tiling on floor boards in bathroom

[Gamp]

Hi,
Just about ready to start preparing the floor for laying tiles down in my bathroom. I'd like to use ply as I don't have to put any adhesive or compound onto the floorboards which I am sure will damage them in some way. The only thing is that using ply am I right that I should be using 15-18mm? This, with a 8mm floor tile and adhesive, will mean close to an inch step up from the hall way carpet? The bathroom floor is small (1.4mx1.7m) and the boards are sound so will a thinner ply cause me issues?
Many Thanks!

 

[AdrianMealing]

You could use a 6mm cement backer board, providing there is no deflection in the floor and they are sound. Have a look for posts regarding Marmox, Aquapanel or Hardibacker.

 

[mypetearthling]

If you use ply, it will need to be screwed down at 6" centres to minimise movement, so the floorboards will take some damage anyway. If you really want to save them, you could lift them and then board the floor with 25mm ply (would need to give more details on your joists, once you can see them) Other than that I'm stumped, I'm afraid .


K

 

[Richard C]

The BS & adhesive manufacturers spec for ply over boarding is 15mm WBP but it’s generally accepted that 12mm is sufficient in most cases; or you could use 6mm tile backer boards as suggested. Either way the existing floorboards are going to be damaged from screws (fix every 150 through into the joists) & the additional adhesive necessary in the case of the thinner backer boards.

If you want to save the floorboards for posterity, pull them up & fix 18-25mm WBP ply directly onto the joists (my preferred method); the ply thickness you need will depend on the joist size/pitch/span. This will also keep your threshold down to manageable levels.