[myriadoptimum]

Depending on where you are in France (especially places with lots of housing stock being older buildings), it's common (if not the norm) for there to be no unit numbers and to direct people to apartments by floor number / door position relative to stairwell.

[wongarsu]

That doesn't surprise me, same thing in Germany. However having multiple buildings with the same house number (without distinguishing letters) sounds like the much worse oversight here

[taejo]

Though at least in Berlin it's pretty common for multi-family houses to have a separate wing (Seitenflügel) or rear house (Hinterhaus) that are reached by entering the street door of the front house (Vorderhaus) and then exiting through a door behind the staircase into a courtyard before entering the second building, and at least in some cases each building has its own set of mailboxes, all with the same address.

I regularly have the problem that deliverers don't read my delivery note and don't listen to what I say on the intercom, and go all the way to the top of the front house before realising I'm in a different building altogether.

[postepowanieadm]

That may be because Code Civile allowing(used to allow)((par 664?)) ownership of floors.