I have been reading all the "experts" are saying it is the top member aborbing moisture. The long expansion from very dry to very wet is .1%More than likely in the winter it is too dry up there.
Hand framed rafters may come into contact with a ceiling joist over the wall but that is about all.I know "zero" about trusses, so let me ask the dumb question: why doesn't this happen to stick-built houses? After all, once it's all nailed together it is essentially the same thing???
That is the theory. Have you seen any studies that prove it or tell you what the force is? I can't find anything that sounds scientific.Truss uplift varies on the climate. A big difference geographically.
In the cold, dry north the uplift effects come from the bottom cord that is buried and covered with insulation. That minimized the temperature effects, so the diagonals a much colder in the winter if there is good ventilation above the ceiling insulation. - This leads to the diagonals and top chords becoming shorter and pulling up the total truss upward, causing the cracks in dry wall joints.
It is worse on the interior walls because the temperature effects are a little less than the exterior walls there the trussed a held in place better.
It is a little different where the temperatures and are more constant.
Any truss will move with loads, temperature and moisture.
In the hall way there should be no screws in the ceiling close to the wall.I can see it in my hallway, it runs perpendicular to the trusses. The drywall lifts where the wall and ceiling meet. Comes back down in the summer. You can just see the tape pulling, doesn't leave a crack, most people probably never see it. In hind sight, there are a few things that I would do different.