We just moved into a terraced house that used to have a leaking roof. The roof was repaired two years ago and there is no longer a leak, but the evidence of it still remained in the top corner of our upstairs room where the wallpaper and plaster had been crumbling away.
We have now stripped the wallpaper and the crumbling plasterwork has naturally fallen away. However, we are now faced with a fairly large section at the top which appears to be grey concrete. Whilst it is not falling away, it is an area powdery to the touch and probably wouldn't take much for it to come away. Our problem is we're not sure what to do next. Should we knock the concrete away and reapply new concrete? Is this something we can do ourselves, or should we just leave the whole thing alone and let the professionals deal with it?
We've also noticed halfway down the wall a diagonal pipe is starting to rust through the plasterwork - is this an old method of relieving the damp. Is it something we should aim to remove, or keep in?