Permanent and useful loads precast concrete slab


Good evening! I bought a few months ago an apartment in a Russian building built in 1956. Under the solid wood parquet in the bedroom and living room I found another layer of wood and a filling of earth, rubble. Thus, we reached the slabs of the block, and the difference in height between the rooms and the hall (where there is a screed covered with mosaic) reached 15 cm. My question is does anyone have any idea what permanent useful load a precast concrete slab has. I know not all tiles are the same, but seeing how much weight they hold in mosaic spaces, I wonder if the same load can exist in rooms where that solid wood parquet infill used to be. Thanks!