Facade discolored after 4 years

Hello everyone,

I am aware of the difficulty in getting a clear answer through a forum and thus remote diagnosis on the topic of dirty / discolored facade, but maybe with your help I can still make a little progress.

We are already involved in a legal dispute with the construction company responsible due to some other defects (base “dissolving,” soaking wet external casings, etc.). However, our lawyer advised us on this issue to have the facade repainted at our own expense, as only an elaborate and expensive laboratory investigation can actually clarify the cause.
We will still have a master painter come to us; maybe he can determine the cause.

Facts:

[*]Single-family house

[*]Facade paint 4 years ago, nighttime temperatures around freezing, according to the construction company three coats of paint

[*]Partially no roof overhang present

[*]Edge flashing

Facade construction:

[*]Insulation material mineral wool

[*]Reinforcing mortar water repellent

[*]Top coat water absorbing

[*]Silicate paint hydroactive (biocide-free)

(Hope this is all correct!)

At first, I suspected the edge flashing; meanwhile, I think it is a combination of facade paint and flashing. The facade below the gutter is also dirty; at places with a roof overhang, there is no dirt.

I have a few assumptions but will keep them to myself for now, but I already have two questions:

[*]If you run your hand over the silicate paint, it powders finely, very finely. Is that allowed?

[*]I do not trust the construction company at all; I also do not believe the claim of three coats of paint. Can this be easily verified? How does the quality or ability (to whatever) of a facade paint (except coverage) change with multiple coats?

Of course, I will also post pictures of the facade here.

Thank you very much, hopefully for some answers!

Many houses on the west side have this problem. It is especially noticeable on white houses. In many cases, it is also around ventilation outlets.
This is usually not dirt, but algae or fungal spores or something of that kind, if the spot is regularly wet from rain or condensation.
At some neighbors of ours, someone came by and applied some expensive miracle product against algae/fungi, and after a few weeks the spot was completely white again. However, they then ordered cheaper stuff against the fungi themselves and sprayed it on the house side. It worked just as well.

Many houses on the west side have this problem.

More north, but with all the characteristics you mentioned.
Our new development area is characterized by this - some more, others less... depending on how each has insulated their house or which plaster was used.
For these factors:

Facade paint from 4 years ago,

Silicate paint hydroactive (biocide-free)

a very classic phenomenon.
.
For us, it started after 7 years. Not paint, but colored plaster with biocides.

Rather north

North as well, but in our residential area, for the houses where it is very noticeable, it is rather the west sides, because the rain tends to hit the wall more often there due to the west wind. However, it may also depend on the roof shape and roof overhangs.

Good morning.

6 houses in the neighborhood, two solid remaining prefab houses.

3 have severe infestation by now. One homeowner has even cleaned and painted.

One tried to hold the prefab house manufacturer liable, without success. Various paints with different quality standards were offered; during the selection process he could choose whether to use Algizit and fungicides, he did not choose them and therefore did not get any rights.

For these houses, it is the west side, but there is also the forest; the north side also shows signs.

So far, we have been lucky, no discolorations.

Hello,
thank you very much for your participation and analyses.

The possible discolorations caused by algae growth on damp exterior walls, especially on the north and east sides, are known to me.
For this reason, we also decided on silicate paint, as it has a high pH value, is nutrient-free or low in nutrients, and of course biocide-free. If I remember correctly, we also chose it because it is often used on old buildings, such as churches, etc.

I attached the photo with the scaffolding for the reason that one morning early, when the sun was shining obliquely on the facade, I noticed a bright, almost unstained horizontal stripe, which I then also found on the long side of the house. I think I can recognize that exactly between the scaffolding planks a touch-up was done, and on the right, where the crossbeam ends, it was rolled further upwards. I think you can clearly see the "roller marks"; no idea what that is called. The technical data sheet of the manufacturer states to paint wet-on-wet.

Therefore, I would be interested to know whether the paint coating only works properly when applied at least two or three times.

It is also read that silicate paint silifies due to the ingredient potassium water glass and is thus inseparably bonded to the substrate. Why then does the paint powder off? Outside temperature during painting?