I've layed 3.5mm plywood instead of 12mm. How can I rectify this?

[RichTraff]

So I'm fitting a bathroom myself. All the plumbing, fixtures and fittinga are all straight forward to me. Tiling on the other hand is new to me.

I thought the floorboards were a bit rough so I went out and bought some 3.5mm ply and covered it. I screwed it in plenty (every 6") and stupidily assumed this would be ok. It certainly doesn't feel like there's any movement.

I've fitted the bath, cupboards and toilet but done no tiling.

My plumber friend then pointed out that 12.5mm ply is standard to tile over.

I thought he was exaggerated but judging by the posts on here: I've done a 'cowboy' thing.

Question is: how do I rectify this? I can't take off all the units and start again.... or at least I REALLY don't want to. It'd take days to redo.

Could i just apply more screws? Ply over 9mm on top of the 3.5mm in the areas that the floor tiles are going on? Or should I rip up the 3.5mm where possible and replace with 12.5mm?

Other ideas welcome. Please don't slate me too much! I know I've cocked up! I nornally research things to death and the one time I don't...this happens!

 

[nickjb]

What you have done is fine for vinyl flooring or vinyl tiles. I'd fit that, much better that ceramic tiles on the floor IMO.

 

[RichTraff]

Interesting option, vinyl.

I was planning on standard floor/wall tiles which I assume are ceramic.

You may have gathered: tiling is totally new to me. People told me I could easily do it but I heavy underestimated floor preparation.

 

[r1flyguy]

Could you not put a tile backer board down over the top to build up the difference?

 

[mcluma]

Could you not put a tile backer board down over the top to build up the difference?

Get a proper cement backer board 6mm and you will be fine, best to put the board down with tile adhesive and than screw

and ...... stacker the joints.

 

[Happyplumber]

That is proper lash up sorry

Even 12.5mm ply is not suitable , we have ditra matting "No More Ply " Hardibacker Aqua panel and whole.myriad of other boards to use and all of these would do a proper job and not cause you headache afterwards
Rip up.and do it properly

 

[Paul C.]

The ply has to be a MINIMUM 15mm WBP overlay. To brace the floor from bounce you could also use 12mm Hardibacker, 10mm Marmox Multi Board.

Ditra matting will not take the flex out of the floor. It is a de-coupling membrane to prevent cracks from lateral movement, not vertical. So not necessary if overlay is used, unless you are in a new-build and the house still needs time to settle, or if the main substrate is newly laid.