I m guessing its the thickness of the dot and dab then plaster board then tile adhesive then tile.
These can be left in place and will not be seen when you have completed your tiling.
Never fill this gap with grout because tile grout is not flexible.
If you have tile on the wall adjoining the tub select a caulk that matches the color of the grout.
To read the rest of the thread look here.
The d i y video how to seal a big gap between tile floor and tile wall in a bathroom or shower.
There is a gap of say 5mm to 8mm give or take high between where the floor tiles meet the wall tiles in the bathroom.
Fill gaps larger than 1 8 inch.
If your gap is smaller than 1 8 inch in width use regular caulk.
Gently push the tiles together so the spacers are tight in the joint.
It shows how to seal a gap in the corner where the tile floor.
The gap goes 3 5cm to 4cm back to the breeze block.
Caulking is the best choice for this application.
Place them between the tiles are you lay each one and grout straight over the top.
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.