Just to add some more facts about this wall.
It is a very exposed, and badly neglected wall. In some parts when I discovered that rain was getting in, I could poke my fingers through some of the holes. The pointing is in a terrible shape.
I have done some repointing to stop the rain entering, Yes, I used cement, and it has now stopped any rain penetrating through holes, but I dare say it is still oozing through the poor brickwork.
All the spalling is on the inside.
On the room side of the wall, the roof above is a sloping pitched roof (one way, sloping down from the wall above the room, to the wall on the other side of the room). it is in this void where the damage is. (The other wall is in excellent shape. It is just the other stretch of wall that is so bad) It seems that most of the houses here have problems with the wall on that side due to the elements bashing it. We have had several very rainy, windy days here and I have poked my head up there daily with a light and have seen no rain ingress at all, although it may still be oozing through the brickwork, but I saw no obvious sign of it.
There is absolutely NO insulation at all there at the moment, or has been in the past. There has been loads of air flow because the brickwork up there has been so bad.
The room below has been very, very cold during cold spells in Winter, even with the radiator working at max. I am assuming this is because of no insulation and the holes allowing the wind to penatrate.
Obviously, I want to stabalise the spalling, waterproof the outside and then insulate like hell, before replacing the part of the ceiling that has been removed.
Steve...