What should I lay on joists before tiling?

[mmdowson]

Thanks to all who gave advice on my 1st thread yesterday.
Please bare with me as I am having a blond moment, and thats hard for someone with as little hair as I have.:lol:

As mentioned yesterday, I am renovating my bathroom and am planning to remove the current varnished t&g flooring and replace it with a more tile friendly alternative.

The new bathroom is going to have a wetroom showering area, this I am planning to cover with a Tuff2 pre-former type tray which will be laid straight onto the joists which then will be tiled. The joists are laid to 400mm centers.

Once I have removed the remaining t&g what woud you advise that I lay the tiles onto?

I was thinking of either 18mm ply and then 6mm type backerboard or a thicker ply say 22-25mm and then a decoupling type matting.

Am I thinking correctly or amI barking up the wrong tree?

 

[Scott]

18mm should be ok on 400 centred joist but only you can see how much deflection there is. You may as well add more noggins while you are there. Teh cement board on top sounds good too