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!

 

[Muse2k8]

I know it would be a pain but I would rip it all out and start again. If you leave it as ply you face a real possibility of it failing and having to start again in a year or 2 anyway but by this time sealants will have set, plumbing will be in and tiles will be up. At least by taking it out and using suitable substrates you will be comfortable knowing it will last hope this helps.

 

[AliGage]

Establish what the ply is first.
It's not ideal, but as long as the framework was built well, and it's WBP i think you'll be ok to tank it and tile. It's just a stud wall to create the enclosure right? Is there any pipework running through it say for a shower? And did you insulate the cavitys?

 

[The D]

do the job right or you will regret it. The effort it will take to re do now is nothing compared to what you will have to do when it all goes wrong.

 

[Aston]

i dont want to upset anybody here but ply, whatever the format should now not be used in water sensitive areas.
its unstable, contracts and expands throughout the year more than any other type of board. joiners are notorious for using it because, well, they are joiners and they think its strong but that doesnt mean it correct.

i can understand people using it years ago when we didnt know what we know now, but its UNSTABLE so you run a much higher risk of future problems...why would you want to do that, when there are better and more suitable products out there? it doesnt make sense does it...

ps i hope i dont come across as patronising its just i dont want to see people lose money, my intentions are to help, not critisize

 

[The D]

or you Could do it the Swedish way and throw a load of insults at it see if that works :lol::lol::lol:

 

[Ascot]

Damn it! Obviously the majority of responses are not what i wanted to hear!

AliGage - yeah it's just a stud wall to make the 3rd side of the enclosure (about 800x2000mm to tile on both sides). No pipes or electrics in it but no insulation in the cavity either.

The back wall of the enclosure is already tiled so if i took off the ply on the side wall, i'd have have to cut through the jointing tape i used vertically in the corner and not replace it, but i gues that is not the end of the world.

I think it may be possible to get the ply off without disturbing anything else but if i use hardiebacker (12.5mm) i'd need to pack it out to match the 18mm ply that was on it. Otherwise it would leave a gap to the tray and throw off my tiling layout. That hardiebacker is a bugger to cut too! I think thats partly why i used ply in the first place!

As EverDon Tiling suggested, would tanking that one ply surface in the shower enclosure be an option?

 

[Ascot]

May be i could just replace the shower side with tile backer so it's safe with water?
Is there a tile backer thats easier to use than hardiebacker? I've used it before and it weighs a ton and is difficult to cut.

 

[The D]

Home - wedi - The system supplier for innovative products this is good for the job

 

[Ascot]

That looks like great stuff. Wish i had seen that website before i started this job! (I'm sure it's a bit more expensive though.)
Is it definately ok for attaching to timber studs? Mostly seems to describe it in terms of being attached to solid walls.

 

[The D]

[video=youtube;P6eXOZi9gHk]http://www.youtube.com/watch?v=P6eXOZi9gHk[/video]

 

[The D]

Ceramic Tile Distributors | CTD, Bathroom Tiles, Kitchen Tiles, Floor Tiles etc.
accessories

 

[DHTiling]

May be i could just replace the shower side with tile backer so it's safe with water?
Is there a tile backer thats easier to use than hardiebacker? I've used it before and it weighs a ton and is difficult to cut.

Click the PHG wetrooms link in my signature.. much better prices on Marmox boards..and easy to cut with a utility type knife.

 

[AliGage]

Guys,

I hate to go against the grain, but i have to ask. I'm all for using the correct products, i agree ply is not a great substrate and both deano and Ed are correct in their recommendations.
However, from what the op posted i've taken this to be a stud wall built out into the room to create an enclosure space. So, with no "outside" influences (i.e no outside walls, rooms to effect any tempreture etc) would the following not be sufficient?

As long as the studwork is built well and there are plenty of regular fixings to a rigid frame. Insulate the cavity in the wall. This will keep tempreture consistant within the cavity and prevent any warping of the ply. If you then tanked the face of the ply, better yet the wall all the way round. Would the tanking not only waterproof the wall, provide a means of a de-coupler but also insult the ply from any heat transfer from using the shower?

I completely agree the ply shouldn't of been used in the first place, but, if the op really didn't want to take it out or if it was too much hassle. Do you think what i'm suggesting would be sufficient?

 

[The D]

It may work it may not but removing and re doing now is a lot better than re doing the job after it is all finished. Just my opinion

 

[Ascot]

Ok everyone. I think you have me convinced. I've pretty much got my head round taking the face off all of the fin wall and box frames that i've built and replacing them with backer board. Probably hardiebacker as i can just get it from B&Q. The wedi board sounds handy but i haven't seen any here in Northern Ireland. I'm usually a belt-and-braces type in my DIY so i'd rather do the job properly.

The only thing not done properly then will be the jointing tape at the back vertical corner. As i said, the back wall is already tiled so i wont'be able to re-apply the tape when i replace the ply side wall. I will however use silcone in the corner joint between the tiles so hopefully this will allow for any movement.

Some day this job will be done!