Problem with base plaster - microcracks?

In the meantime, as recommended, I sent the pictures to Knauf. There was a prompt response with the offer that a representative would come by and take a look. So we made an appointment with the builder, plasterer, and Knauf.

The representative said that these are microcracks through which liquid penetrates. Due to the sunlight, the effect of which is further intensified by the anthracite color, the water evaporates again through the cracks. This then causes these efflorescences.

Knauf's proposed solution: repaint with a fiber-reinforced paint in the same tone on one section of the base. We agreed on about 2 meters in length. If this solves the problem, then the entire base will be painted this way. If efflorescences occur again, the entire base area would be treated with citric acid to combat the efflorescences and then the fiber-reinforced paint would be applied again.

I will keep you updated

Hello Baraja,

I probably have the same problem: south side, anthracite and microcracks with efflorescence. In addition, there is no roof overhang on this side, meaning it is exposed to the rain without any protection. Our house is almost 10 years old and we are now experiencing a moisture problem on the inside for the first time at this spot.

Unfortunately, there also seems to be a thermal bridge at this location, so the surface temperature on the inside at -5 degrees outside is only 15-16 degrees. I am therefore not sure whether it is condensation or moisture that has penetrated.

Has painting with the fiber-reinforced paint helped? I would then also like to try that in the summer.

Many thanks in advance

The entire base was painted with the color. We then followed the recommendation to switch from anthracite to a light gray. Here, I saw a small point of criticism in that new light efflorescences are hardly visible on a rather light (concrete-like) color. What spoke in favor, of course, was that it is less sensitive to sunlight.

In the area where gravel and flooring were applied, I sealed with mineral sealing slurry (Knauf Sockeldicht), and before that came the obligatory studded membrane.

So far, I have not seen any more cracks. Something seems to have worked.