Help! Plaster coming off in sheets and crumbling.

[claptrapped]

I started stripping the wallpaper in of the lounge in our newly bought house (a 1930s semi). We noticed an area near the bay window where there were mould spores behind the paper and there may have been past damp because the outside wall seems to have been recently re-pointed (no damp was detected here during the survey). As I stripped further paper, the plaster began to crack and come off in sheets. There was crumbling plaster behind so it's making a big mess. It will obviously need to be sorted out by a professional, but in the meantime should I try and preserve the loose plaster in place or just get it all off? By taking lumps off I'm not sure if I'm creating a bigger job, or if it will have to come off anyway.

It will all have to come off to bare brick and any damp issues resolved before replastering.

did you use a steam stripper?

show us the outside of that wall please, including the gutters, windows and downpipes.

p.s.
the plaster looks to be creamy off-white. If it's that colour all through, it's probably lime plaster, which is fairly durable in damp conditions. It may have gone soft, though.

We have a similar problem, apparently steam from the stripper causes the plaster to blow. Ours isn’t too bad so we have been told to blue grit it ourselves then a plasterer is coming to reskim the walls. I would get advice from a plasterer before you carry on.

That doesn't look like damage caused by a steam stripper to me. We have removed paper in our 1930s house also and while ours is pretty blown it is not as bad as that (we've managed to line on top without replastering) we don't have lime plaster however