External construction supervision for expansion in Erkner, seeking recommendations

Good day, we want to build a solid extension onto our timber frame(?) prefab house. For this purpose, we have obtained architect offers. We have also received an offer for service phases 1-8. Is it recommended additionally/instead to have an external expert and if so, which one is recommended? Thank you very much!

Take a look at the [IHK], you can find good sworn experts there. It doesn't hurt to have someone else take a look as well.

Good evening, thank you very much for the tip, we will take a look. Should such an expert be involved before signing the architect's offer (we have not received a contract, only an architect's offer - is that sufficient?) and for the entire duration of the construction project additionally or only for certain phases of the project? Sorry for the naive questions, this is all new territory for us. Best regards

I would inform the architect that the construction is being supervised by an expert. And to be honest, I would have them come by 3 to 4 times during the relevant phases (foundation slab, shell construction, roof, for example). Many also do this through the [Bauherren-Schutzbund].

we did not receive a contract but only an architect's offer - is that sufficient?

Certainly.
even online sales and also services: whoever accepts or commissions an offer creates a contractual relationship.

So we also received an offer for performance phases 1-8. Is it recommended to additionally/instead hire an external expert, and if so, which one is recommended?

No. Do you know what the architect's performance phases include? I already wrote to you in another forum. Performance phase 8 is the external construction supervision – and more comprehensive than any expert can do.

Good day, we want to build a solid extension onto our timber frame (?) prefabricated house. For this, we have obtained offers from architects. So we also received an offer for performance phases 1-8.

First of all, be clear about exactly what and how you want to build. Of course, you can commission all performance phases at once. But that also directly means that you want to build with separate trade contracts.

Should such an expert be involved before signing the architect’s offer (we have no contract but only an architect’s offer – is that sufficient?) and for the entire duration of the construction project, or only for certain phases of the project?

Not at all. In the morning, the architect is on the construction site controlling construction, organizing the trades, checking invoices and construction progress, coordinating rectification of defects – and in the afternoon the expert should come by again?

I would inform the architect that the construction will be supervised by an expert. And honestly, I would have this expert come by 3 to 4 times during the relevant phases (foundation slab, shell construction, roof for example). Many also do this through the Homeowners’ Protection Association.

Then take performance phase 7 as the last phase? And who exactly will do the other tasks from performance phase 8? The original poster, who has no construction knowledge, takes care of invoices, progress, defects?
: Engage more with the topic and your wishes and goals. Then decide whether you want to take the architect completely, possibly have only the planning done by him and then commission the general contractor, get involved yourself (supported by the expert), or proceed however you want.
Many roads lead to building a house. Also consider why a solid extension should be added to a timber frame prefabricated house – I initially see that as nonsensical. The connection of a timber frame extension to the existing building is actually the logical solution.