Tiling on skim coat and plasterboard

[ladwey]

Hi -- I have a very quick question about substrates. I've got two backsplashes for tiling, one that's had a skim coat and one that's 9mm plasterboard mounted on battens (to even out a very uneven wall for installing the cabinets). The tiles are 8mm thick, so about 18kg / m2 without adhesive, according to one online table. I've got some leftover wedi board from the bathroom, and I'm assuming I should use that on the plasterboard. I can screw it to the battens and use the washers it came with. I'm not certain about the plaster -- should I also mount a backer board on that?

 

[Wayners]

If the skim coat is solid and well stuck it will be okay