Just recently, I had occasion to try to look up the design standards for
floor loading for residential construction in the USA. There apparently
isn't a uniform standard here, as building codes vary widely, but quoted
figures for "live loads" (the load that is produced by use and occupancy,
as distinct from the load produced by elements of the building itself)
range from 30-50 lb/ft^2 of uniform loading (150-250 kg/m^2).