Plasterboard in bathroom

[lostdiyer]

I’m renovating my bathroom and installing tile backer board on several walls where tiles were removed. These walls are in and around the shower.

There are two other adjoining walls with moisture resistant plasterboard. Should I remove the plasterboard from these walls as well, or can I leave it and tile over it?

If I were to keep MR plasterboard, would I need to sand down the paint before sticking tiles to them?

The tiles I’m using are large 1200 x 600 x 8mm.

 

[Wayners]

Tile backer is used if walls have tiles on that are exposed to water.
Saying that. One of my walls above bath/shower is just standard plasterboard stud wall and been fine for 18 years.

Re prep. Read application data sheet for tile adhesive.
Probably says make sure it's sound. Seal with correct tile sealer