Tiling onto P5 Tongue and Groove Chipboard Floor Panel

[Duncan Warrender]

I have recently started refurbishing my 2 bathrooms and have came to tiling part of my plan.

In bathroom 1 I have screwed any loose floorboards to the joists so that there is minimal movement, and then I have put 2 layers of 9mm Ply Hardwood down with staggered joints and a layer of Wood Glue inbetween them to give me a 18mm rise. I got this Ply for free so thats why I have used that. The floor appears to be absolutley solid with no movement. I have left a 2-4mm gap between joints as well. I am also going to use a flexi adhesive from Topps Tiles. I also have a flexi adhesive from Mapei as well incase i run out (just whatever was in stock at Screwfix at the time).

Now on bathroom 2, i have replaced the floor boards with P5 T&G Chipboard from B&Q (due to places being shut for COVID-19) I could only get it here:
https://www.diy.com/departments/p5-...-panel-l-2400mm-w-600mm-t-18mm/1696267_BQ.prd

Now, my question is, I dont have any 9mm Ply left, but i do have quite a few sheets of the P5 left, could I stagger the joints and fit another 18mm P5 down on top of the existing P5 and would that be solid enough for laying floor tiles down on?
https://www.diy.com/departments/p5-...-panel-l-2400mm-w-600mm-t-18mm/1696267_BQ.prd

 

[Duncan Warrender]

I should have mentioned that Bathroom 2 is only 1.3 x 0.8 wide and contains a cloakroom sink and toilet only.

 

[JaimieH]

For bathroom 1 it sounds like you've committed to tiling over the ply so you'll have to make sure your adhesive is suitable for tiling over wooden substrates and follow the instructions. It will then be a case of putting your trust in the quality of the plywood and hope you don't have any issues. With bathroom 2, although you have some 18mm chipboard left over, I would recommend overboarding instead with 6mm No More Ply. This has an equivalent strength is 15mm ply, it is not affected by moisture, will not rot and carries a lifetime guarantee if used correctly. Tiling on wooden substrates is not recommended anymore and will always carry a risk even if all products used are classed as being suitable for wood. Sorry, I know it's probably not what you wanted to hear. The good news is it sounds like your floors are completely solid and deflection free as movement in floors prior to tiling is a common cause of failure.

 

[Duncan Warrender]

Thanks for your reply Jaimie!
I have triple checked the adhesive and its good to use on Wooden substrates.
I have looked into No More Ply but the simple fact is I have no more money left. I got quoted circa £5K for the 2 bathrooms, and i only had £2k. I have spent it all on materials and I'm just about at the finishing line.
If I were to ever tile again (maybe getting our kitchen done next) I ould most certainly use No More Ply, or Hardie backerboard i think it's called?
You live and you learn! thanks again

 

[JaimieH]

No problem, good luck with it all.