Drywall on OSB boards, cracks?

Vapor barrier does not mean that the OSB does not absorb or allow water vapor to diffuse. Nor is that the purpose. The materials GK and OSB simply behave differently. Since an architect is involved, he must plan according to the approval of the state building code anyway. Just look at the approval; the layers are specified exactly there. What is not tested will make little sense.

Our neighbor has the combination. Unfortunately with "wrong", non-vapor-tight OSB. Cracks everywhere after switching summer/winter/summer. Massive. Arguing with the expert and drywall installer.

There is no water vapor diffusion dense OSB, which would also be nonsense. This is only about a vapor retarder and it depends on the Sd values and the layer thicknesses or the water vapor diffusion equivalent air layer thickness, which should decrease towards the outside.

The possible cracks are indeed annoying, but "harmless". What is important is that it does not start to mold ...