Another question about tiling on plywood.

[Ascot]

Hello.....hoping some of you can offer some advice.

I am in the process of tiling my bathroom. I have installed the shower tray in the corner of the room (brick/plaster walls) and built a fin wall on the third side. I have, however, used 18mm plywood to sheet out the fin wall. I realise now that i should have used a tile backer but now that its done, i can't get the ply off because its built right up to the shower tray.

I am using 250x380mm marazzi minimal tiles and Mapei Keraflex S1 adhesive.

I spoke to the technical guy at Mapei to see if i needed to prime the ply first and he said that it would not need primed but needs to be WBP at least. I'm not sure that it is, its just from B&Q. He said if it is not WBP or marine grade then it would need replaced (or sheeted over which i can't do because it would ruin my tile layout for the front face of the fin wall).

What would you do in this situation? If it's not WBP would priming it help? (He wouldn't comment on that). Or do you think this is totally necessary to take it all apart again? Is there any other treatment that might work? Or do i just tile away and hope for the best?!!

(I have already tiled the back wall of the enclosure.)

Obviously I dont want the tiles to fall off, but rebuilding the fin wall and box that is attached to the other side is A LOT of work to undo!

Hope some one can advise.

 

[widler]

can you not board out with 6mm,hardibacker ? its only 6mm,not a lot

 

[EverDon Tiling]

cant it just be tanked?

 

[widler]

cant it just be tanked?

if its rubbish ply can't the ply still de laminate even though its tanked ?

 

[White Room]

Theres a chance that if you tile directly to the ply some of the resins can seep out and discolour the grout as well....

 

[Ascot]

Thanks for the replies.

Widler - Sheeting over it with 6mm backer would be a good fix but i really don't want to because it would change the dimensions of the front of the fin wall which was carefully planned to take some feature tiles.

Whitebeam - that sounds even more worrying! Do you know if there is any such thing as a sealant that would prevent this or is that a no no with tiling?

 

[gamma38]

WBP Water and boil proof. Cheaper plywoods or lower grades tend to de-laminate easily, especially when adhesives are in contact with them. As whitebeam says also the staining can be a real problem. You need to find out what you have on the wall. It should say on your receipt.

 

[On one]

Theres a chance that if you tile directly to the ply some of the resins can seep out and discolour the grout as well....

Seen it happen!

 

[On one]

Even if it is WBP plywood,coming from B&Q what's the chances of it being quality WBP!

 

[Ascot]

This whole topic seems to be a mine field!!!! I have just read the product information for Keraflex Maxi S1 on the Mapei website and it says not to use it on wood. But the technical guy told me on the phone that i could. Too much conflicting information for me to have a clue how to proceed!