Prepping walls for tiling

[ScotchGas]

So ripped the bathroom out on a recently bought flat & one of the walls i’ll be tiling has bonding over plasterboard.
Was going to skim coat it & tank it, as it’s the side wall to where the bath will be, then tile over however i’m a bit unsure as to whether the bonding + skim will weaken the plasterboards weight taking.

Will the plasterboard take the weight of the bonding, skim & tiles ok sticking to the 20kg m2 or best to start ripping everything back out and re-panelling, which I really can’t be arsed doing ?

 

[bobasd]

for me, wet walls should be backer board or render. no need to skim if background is flat and plum.
but if you just leave the bonding over p/b and tank it then that should be OKref the weight issue.
if theres any doubt or movement in the background then it all has to come off.

 

[L95]

Skim weakens the wall dramatically. Just tank the raw pb.

 

[opps]

https://www.tiles.org.uk/services/frequently-asked-questions/#16

The link above gives the weight bearing loads for different substrates, as L95 says, skimmed plasterboard has a lower rating than un-plastered boards.

However i have always suspected that the load bearing is based upon tiles being horizontal (ie upside down) rather than vertical. Can any one clarify?