When tiling walls, it's customary to adhere to the industry standard of using 2mm tile spacers for achieving consistent and professional-looking results.
Tiles undergo contraction and expansion even after being installed. Without spacing, tiles would exert pressure against each other, leading to cracks and loosening. Tile spacers ensure uniform gaps and lend a polished appearance to the completed setup. While the choice of spacer width is subjective, historically 2mm was preferred for walls and 3mm for floors.