It's a 100m2 apartment, not a house. Heating and hot water is natural gas. Anything else would require a much bigger feed. For example, an electric heating system for an apartment of this size, installed in the 1950ies or 60ies already had 35A 3ph, dedicated service just for the heating. The 6mm2 single phase are just for lights and general purpose Schuko receptacles, plus washing machine and dishwasher (draw less than 3500W each and are wired on dedicated 16A circuits).
Today the electrician came by to inspect our work, he just took a short look and went away to send in the completion note. Saved us nearly 2000 Euro doing the work ourselves. However, I hope I'll never have to work with 6mm2 solid again. That stuff is a bit too solid for me. Bending it around the terminal screws was a pain.
