the only time i have seen this type of plaster slab walls was on the twin operating theatre in Colchester garrison.
it was built with shadow gap detail, my job was to fill the gap in as it was not acceptable in a hospital.
the walls and ceilings where then sprayed with plasterpak a mixture of plaster and paint so that the whole room could take a high power hose down at the end of the op.
factory builds where becoming popular in the 60s using scandinavian methods.