Splash guard around the house - tips

What did they do wrong?

After my expert harped quite a bit on the topic, I suspect it’s the missing connection between the building waterproofing (=foundation slab to masonry) and the base coat. Usually, there are insulation panels in between, and if water gets in there, a capillary effect occurs at the joints. Then water is drawn from behind into the plaster.

I came across this scheme and it makes me somewhat thoughtful. Accordingly, a mineral sealing slurry must be applied again up to above the GOK. Structurally, the execution with us is identical to this drawing.

Sorry, I completely misunderstood your question or the problem, even though you had explained it clearly. The way it is shown in the drawing is correct, i.e., sealing again up to about 5 cm above the ground level.

I have meanwhile been able to consult my expert on the subject and he stated very clearly: An additional moisture protection must be applied on the base plaster up to 50mm above [GOK]. However, many reject this for aesthetic reasons, as it is inevitable that this material transition will remain visible after the final coating.

50mm seems a bit tight to me. But for aesthetic reasons, I would anyway raise the base significantly and paint it in a contrasting color to the facade.