It's either cast in situ concrete (a lot more than an inch) or
prefabricated concrete floor beams (don't know if that was used in the
1970's) also a lot more than an inch. If so, any wooden ceiling joists
are only designed to hang plasterboard from - not chairs/people.


I would expect a 1970's flat to have decent fire protection between
flats/floors - more than plasterboard/joists/floorboards. Are you sure
there isn't concrete in there somewhere?

I think there is, going by our floor - some sort of bakelite type tile
over at least an inch of concrete - hence my original comment about
needing to check out the nature of the structure between levels.