Facade discolored after 4 years

Ok, thanks. Now I also know that there are differences.

How and with what to correct? I also read about a water-repellent coating.

Really many thanks for your effort and time!!!

half a year later...

An expert with their own laboratory examined three "core drilling" samples and came to the following result:

According to the expert's statement, the applied plaster build-up does not correspond to the one required in the specifications. This requires a (high-quality) medium- to thick-layered plaster system with a layer thickness of 15-18mm (of which 10mm is top plaster). What was applied was a rather thin-layered plaster system with thicknesses of 4.5 to 11mm. The applied plaster thicknesses significantly influence the resistance to fungi and algae; the facade has significant microbiological infestation.

Furthermore, a functionally different plaster system was used. The specifications called for a 10mm "water-absorbing" top plaster, but "water-repellent" was applied. The expert explained the differences between the systems in that the dew point of the required system lies within the plaster, whereas in the one used, it lies on the outside. "We ordered a Porsche but got an Opel."

In addition, the high-quality paint applied (silica sol silicate) does not fit this plaster system and its only function is to "adhere."

When asked about renovation options, the expert could not suggest any solution. (He previously worked himself in a development department for plaster systems).

Good (or not) ... we will now report this as a defect through our lawyer.

What renovation options do you see?

Greetings and have a nice day!!

What renovation option do you see?

Option. Singular, not plural. Remove the plaster and redo it.

Which renovation options do you see?

One of my fellow volunteers often says: "A dog can have both lice and fleas at the same time." I mean: Improper execution is one issue (lice), the other is that white plaster, even when done perfectly, is not suitable for every situation (flea). The Koll music school in Kaarst had the same problem. Multiple times. Ultimately, they solved it with a large-scale graffiti. No infestation is noticeable anymore, and it has looked good for years.

For other reasons, the plaster was redone after 3 years. In coordination with our construction supervisor, a bonding mesh was applied to the old plaster and then replastered on top of it. I don't know if this could be a solution for you.

I had problems with algae and similar stuff (mostly greenish but also dark/black) above a ventilation outlet. I sprayed Geiger 09 on it. Afterwards, you could practically watch the algae and co become invisible. It has now been over a year and so far nothing has come back. However, it is of course not exactly environmentally friendly and bleaches various materials – you have to be careful that it only gets where it is supposed to. I suspect that other products with the same ingredients would work just as well, but I only know this one.

As a long-term solution, this is certainly not for you. But at least with this you could quite cheaply check whether algae and co are part of the problem and let that flow into the selection of the new solution.