Interior construction KS/brick/metal stud frame

Good day everyone,

I am new here in the forum and hope I am posting in the right subforum etc.

I have bought a condominium which is currently being built. Since I come from a different engineering field, I don’t have much knowledge about interior construction/static engineering and have only read about it roughly so far. It is about the following: the builders have sent us a letter with the following content (not verbatim):

For structural reasons, the non-load-bearing interior walls cannot be made of calcium silicate brick (the building description states calcium silicate brick or brick). Consequently, the interior construction would have to be done with bricks with a bulk density of 0.8 kg/dm^3. Alternatively, a metal stud frame (10cm w110) is explicitly recommended without additional cost to us.

First of all, the question is whether the reasoning is that conclusive; according to my research, calcium silicate brick is somewhat heavier than brick, but that should not be such a big weight difference for the narrow interior walls whether it’s calcium silicate brick or brick.

Assuming that all this is correct, what do you think about the recommendation for the metal stud frame regarding soundproofing/stability/mounting of wall cabinets etc.? The letter mainly highlighted the advantages of the metal stud frame compared to brick (ws111 better sound insulation, better mounting, easier remodeling, etc.).

I have researched, ws111 is the simplest version (single layer). How is the price difference to brick and calcium silicate brick? Shouldn’t brick be significantly more expensive, is this just an attempt to save money? Is calcium silicate brick more expensive than brick? Is brick much worse than calcium silicate brick?

Calcium silicate brick was my clear favorite, so this is naturally annoying now. I would be very happy if an expert here in the forum could advise me on what would be the best choice in my situation and how to assess the matter.

Thank you very much in advance.

Best regards

Robin

Addendum:

Of course, I meant w111 above. Furthermore, I was informed about the sound value of 45dB compared to brick (41dB). After looking at some tables from Knauf, I come to the conclusion that it must be a very simple design (based on the sound value of 45dB). This also directly brings me to the topic of fire protection. What is prescribed for a fire resistance class? Partition walls (according to Paragraph 30 of the building code) are specified in our building permit as F90-AB, does this correspond to the non-load-bearing interior walls?

Are you then also not allowed to set up heavy shelves? Strange reasoning from the [Bauherren].

I have also wondered about that, a bathtub filled with water or something like that should therefore be a problem. Is it possible/allowed to review the structural calculation?

One could suggest using plasterboards. But a developer who is not a complete novice should not need to be brought to that idea. Does your contractual arrangement allow for other options than losing the interest?

Are all affected interior walls within your own apartment then or do some of them also border other apartments or communal areas such as the hallway?