This type of construction is more typical for commercial or appartement buildings, and makes my life complicated!
The brick fill was done from above on temporary planking.
After removal of the support, it got 2 layers of plaster, the 1st mixed with straw.
Removing all the brick fill is not feasible in the timeframe I've got:)
I first stabilised the problem area by pushing the falling bricks back in.
It was not possible to push them all the way in as they were beginning to snap.
However, the worst point went from 25mm to about 8mm, a defect that can be plastered out later.
During this I discovered that the concrete was both of high quality and filled with small pieces of metal, not really sure if they are old nails and shavings or purposely cut pieces of wire. This is something I've seen in German bunkers but ever for a house!
In any case, the concrete is too hard for my planned 5mm drill bit. The next size up is 8mm, and the first one of those burnt up in 5 holes before I managed to interpret the readings on the stud finder...
The shavings would make it give a maxe reading EVERYWHERE! A distance of 25mm sorts out the the main steels, but it's not perfect.
The rest of the ceiling is now stripped and ready for the remaining joists, OSB etc.