ᐅ Do all construction materials need to be available when the structural engineer prepares the calculations?

Hello!

Our architect has commissioned a structural engineer to carry out the structural design for our single-family house on our behalf.
We had always been considering a Poroton T8 block. We even thought about choosing a T7.
Now we’ve received the structural calculations, and everywhere they refer to T9. This block has a higher bulk density, so it should be somewhat more load-bearing.
Is it necessary for all the details of the house to be finalized and clear before the structural engineer prepares their calculations? Or is a small safety margin usually assumed? It does make a difference whether ventilation ducts are installed in the intermediate ceilings, thermal building component activation is implemented, or underfloor heating is laid. All of this will also affect the structural design.

Thanks in advance

Well, the structural calculations (including the review calculations) are part of the building permit / planning permission and must be finalized beforehand. Load-bearing elements must not be altered later by openings or penetrations. However, underfloor heating does not cause any issues in this regard. Of course, materials can be changed, as long as they do not affect structural components.