Seeking Advice neighbour cut our electrical wires

Hello everyone,

Facing a stressful situation in Marseille, South of France - our upstairs owner cut our electrical wires during their renovation, leaving us with no lights and a damaged ceiling. The wiring runs from our ceiling, through the concrete part of our shared floor/ceiling, and into their so-called 'couscous' space.

Key Points:

• Upstairs owner claims it's in their private space, so no responsibility. They argue that the wire they cut was sticking above the shared concrete part and in their private area, asserting they have the right to cut it since our electric wire should have never gone through their private floor part.
• We've lost rental income due to this issue.
• House insurance won't cover loss of rent; seeking legal cover.
• Building management and syndicate not very helpful.

Response from Building Management/Syndicate:

• Private and common elements are governed by the co-ownership regulations.
• According to them, our ceiling is private, the concrete slab is common, and their "couscous" space is private.
• No common conduits, each apartment has its own.
• Upstairs owners are lawyers, adopting a high-handed approach, have been rude and dismissive.

Questions:

• Is the upstairs owner responsible for checking and consulting before cutting the wires that pass through our shared space?
• Any advice on legal recourse for loss of rent and negligence?
• We're in a tough spot, and any helpful insights or similar experiences would be greatly appreciated.

Thank you!