Preparing old bathroom walls for large format tiles

[meanpeach]

I'm renovating an old Victorian property, as part of this I am refitting a new bathroom which will have wet room type shower in one corner and large format tiles on the walls approx 30x40cm. The present walls are finished with the original wet type plaster about 3/4 inch think, while not the flattest surface I've seen, they do seem to be adhering to the brick work pretty well.

What would be the best way to create a good base for these tiles, especially around the shower area. As far as I can see my options would be to skim the present walls then seal them with a tanking product - but would this give me a sufficently flat surface and be resiliant enough for the shower area.

Or should I go back to the brick, baton the walls and put up new aqua board. If I do this, do I still need to get the walls skimmed or can I get a tiler to put the tiles directly onto the aqua board??

Any info or advice would be greatly appreciated.

 

[keyplayer]

Here's a method I've gone for more than once in the past, with success:

Overboard the walls with 12.5 mm WBP. Probably plug and screw if the walls are good. Seal the board with dilute pva, 4 to 1 ish, this will prevent any bleed through to the grout from the board. Then tile. Take care to eliminate any movement between adjoining boards in the corner.