Proper Ventilation/Drying of Interior Plaster / Drying Time

Which floor insulation do you mean?

The screed insulation. That is, the Styrofoam boards that are laid under [Fußbodenheizung] and screed.

For interior plaster, regular airing by opening windows briefly should generally be sufficient. Continuous window ventilation can cause drafts, which leads to certain areas drying faster than those in the wind shadow in the corners. This can cause cracking. The interior plaster is on average only about 1 cm thick, but due to the large surface area, high humidity develops. The masonry dampens the release of moisture.

Be careful with "technical ventilation." Dehumidifiers -> yes. Heating blowers or gas heaters -> no. Burning gas creates moisture, which is then pushed into the walls by such high-performance blowers, leading to uneven moisture distribution and potentially causing cracking.

Do you have "only" the bitumen waterproofing membrane between the base slab and the first course of bricks, or additionally a masonry barrier between the first and second course?

If you have spoken with a building drying company, what does the expert say about the issue of 25 cm flooding?

I’ll just add to this old thread. Would it be helpful during the drying of the interior plaster to tilt a window at the bottom and at the very top of the house and then set up a small heater with 1-2 kW? Could this cause any damage to the lime gypsum plaster? Apart from the fact, of course, that the rather small heater might have only a homeopathic effect.

Insulation can be installed and, as already mentioned here, ventilate by shock three times a day. The moisture in the plaster is not the water used for mixing; it is the result of the chemical reaction, which is completed after 28 days. From then on, it will get drier. By the way, it also helps to occasionally wipe the drops off the frames with an absorbent cloth. Every half cup of water counts. Technically, drying only occurs after 4 weeks; otherwise, there will be cracks.

I am currently having very good experiences with window vacuums for windows and water bead spots on walls (plaster). It is important to give the plaster/screed time to cure. The released water should then be removed outside through air exchange and "vacuuming/wiping".