Tiling over wood

[anderino]

Hi,
I am about to tile over a wood 'shelf' that was made at the end on the bath, as it wasn't long enough to fill the space along the wall.

My question is: Do I need to treat the wood (PLY) with anything? PVA?

Its just normal 9mm PLY, not outdoor stuff.

Also, without taking wall tiles off or removing the bath, the 'shelf' cannot be removed or changed for something better.

Thanks

[ultimatehandyman]

Ply is not ideal as it expands and contracts quite a bit.

Marine ply or WBP ply should be used at the very least.

PVA should never be used as a tiling primer, unless the adhesive manufacturer recommends it.

I'd use some WBP ply and then tile straight onto it using some flexible adhesive.