Simple thing in Austria. Any circuit up to 32A has to be RCD protected. If there are major changes to old wiring it has to be upgraded, usually by fitting a single RCD.
Newer or recently rewired single-family houses often have a subpanel on each floor with individual RCDs. German Electricians recommend at least 2, rather 4 RCDs (2 for lights, 2 for sockets or at least 1 each). i think that's a bit over the top if you live right in the middle of the city where the street lighting shines into your windows 24/7. Otherwise it moght be a good idea.
