Moist aerated concrete exterior walls: First interior plaster/screed and then ETICS?

Hello everyone,

we were unable to seal the flat roof of the penthouse, and now it has been raining for days. This is causing water to partially get into the house, but due to the lack of an eaves, the exterior walls (Klaksandstein) are also getting wet.

The roof is supposed to be sealed after a few dry days, and by mid to late this month both the interior plaster and the screed are to be installed in the house. Afterwards, the moisture in the house should be dried out and then, before it gets too cold, the [WDVS] is to be attached from the outside. The idea behind this is to allow the moisture to escape through the walls as well.

Now I am wondering whether this even makes sense. Currently, it rains more often, so the walls are getting wet from the outside, and as far as I know, not that much moisture can be transported through the stone. Wouldn’t it then make more sense to first seal the roof, then install the [WDVS], and only afterwards do the interior plaster? That way the exterior wall would no longer get wet, which would also protect the interior plaster from, e.g. frost.

What do you think? What are the pros and cons of each option, and which would you tend to choose?

cheers, MG