ᐅ Flatness Tolerances for Tiles

Created on: 13 May 2024 08:54
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bruno1990
Hello,

I am currently preparing the surfaces for tiling in the bathroom. The walls have been skim-coated with Rotband (a finishing plaster), and the waterproofing with a sealing slurry will follow. The deviation over 1 meter is about 1-2 mm (0.04-0.08 inches). This means if I use a spirit level, a 2-cent coin (1.7 mm / 0.07 inches) either does not fit underneath or just barely does.

The floor has a deviation of about 1 mm (0.04 inches) over 1 meter.

Tiles of 60 x 60 cm (24 x 24 inches) (porcelain stoneware) with a thickness of 8 mm (0.3 inches) will be installed everywhere. The tiles will be laid using the buttering method (a notched trowel with 10 mm (0.4 inches) notches on the substrate and 4 mm (0.16 inches) notches on the back of the tiles).

Is further leveling or surface improvement necessary here, or is this sufficient?
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bruno1990
17 May 2024 20:18
So, the difference (including bulges) is about 4-7 mm (0.16-0.28 inches). I assume this can be evened out when laying the tiles. There will be a second layer of waterproof slurry, which might help reduce the difference slightly.