Is there a consequence to using too large a notch trowel, aside from wasted thinset? Asking for 2 reasons:

  1. I'm installing 16x24 tiles on a floor, with 5x5 "accent strip." Both tiles ~10mm thick. But if I use standard trowel sizes (1/2" for big boys, 1/4" for small), the thinset-thickness-difference could cause lippage. So is it okay to use the 1/2" for both tiles? High traffic area in a shared bath, plenty of point loading on those 5x5s.

  2. I'm tiling a shower with Kerdi Board. Before I installed the Band, my walls were dead plumb & flat -- but not now, thanks to buildup at overlaps (e.g. around niches). IMHO, I installed it perfectly, using All-Set, with no excess thinset. There is clearly lippage if I dry fit a few 6x12 wall tiles. I was gonna use a 1/4" notch here... what if I use a 1/4" x 3/8" notch instead? Or maybe a leveling system? In lieu of floating the whole thing... These are not the flattest 6x12s I've ever seen... Thanks!

  • 1
    I notice that you have many unresolved questions. Please take the tour so you know how to use this site well.
    – isherwood
    Nov 14, 2022 at 21:43
  • Got it, thanks isherwood!
    – borisj
    Nov 15, 2022 at 15:14

1 Answer 1


No one I've ever worked with changes trowel size mid-floor. Use the larger notch throughout. If you find that the smaller tiles are sinking in further, back butter them with the 1/4" trowel so there's more mortar under them. In all cases be sure that edges are well supported.

Regarding #2, use whichever trowel gets you good results. Tiling is an art, not a science. As long as every tile is well bonded and supported, it's fine.

  • 2
    Thanks for the perspective. I'm a framer, and have so many experiences of ending up terribly off on Step 25 because I was 1/16" off on Step 2... so I'm really paranoid with tiling.
    – borisj
    Nov 14, 2022 at 21:20
  • 2
    That's a good mindset. Preparation is crucial.
    – isherwood
    Nov 14, 2022 at 21:42

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