Cement board on plaster

[Bleeping_thing]

I'm redoing my bathroom soon and was wondering if you could put cement board over plaster?
For reference, it's a 1950s brick house, the brick has been plastered over in the bathroom but want to tile floor to ceiling.
Would I be able to dot and dab and then screw the board to the wall to then tile over or is it best to remove plaster from the wall and put the cement board directly on the brick?
Or maybe I could do away with cement board altogether and just tile straight on the plaster with the right prep?
I have heard lots of contradictory info online about this.

 

[martygturner]

In any tile backer board you need to use some mechanical fixings, screw, washer and plugs as well as dab. I would check the walls for level and squareness, you can true up the walls pretty easily with tile backer, leaving tiles square rather than at a slope makes the finish much nicer., sealing the joins adds a lot to the water tightness of the job. You can use it over plaster but then again you can tile straight on to plaster. The prep of plaster is important get a straight edge over it and fill in any lumps and sand out bumps...otherwise the tiles will lip, ie show the edge.

Prep the wall with some plaster tile prep loads out there, but remember that gypsum plaster has an adhesion limit of 20kg per m2 thats for tile adhesive and tiles. so that may limit your choices of tile.

If you are going for a wet room then tile backer every day.