Advice on trowel notch size for bathroom floor mosaics please

16 Jul 2008
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Would appreciate a bit of sense check on the advice I've been given by the tile shop on trowel sizes.

I'm doing a bathroom where the floor will be mostly 60x60cm tiles but with a 5x5cm mosaic version of the same tile in the shower area. This shower area I have also sunk down 12.5mm when casting the floor. Walls are 25x50cm mostly with a 5x5cm marmor mosaic for the shower corner.

I was advised to use 8mm notch for walls, 10mm for the floor tiles and 4mm for the mosaics. This does seem in line with general advice I googled and I think I generally understand the reason for smaller trowel size for the mosaics (and it might help me on the walls as the marmor mosaics are thicker than the regular wall tiles).

But I'm wondering if it is right to use such a small size on the shower floor mosaics? Doesn't seem in line with general advice to ensure the floor tiles have a good full coverage bed. Also how on earth would I get the same overall thickness on the shower and rest of the floor with different adhesive amount? I know that isn't totally critical for me since I do have that step down for the shower area, but I'd still like the thicknesses to be the same ideally so I end up with my planned 12.5mm step and not significantly more, so it looks neat and works out with the 12.5mm round edge trim I planned to use round the step.

My gut is saying use a bigger notch size on the shower floor mosaics.

Any advicce much appreciated. Thanks!
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4mm notch is good for the mosaics. Too thick a bed and the adhesive will ooze out of your grout gaps. Once laid press them home with a grout float.
Thanks for the reply!

In the end I'd already gone ahead and followed my gut (which has tiling experience of one other bathroom ever, lol) and used the 8mm. I thought I wanted a good thick bed and it would help take out any unevenness on my manually shaped fall to the drain in the sunken shower area. I'd used the 4mm on the wall mosaics and seemed that might be a little small for the floors. Did get a little oozing through in a few places, but was OK. I think a 6mm might have been better (did see Americans generally using 1/4" on youtube vids :)) but didnt have one.


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