Gutted bathoom. How best to prep for tiling

[WordBear]

I've gone cross-eyed reading threads on here trying to work out how to get my bathroom ready to be fully tiled with 600 x 300 x 12 marble tiles.

The bathroom has been completely gutted. The walls are back to bare brick and there is no floor just (new) floor joists. It isn't going to be a wet room.

For the walls, I thought from reading on here that it was best to get them sand and cement rendered - no skim. Every plasterer I've had in to quote has been surprised by that and has said to dry-line with plasterboard instead. One even checked with a tiler while I was there and he said it would be more likely to crack. Should I dry-line it or render it? I don't mind waiting for render to dry if it is better. Everyone I mention the render to has never heard of tiling like that.

Secondly, if there is no floor and it is just wooden joists am I right in understanding it is best to use the 22mm tile backer board? Is that more expensive than using 18mm ply with 6mm tile backer overlay? If the 18mm ply with overlay is better, what kind of ply is that supposed to be? I priced it with marine ply and the cost seems similar to using 22mm tile backer board.

Cheers for any advice.

 

[Dumbo]

I would fix jackoboard to the walls , dot and dab on tile adhesive with mechanical fixings through the board onto the blockwork and if it's the same price why not use the 22mm cement board for the floors as this is what it's meant for .

 

[WordBear]

Thanks I'm looking into jackoboard now. I hadn't even heard of that!