Sub-floor for bathroom , Travertine tiles

[Renter27]

Got Travertine tiles for the upstairs bathroom , its just pine floorboards at the moment - wondering if a 6mm plywood is sufficient for the sub floor ? Or would 9mm be better ? When screwing it down does it need to be screwed into joists or just the pine floorboards ? Cheers

 

[galwaytt]

Do not use plywood, full stop. It will eventually expand/contract, and you're tiles will move with it. Plywood is a natural material, and behaves as such, and this is something you don't want, behind tiles.

Use something like Tegral Hydropanel board, Versapanel, or Hardibacker 500. These are NOT wood-based boards, are impervious to water, and are temperature stable.

I used Hardibacker 500 in 6mm in my bathrooms - including walls - sheets are small too, so easier to handle. Insulation Distributors in Dublin are the importers iirc, but I think Chadwick's stock it.