If you take out he insulation the floor will probably not meet the minimum requirements for building regs. You could put in 25mm insulation and 35mm anhydrite screed but I suspect as with the sand cement and the topcem options it would prove expensive cmpared to a simple floating floor. Quintherm Polyurethane or Knauf XPS board would provide a rigid enough substrate and would probably be cheaper than Rocksilk. Overboard with ply and then decoupling membrane - jobs done cheap quick and easy.
It is unlikely to be a flat if it is just polystyrene under chip board unless it is on an insitu concrete slab which would be unusual for flats. Would normally be pre cast concrete planks and there would normally be a resillient layer and more usually nowadays a screed on top to give the acoustic performance.
It is unlikely to be a flat if it is just polystyrene under chip board unless it is on an insitu concrete slab which would be unusual for flats. Would normally be pre cast concrete planks and there would normally be a resillient layer and more usually nowadays a screed on top to give the acoustic performance.