Tiling onto backing plaster, skim coat, or strip back and board? - Tile Advice

[OllieM]

Hi all, first post here - total novice in need of advice.
I’m retiling a shower room and removing the old tiles has taken the smooth plaster surface with them leaving what I assume is backing plaster. This is sound and level other than a few gouges. This wall is the opposite end to the shower so not directly in contact with water but am planning to tank it to be safe.
Question is can I tile onto this plaster or do I need to either remove it and cement board or skim coat first? If I need to skim, how long does this need to dry before I can tile it?
Attached are pictures of the wall in question, the top half will be tiled, the bottom half will be built out into a ledge box section and that tiled. Cheers.

 

[Perfect Tiling]

Hi Ollie.....if the tiles are within the limit for plaster (20kg/sq mtr) then you will be ok to tile over. I would use a tanking kit that has a supplied primer as some tanking won't stick to plaster.....it just peels off like a skin. Mapie do a tanking kit with a primer....water it down so it soaks into the plaster rather than sits on it

 

[Dave]

If its backing coat then i would prime and burn/float coat the surface with adhesive to create a key. Bonding coat is fragile/soft so won’t hold your tiles if you don’t get a stable topcoat.

 

[OllieM]

Thanks for all the advice, appreciate it. Tiles are fairly lightweight 25x20cm ceramics but maybe it’s better still start from scratch and know where I am.