Tiling on Tongue and Groove

[jonnymck]

I'm thinking of tiling large format porcelain tiles onto an already T & G clad wall in my bathroom. The guy at the tile warehouse seem to think it would be ok if it was securely battened (the battens are every 400mm) and covered with a coat of PVA. I'm going to use Stoneset SP Flexible Adhesive.
Should I rip out the T & G and plasterboard out the room instead? Some of the bathroom has WBP ply on battens which i presume would be fine to take the tiles with a coat of PVA.
Any thoughts, much appreciated.

 

[gcol]

I recommend you rip out the T&G and screw plasterboard up. Tile straight onto this without pva.

 

[big-all]

completly agree with gcol

all thats probably holding the the txg up is a little 1" pin at every batton

also you can have 2 or3mm expansion at the joins would flexible adhesive be up to that!!!!

it is also good at cupping as it moves

 

[Softus]

I recommend you rip out the T&G and screw 18mm WBP plywood up. Tile straight onto this without PVA.

Second farourite would be Aquapanel, with plasterboard coming a clear third.

 

[gcol]

In my experience, tile adhesive doesn't adhere as well to ply as it does to plasterboard. Also 18mm ply is far more expensive than plasterboard and more subject to failure due to atmospheric conditions.

 

[Softus]

I've never had an adhesion problem when using adhesive made for tiling onto wood.

Plywood had the advantage of being more rigid than plasterboard, can be more securely fixed to battens, and doesn't crumble when wet.

I don't know what you mean by atmospheric conditions, gcol.

 

[gcol]

I was refering to changes in moisture - humidity, which is a problem in bathrooms.
I agree plasterboard doesn't like water, but if the tiles and silicone are applied correctly then it's not normally an issue.

 

[Softus]

I don't understand why you don't use for plywood whatever means you use to prevent plasterboard from getting wet.

Edit - translation: Whatever the method you use to prevent plasterboard from being affected by damp (which for me is also correct grouting and sealing), I don't understand why that same method won't prevent plywood from being adversely affected by damp.

 

[gcol]

Ah I see.
I'm not talking about damp as in water from the shower. I'm talking about moisture in the air. Moisture that will act on the ply and cause expansion and contraction that will be of a different rate to that of the tiles. Plasterboard is more stable to these moisture variations.

 

[jonnymck]

Thanks for all your advice. I think I'm going to rip it out and plasterboard the whole lot. It seems to be the cheapest way forward. ; )

 

[joe-90]

If you remove the T&G and the battens there may be a solid wall to tile onto.

 

[Softus]

I'm talking about moisture in the air.

I don't buy that - how is this moisture laden air coming into contact with so much of the ply that it will cause expansion on a large scale?

 

[gcol]

Who mentioned anything about a large scale? "Plasterboard is more stable to these moisture variations."

 

[Softus]

Who mentioned anything about a large scale?

Apologies - I was being lazy with my wording.

I meant: ...on a large enough scale for that expansion to be a problem.

 

[gcol]

Bal seem to think it's a problem - they recommend sealing the back and edges of ply sheets before tiling. http://194.223.92.131/pdf/Technical Data Sheets/B & C Technical Data Sheets/Bal_White_Star.pdf
Obviously by your comments you don't do this.