ᐅ Interior partition walls showing horizontal cracking

Hello, how is it possible that almost all non-load-bearing partition walls in my house have developed horizontal cracks overnight? The walls were built using 11.5 cm (4.5 inch) and 17.5 cm (7 inch) hollow concrete blocks. I know there are wallpapers that can hide these cracks, but I am concerned about the bathrooms that will be tiled. The structural engineer says these cracks can be caused by the sagging of the ceilings and are not a cause for concern. Should I believe that?

Oh God, the house is collapsing. This is typical—everything was rushed and put together too early.

The partition walls were plastered 12 weeks after the masonry work.

The structural engineer is actually the expert and should know this.

The crack itself can, of course, represent a visual defect if it exceeds a certain width (there are limit values, I believe over 0.2 or 0.3 millimeters (0.008 or 0.012 inches)).

If you are building with the general contractor, they will probably say that the painter will fix it ;-)

And when painting is done as owner’s work, the construction company will also mention that.
Plaster cracks are effectively and permanently covered by painting fleece or wallpaper.

And what about the bathroom? It should be tiled up to the ceiling.