I used to think a 12mm trowel was fine for everything

I was laying some big format tiles in a bathroom last month and the coverage was just off, kept getting hollow spots. My buddy Mike came by, took one look and said 'you're still using that 12mm? For these you need a 20mm, no question.' Switched to the bigger notch and the difference was instant, full bed every time. Anyone else have a go-to trowel size they swear by for specific jobs?

3 comments

3 Comments

singh.harper1mo ago

Yeah, the 12mm for everything is a trap I fell into too. The thing is, it's not just about tile size, it's about how flat the tile itself is. A lot of those big tiles have a slight curve or warp to them. If you don't use a deep enough notch to put down extra mud, you're just bridging the high spots and leaving air under the middle. That's your hollow sound right there. A 20mm gives you enough material to actually press the tile down into and get full contact.

nancy_wood1mo ago

Oh man, that hollow sound gives me nightmares. My cousin tried to save money on his kitchen floor and used a tiny trowel on these huge 24 inch tiles. We were over for dinner and you could hear it CRUNCH when you walked, like walking on a bunch of crackers. He had to rip the whole thing out six months later because they started cracking. That extra mortar is cheap insurance.

logan_gonzalez1mo ago

Exactly, @singh.harper, that extra mud is key. Learned that the hard way on my own bathroom floor.