Bathroom floor advice needed...

[AskyourmA]

Hi all, new member and my first post...
I’m doing a full bathroom refurb. I last did it about 12yrs ago and that job lasted with no leaks or lifting or cracked tiles etc. But from some up to date research, previous job was all wrong. 6mm plywood screwed down on t&g floor boards, sealed with pva then tiled over with tubbed unibond wooden floor stuff. But as said that job has lasted 12yrs.
Change of decor has forced this refurb...
Anyway back to the job. I’ve screwed down 12mm WBP, I ordered external WBP, but to my horror and only noticed when plywood was fitted and screwed, they delivered internal grade stuff. The floor is now very solid with no creaks or movement and I have 6mm backer boards to fit over the plywood.
Can I stick with the plywood that’s now fitted?
How do I fit the backer board? Is 25mm turbo gold scews enough without using adhesive. My fear with adhesive on the plywood is that it is not external grade stuff.
If adhesive is 100% needed as a thin set between plywood and backer board, do I need to seal/prime the plywood.
What tape do I use on the backer board joints?

Thanks...

 

[Lou]

Welcome to the forum, glad you found us 🙂 Have you got any photos of your project so far?

 

[jdnest]

Hi all, new member and my first post...
I’m doing a full bathroom refurb. I last did it about 12yrs ago and that job lasted with no leaks or lifting or cracked tiles etc. But from some up to date research, previous job was all wrong. 6mm plywood screwed down on t&g floor boards, sealed with pva then tiled over with tubbed unibond wooden floor stuff. But as said that job has lasted 12yrs.
Change of decor has forced this refurb...
Anyway back to the job. I’ve screwed down 12mm WBP, I ordered external WBP, but to my horror and only noticed when plywood was fitted and screwed, they delivered internal grade stuff. The floor is now very solid with no creaks or movement and I have 6mm backer boards to fit over the plywood.
Can I stick with the plywood that’s now fitted?
How do I fit the backer board? Is 25mm turbo gold scews enough without using adhesive. My fear with adhesive on the plywood is that it is not external grade stuff.
If adhesive is 100% needed as a thin set between plywood and backer board, do I need to seal/prime the plywood.
What tape do I use on the backer board joints?

Thanks...

Hi

I'd say you'd be ok with normal ply, but I would SBR prime it all over before fitting, especially the edges. You can use some thing like Ultra Tile Pro Primer or even external grade wood glue slightly watered down to seal the ply.

You can use normal screws, making sure they're countersunk, or Hardiebacker do specific screws for that purpose that are also adhesive resistant. I would definitely use S1 adhesive between the ply and Backerboard and screwed down spacing as per their instructions.

I always give the backer a coating of primer too, just belt and braces really.

Hardie make a tape specific for joins so put that down with thinset too, or another mesh tape will be fine I'm sure.

Depending on what you're doing, you could use an uncoupling membrane too, but no need if its under a shower tray/bath...

Hope that helps...

 

[Anthony]

Why not just use 12mm cement board? Get rid of the ply all together screw down every 150mm/200mm use an s1 adhesive (ultra’s my choice) job done. The less timber involved. The better in my book!