General procedure / schedule

Find an architect who plans the whole thing as a timber frame construction. I am fairly sure you will face fewer exclusions and dependencies than with a prefab house provider. If you still want to try it, we have had good experiences with Gussek Haus. You would just have to clarify how the Kfw40+ works if the photovoltaic system does not come from them. Basement construction by the builder is not a problem, nor is the garage. I would be interested to hear your feedback on price negotiations afterwards; it’s not like construction companies have too little work and would have to concede a lot.

To me, that sounds like a valid approach.

What I mean is that a basement commissioned through a prefabricated house supplier and accordingly outsourced costs 10-20% more than a basement I would commission directly from the basement builder.

That would be the case if you take a supplier who builds from the finished floor slab upwards, but I wouldn't take such a one anyway. However, the 10-20% you save at that point you have to spend again on a planner.
But actually, I didn't really talk about that. I meant more that you want to change contracts and insert some additional clauses and renegotiate and so on.

That is also something I want to know. The planning is done for the entire house, including the basement. That means the costs for planning the basement are not charged separately again. If I am mistaken, could you please specify exactly what you mean by that. I just haven't read up enough on this topic yet.

Oh well, I mean that if, for example, the construction performance description states that the scaffolding must be provided by the client, then I would have that changed. There are points that are very unusual but also unknown to some homeowners, and these are all extra costs. Only points that are not correct are raised, as it varies more by construction company and the risk distribution is often not fair.

1. Are you looking for an architect/energy consultant, or does an architect from the prefab house company take care of that, even though the basement, photovoltaic system, etc. are externally ordered?

If you buy from a prefab house supplier, they will sensibly also provide these services.

2. Looking for an expert to simply support us during construction. Should we rather take someone from the Bauherren-Schutzbund or someone like the "prefab house expert"?

These "prefab house experts" seem suspicious to me; I do not see a significant difference to a "construction expert," nor any special required additional qualification for prefab houses. We had none on hand but a lot of presence and clear construction meetings.

So first prefab house supplier, then basement builder, then photovoltaic company, then finishing carpenter, then stair builder?

You need the plans for a basement/stair offer; these are created by the architect of the prefab house supplier. That also determines the sequence.

Decision on prefab house company and revision or extension of contracts such as the scope of work description through additional clauses and everything that is not fairly balanced.

There is little reason for prefab house suppliers to agree to contract changes. Do not expect any significant negotiable changes regarding anything related to the manufacturing process.

Then the price negotiation. Should one also seek professional help here, and if yes, who?

If you don’t want to appear as an insecure and incompetent customer from the start, do it yourself.

Signature and starting signal for the house construction. The architect should already have the floor plans etc. ready for the building application beforehand.

You won’t get that much upfront service from a prefab house supplier. Alternative: Take a local architect and a local carpenter who also offers "turnkey" solutions. They have a good reputation in the area to defend and therefore anticipate more interest in success. You want to have a lot of input; that is possible there. Therefore sequence: Think about how you want to live instead of what. Find an architect who is really enthusiastic about your project and get started.

We have a supplier's market. The company will tell you there are no changes. Apart from the fact that you are causing yourself trouble with the coordination between the basement builder and the house builder. if something goes wrong, it was always the other one

That is also something I want to know. The planning is done for the entire house, including the basement. That means the planning costs for the basement are not charged separately again. If I am mistaken, can you please specify exactly what you mean by that.

If you have an external planner, you don't need a prefabricated house supplier. If you let the prefabricated house supplier plan everything, you don't need to outsource your basement externally. You are a bit misinformed and focused on something you first need to let go of.