WBP or cement board under floor tiles?

[SomeUser]

I have approx. 22mm thick floorboards over which I want to tile (I don't know the tile type or thickness yet as we haven't chosen them). Should I put the recommended 12mm WBP down, or (as I've read elsewhere) cement board? If the latter, what thickness should I use, 6mm or 12mm? Thanks.

 

[chris_o]

I would thoroughly screw the floorboards to the joists (being careful to avoid cables/pipes) then prime the floorboards with sbr.

Wait for this to dry then stick 6mm cement boards down with a flexible cement based adhesive. Screw the cement board down as you go (you can buy suitable screws for this, hardi screws for example). You probably want around 18 screws per board.

You also need to tape the joints of the boards, this can be done as you go as well. Use the correct tape (similar to scrim tape but made of a different material). Bed this tape down with tile tile adhesive and smooth off.

 

[SomeUser]

Thanks, Chris. You reckon 6mm will be rigid enough then?

 

[HERTS P&D]

Use 12mm, 6mm will flex.

Andy

 

[chris_o]

6mm cement board is what you use for overlay on floors, not 12mm. I’ve laid countless floors with the method explained above with no failures. Full bed of flexible tile adhesive with an 8mm notch trowel coupled with the correct type and number of screws will be absolutely fine

 

[HERTS P&D]

All the pros that I work with only use 12mm.

Andy

 

[chris_o]

All the pros that I work with only use 12mm.

Andy

You really are chatting rubbish mate, and now filling someone with doubt where it is not needed. As above, 6mm is used as an overlay on a throughly fixed timber floor with little to no deflection. With a full bed of adhesive underneath, the ‘flex’ issue as you put it doesn’t even step in to the equation. 12mm can be used on the floor, but has no effect on rigidity, only to make up heights if needed, but usually you would be after the least build up possible.

@SomeUser Have a read on the james hardie website about Hardie backer. They will tell you all the info you need to know, including that you use 6mm for floor overlay.

 

[HERTS P&D]

12mm can be used on the floor,

Thank you for agreeing with me.

Andy

 

[chris_o]

Thank you for agreeing with me.

Andy

No problem. But on a serious note, stop giving people completely the wrong information. You obviously have zero clue what you’re talking about, and you’ve just highlighted that again in your last comment. I’d also love to see these ‘pros’ you work with, they obviously have zero clue either. Stick to your drainage pal...

 

[HERTS P&D]

 

[HERTS P&D]

Stick to your drainage pal...

Its called 'the brown gold'

Good luck with your tiling, hope your knees are ok.

Andy

 

[chris_o]

Abuse of member's family removed