Old plaster fell off wall

[marlb7204]

Hi
Decorating a bedroom and when removing 30 year old wood chip wallpaper, the plaster fell off with it in places. It’s only a small area about 5 feet by 1 foot. It’s hard to describe but that part of the wall is only 5 foot tall. It looks like it was done at a different time from the rest of the room. The rest of the paper is off and the rest is fine. Where it didn’t fall off immediately it cracked and felt like there was space between the plaster and the wall. It looks to me like it never stuck to the wall properly. It was maybe just finishing plaster straight on to concrete. The concrete below is rough and uneven. I’ve not done any plastering before but I think I probably need bonding plaster? I’m wallpapering the area after that. Do I need anything other than the bonding plaster? I think it’s probably going to be a very rough finish but I’m reluctant to buy another 25kg pack of finishing plaster that will never get used before it expires. Can I skim it with polycell plaster repair on top of the bonding plaster just to make it a bit smoother? That’s instead of the finishing plaster. It’s in a very hidden corner of the room, I’m not too bothered about how it looks.

 

[bobasd]

first thing is to strip all the room of wallpaper back to plaster (ceiling too?).
is what we are looking at a chimney breast?

then any loose or blown plaster should be hacked off back to brick.
any dampness revealed then come back here.
a bag of gypsum and a bag of finish shouldn't set you back more than say £15.