Bed thickness (600x400) 10 or 12mm? - Tile Advice

[CharlotteTiling]

For a level floor.
The tiles are 600x400x9.
Reading old posts it seems 12mm is technically the right answer but would 10mm be fine?

 

[WetSaw]

Do you mean tooth size of the trowel? It depends how flat your floor is.

 

[CharlotteTiling]

Do you mean tooth size of the trowel? It depends how flat your floor is.

Yes, the notch size of the trowel.
The floor seems pretty flat all over. The worst low spot I can find, in the kitchen, is 2-3mm. I haven't been able to check the hall yet but will when I lift the carpet, I expect it to be similar.

 

[GoneGuy]

12mm notch trowel and back butter the tile

 

[Just Rizzle]

my rule of thumb is a mill less than tile thickness on flat floor and ALWAYS BACK BUTTER. this should allow tile to bed in and restrict the adhesive coming through the grout joint and give a little shuffle when in place to futher adhere the tile

 

[Spare Tool]

Yes, the notch size of the trowel.
The floor seems pretty flat all over. The worst low spot I can find, in the kitchen, is 2-3mm. I haven't been able to check the hall yet but will when I lift the carpet, I expect it to be similar.

How've you measured it to 2 or 3mm?

 

[CharlotteTiling]

How've you measured it to 2 or 3mm?

I used a 4ft level and a tyre tread gauge. I'm sure that's not the most accurate method, but the best I could manage with what I have on hand.

 

[acaciaguy]

12mm notch trowel and back butter the tile

This