Problems with moisture in exterior plaster

Good day dear forum members,
I am new to the forum and have registered to inquire about your opinions, assessments, and assumptions regarding a problem with the exterior plaster of our house.

We built in 2017/2018.

[*]2 full floors
[*]Flat roof
[*]Geothermal energy
[*]Solid construction, 36 cm Ytong blocks without additional insulation
[*]Exterior base plaster is a fast-setting lightweight plaster based on lime-cement with mineral lightweight aggregate. Suitable as an undercoat for mineral top plasters, especially for heat-insulating wall materials, e.g. porous bricks, aerated concrete, etc. The base plaster was applied on 28.9.2017. The finish plaster was applied on 24.10.2017.

You can tell... I go into detail about the plaster. The attached pictures also explain why. The base plaster was applied about 15 months ago now.

After it rained, the effects shown in the pictures appear on the house facade. The areas that appear/are so massively damp are those places where there is still Styrofoam insulation applied on the Ytong blocks (ceiling anchors, roller shutter boxes, concrete ceilings, etc.).

My assumption is that the plaster does not have the weather-resistant properties it should actually have. At the places without Styrofoam, the Ytong block absorbs the water directly, and at those places with Styrofoam the water is not absorbed or is "held" by the Styrofoam and thus visible on the facade. This would mean, conversely: the facade lets water through.

But... I am an amateur and this is only my assumption.

In addition to the damp spots, small white spots / efflorescences have recently appeared on the facade.

My question to the experts here: What do you think of this? What do you think could be the cause?

Thank you very much for your help!
Best regards
Hawe01

Ui looks bad

What does the cleaner say about it? It doesn't look normal to me either. Unfortunately, I can't say more about it due to lack of expertise.

hello Hawe01 since we currently have the same problem with [Porenbeton] I came across your request while googling. Do you have a solution by now? It would be nice if you could give me a hint. Thanks

Hello , in the meantime our house has been replastered and the defects have been completely eliminated.

In our case, it was a combination of various problems and errors:

[*]No reinforcement mesh was applied – not even on the weather side of the house.
[*]Materials from different manufacturers (Sakret and Schwenk) were used for the base and top coat plaster. This is unusual and against the manufacturers’ recommendations.
[*]Contrary to the manufacturers’ recommendations, no primer was applied on the base coat plaster. Primer serves to equalize the water absorption capacity of the different substrates. Without primer, sand separation and cracks can occur.
[*]The exterior paint of the house was a silicate paint instead of a silicone resin paint. Silicate paints have a significantly higher water absorption coefficient. In our case, this meant that rainwater penetrated the facade and in those areas where there was insulation (Styrofoam), the water could not enter the Ytong and was thus visible on the facade for a long time. The silicone resin paint now used ensures that much less water can penetrate at all.

Feel free to send me photos of your facade.

Regards
Henrik

They really ignored the simplest basic knowledge of plastering.