Cracked Bathroom Tiles on Plywood

[Ptolomy]

Hi, I hoping someone here can help as you seem to know what you're doing more than my builder!

We had a new bathroom installed a couple of months ago. The builder replaced one of the internal walls with a plywood wall. Now there is a crack running horizontally right down the length of the wall, and also some vertical cracking behind the radiator.

He is coming back to repair it but seems to think it's just because the wood has now dried out that it's cracked, and redoing it will be fine.

From a bit of googling it seems like this is a common problem with tiling onto plywood so I don't want the same thing to happen again.

What's the best solution please - does the whole wall need redoing or can some kind of more suitable board be put over the Plywood? There's not a great deal of spare space as there's only about a 1cm gap between the units and the wall.

Thanks

 

[Tim@Larsen]

Hi Ptolomy,

Cracks like this are usually as a result of movement of some type. You'll know better if you take the tiles off either side of the cracks. I'm guessing it is either shrinkage of the plywood from drying out or insufficient support behind the edges of the boards.

If lack of support is the issue you may get away with oversheeting the plywood with a 6mm cement tile backer board. Although again make sure the new board is securely fixed to the studs and not just the plywood and take advice from the board manufacturer.

Plywood walls are common in bathrooms with the perception that it is a better job than plasterboard in 'damp' conditions. Nobody doing it this way seems to appreciate that all timber expands and shrinks with changes in moisture.

 

[Stef]

I will bet you that the cracks are running where the ply is joined.
Builders love tiling onto ply, why??
Because they don't know any better & they think its waterproof.
He would have been better off using plasterboard & tanking it, as long as it could take the weight of the tiles.

 

[CJ]

Why O why has he used plywood? Would have been better & cheaper to use plasterboard.

 

[White Room]

How thick is the ply....