It might loosen them and might rot the floor.
Gap between wall and floor tiles.
To read the rest of the thread look here.
Current trends are moving towards leaving much smaller grout lines between tiles.
It shows how to seal a gap in the corner where the tile floor.
Caulking is the best choice for this application.
Never fill this gap with grout because tile grout is not flexible.
As the tiles increase in size a larger gap becomes acceptable.
For smaller tiles is advisable to use small spacers.
The tile council of north america recommends at least a quarter inch gap between the tile floor and the walls.
Ceramic tiles are available in a variety of sizes.
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 large format 18 inch tiles should have inch space in between.
The overall finish of your job really does depend on your own personal style.