Dunno about Spain, but in France, a relative in a ?9 story building basically gutted their place. Unlike North American condos, in France they own their window

Dunno about Spain, but in France, a relative in a ?9 story building basically gutted their place. Unlike North American condos, in France they own their windows and can replace them. They also built out a “frame” to install noise insulation on top of the shared walls, losing a bit of interior space (and a huge free bonus to the neighbours). Can’t remember if they did the ceiling too. Unfortunately, no flooring standards are an issue. In my Canadian condo, if you redo the floors, there’s some noise insulating requirement for your choice of flooring as it’s against concrete.