New floor construction, what would be recommended?

Residential and commercial buildings are classified as "Altbauten" from 25 (usage) years onward.

Dear KlaRa, now me: unfortunately no! The term Altbau is linked to age and construction style. Usually up to the early 1950s. Then come the Altneubauten, then the Neubauten. This is based on the architectural style. Sorry, and now back to technical topics!

Old building is not an exactly defined term. It's that simple. In Berlin, in common parlance on the rental market, "Altbau" means before World War II and "Neubau" means after. In the Rhineland, Altbau is associated not only with an old house but also with a high ceiling. 25 years of use is just as legitimate a description as the reference to architectural styles – there is no "right" or "wrong."

The uzin site (Turbolight) seems to be down – : would other lightweight screed variants also work?

The uzin site (Turbolight) seems to be down - @KlaRa: would other light screed variants also work?

Your note is correct, however, I am also unable to answer the question of WHY. Certainly, there are similar alternative special constructions to "UZIN-Turbolight," e.g., from Schomburg with "ASO-EZ light." At the time, however, the lower surface weight was decisive for the commitment to the UZIN system, as according to the structural engineer, the ceiling constructions at a 13 cm height build-up were only allowed to weigh a maximum of 85 kg. And this with a surface load of 5 kN/m² and intense public traffic.