Asking "what notch trowel for tiles" is like asking "what shoe for walking"-it depends on where you're going. Tiles come in all shapes, sizes, and weights, and each needs a trowel that matches. Let me simplify it with a few golden rules.
For tiny tiles (mosaics, 5x5cm), a 3mm or 4mm V-notched trowel is perfect. These little guys don't need much adhesive-too much would drown them. I used a 3mm trowel for my bathroom mosaic floor, and it worked like a charm-no oozing, no mess.
Small to medium tiles (10x10cm to 30x30cm) do well with 6mm notches. This is your "everyday" trowel, great for kitchen backsplashes, bathroom walls, and small floors. Think of it as the sneaker of trowels-versatile and reliable.
Large tiles (40x40cm to 60x60cm) need 8mm or 10mm notches. They're heavier, so they need a thicker adhesive bed to stay put. My brother used a 10mm trowel for his 60x60cm outdoor patio tiles, and they've survived rain, snow, and his kids' skateboards.
Heavier materials (stone, marble) often need one size up from their ceramic counterparts. A 30x30cm marble tile, for example, does better with an 8mm trowel instead of 6mm-its porous surface soaks up more adhesive.
And don't forget: Wall tiles usually need smaller notches than floor tiles. Gravity pulls downward, so thick adhesive on walls leads to sagging. Stick to 6mm max for most wall jobs, unless you're using giant tiles.
