ᐅ Problem with Base Plaster – Microcracks?

Hello everyone,

I am facing a puzzle – and unfortunately, so is our site manager. The basecoat plaster was applied last summer. It was quite hot at the time. At first, everything was fine. After a while, these whitish discolorations appeared. We pointed this out to the plasterer, who applied another coat. However, that only lasted a few days.

Now the questions are: Does anyone know what might be causing this? And what could be done about it? Should I consider hiring an independent building surveyor?

Unfortunately, I don’t know which plaster or paint was used, but I will ask the plasterer.

I now have the information about the plaster and paint. A lightweight plaster called Knauf Sockel Lup was used. The paint was Knauf Autol Premium Silicone Resin Facade Paint with Self-Cleaning Effect.

Do you have a photo of the same spot during the shell construction / before plastering? What type of masonry do you have? It looks like a liquid is seeping out through a gap (joint) and causing efflorescence on the surface.

Well, the foundation slab is actually supposed to be there.

It looks like the plaster is efflorescing, but the pattern does seem unusual. Is there no base sealing applied at all?

We built with Poroton. There is a red rubbery sealing compound applied on top.