Sell the property completely or partial sale with investment?

Can someone recommend a small stone that has top ratings for sound insulation [...] as a partition between apartments,

It should then of course also provide appropriate fire protection. In sound insulation, it is also important that the wall itself does not act as a transmitter. So a wall that would otherwise be best suited would perform poorly if it stood on a common screed surface of the rooms to be separated. But I would leave such matters completely unemotionally to the specialist planners; as a (co)investor / initiator, one can already "deal sufficiently" with the usage concept.

But I would leave such things completely unemotionally to the specialist planners,...

What do you mean specialist planners now? It's the ideal expansion shell for hobby craftsmen. The walls are already standing...

Isn't that the ideal expansion house for hobby craftsmen.

Yes, of course, styrofoam shuttering blocks with popcorn additive in the concrete filling

It currently looks very much like the existing building is going to be renovated after all. However, gradually. Well, I have little say in this decision. I would rather be in favor of a rushed action so that money flows back quickly, but okay.

In any case, the planner now stated that the 60cm(!) thick brick walls of the building no longer meet the energy saving ordinance. Insulation would still have to be added outside. That really knocks me off my feet. It’s just a simple brick wall, okay. But 60cm isn’t enough? On one side it’s even 65cm. Could he be right?

In any case, the planner has now stated that the 60cm(!) thick brick walls of the building no longer comply with the Energy Saving Ordinance. Insulation would still need to be added on the outside. That really blows me away. It's a simple brick wall, okay. But 60cm is not enough? On one side it’s even 65cm. Could he be right?

Oh, is there finally a planner now? - until now it was only a "consultant." Let me put it this way: if you enter only a wall thickness into an Energy Saving Ordinance wall construction calculator without knowing the structure and exact materials, it will always output "something needs to be added." In principle, you can create thermal bridges from almost any material with a little design flaw, then no amount of thickness helps. But so far I had the impression that people talked a lot who didn't really care about a factual basis. Do they actually want fees for their talk?

That's still the same guy. What should I call him? Mr. X! I looked at this lambda calculation. I have to study that later. In any case, this wall is very simply constructed. There's only the bricks. Nothing else. Later there will be plaster on it. But he knows that. And we want to eliminate thermal bridges - like windows, for example. No other thermal bridges are known, it's a solid block. He'll definitely want a fee. So far, no invoice has come in. I've already said they should be careful and also talk about consulting fees. We'll see.