James Amor wrote:
"John Rumm" wrote:
Have you thought of simply rendering the wall using a sand cement mortar
with some waterproof admixture in it, and then tiling straight onto that?

I had thought about it, but I'd like to keep the amount of time the bathroom
is out of use to a minimum and I don't really want to have to wait for
render to dry.

It would only take a week, and tiling onto render as JR suggests
is far better than tiling onto gypsum plaster for this situation.


Also, I'm not sure if I could manage to get it flat enough to
tile!

Easy peasy, do it in sections if you really need to, or get a
plasterer to do it (after you've done the prep.).