The roof structure rises by almost 2 cm upwards!

Yvonne, you are right. But look at the pictures. That is too much. Something is not right. The story about the OSB boards also seems strange to me, but these boards have something to do with it, bet? My construction carpenter insisted on tongue and groove for the floor here. He rejected the boards as unsuitable. He did not say why. Karsten

Karsten, I checked: with us it's partly, especially at the corners, similarly wide. The screed shrinks and the walls are attached to or built on the screed. The ceiling is fixed at the top... We were warned during construction that something like this would happen!

The cracks are already quite large.

Can you say something about the process?
At what temperatures was the upper floor built, when was it painted?
Was it already heated at that time?

The roof truss is made of KVH? Wooden battens under the drywall?

The roof truss was built in December 2016 during dry cold temperatures. It was not heated at that time. The drywall ceiling was installed in June, and painted in July. Yes, the roof truss is made of KVH. I am uploading a picture of the attic... The drywall is screwed onto the wooden battens.

Just to note: it is normal for the ceiling in the upper floor, i.e. drywall, to separate from the wall. ... Therefore, if the painting work is done in EL, you eventually have to use acrylic.

Is it really supposed to be the roof structure? [emoji15]

The cracks appeared relatively quickly, at first they were much smaller and the site manager also told me that this is normal, they would fix it in spring without problems........But as I said, now he says that this is not normal and these big cracks appeared because of the OSB panels.....2 workers would do it, takes about 2 days but costs around 1000 euros including travel time etc.

Yvonne, you are right.
But look at the pictures. That is too much. Something is wrong. The story about the OSB boards also seems strange to me, but these boards have something to do with it, bet?
My carpenter insisted on tongue and groove boards for the floor here. He rejected the boards as unsuitable. He didn't say why. Karsten

Because OSB acts as a vapor barrier, and if there are leaks in the lower foil, moisture can accumulate and cause mold under the OSB. Otherwise, however, it is common to use OSB as a top layer.

Two statements confuse me.

If installed in summer, OSB should contract in winter rather than expand. In summer, humidity is higher than in winter.

In addition, OSB 3 boards do not absorb moisture from the air. I built a ramp for the stroller out of the boards. It is exposed to the weather without any further treatment and does not swell.

Because OSB works as a vapor barrier and if there are leaks in the lower foil, moisture can accumulate and cause mold under the OSB. Otherwise, it is common to use OSB as a top layer.

Two statements confuse me.

If installed in summer, OSB should contract rather than expand in winter. Humidity is higher in summer than in winter.

In addition, OSB 3 boards do not absorb moisture from the air. I built a ramp for the stroller from the boards. It is exposed to the weather without further treatment and does not swell.

Hello Joedreck,

I agree with you, two colleagues of mine also told me the same, that OSB tends to contract rather than expand in winter.......