Structural engineer needed for rough assessment of load-bearing capacity

It is not yet entirely clear to me what your core concern is: do your doubts relate to the cellar in general, that is, whether it could support a stone house at all when it only had to be designed for a wooden house; or specifically to the cellar after the fire event, whether it could previously have supported a stone house and was not fully "utilized" with a wooden house, and after the fire a new wooden house would already be the limit? A structural analysis proves the stability of the construction project (already done back then), a verification analysis checks whether the structural engineer correctly calculated the actual structural analysis (also already done back then). After that came the fire event. Its damage report should have addressed whether the cellar still has the same structural suitability as before the fire – I already said about that

I do not expect the cellar's suitability to be impaired; the fire was apparently above, and "only" smoke gas and extinguishing water affect the concrete less.

. The new house definitely needs its own structural analysis again, basically using the cellar ceiling as a foundation. The structural engineer will say where supports still need to be placed in the cellar rooms if now load-bearing walls are planned above the cellar ceiling in different locations than exist in the cellar itself or were considered for the previous house. I would therefore much more expect limitations on the freedom of the floor plan layout of the new house rather than have fundamental concerns about building a stone house. You can use aerated concrete; it does not have to be the heaviest sand-lime brick plus facing brick.

thank you, yes, that the new house will then be statically calculated again is clear - but that will only happen in the planning phase.

I'm still not quite clear about what your core concern is: are your doubts generally about the cellar, that is, whether it could even support a stone house while it only had to be designed for a wooden house;

exactly about that, that the cellar was designed back then for a prefab house from 1980 and therefore we are not sure if it is even suitable for a solid house. I think the issue of "fire" is now settled. The cellar was not affected by that :)

So far we have only been to one solid house builder. Because he said directly that he would at most put a aerated concrete bungalow on it, we continued to look into wooden construction methods.
More recent discussions with architects and a master carpenter about a 1.5-story house gave us hope again, because according to them their construction methods "are not really lighter than some solid constructions."
That brings me to the current thread - although I just noticed that I could have continued the old thread.

Timber frame construction definitely works on the old basement.

The structural analysis must be done by the contractor anyway. So you will pay anyway.

Timber frame construction definitely works on the old basement.

The structural analysis has to be done by the contractor anyway. So you pay either way.

Yep, but just recently we talked with a wood architect who builds very thick walls, filled with cellulose and uses wood fiber boards on the outside. He said that’s not a problem but also not really lighter than some solid construction. That’s why we’re now wondering whether we should take another look at the "Massiv" option.

That's why we are now wondering whether we should reconsider the "Massiv" option.

My opinion: there are reasons to build a prefabricated house, and there are reasons to build a solid house. For me, it is obvious to choose a prefabricated house here, simply because of risk minimization. Personally, I would not choose a heavier option if I had the choice of a simpler or more obvious option that does not present any other disadvantages.

Don't let anyone tell you otherwise. 1 m2 of exterior wall weighs roughly 2.5 to 3 times as much and interior walls 3 to 5 times as much in solid construction.