When running ceiling drywall (sheetrock) on the main floor, it is screwed to the truss chords. I have read on here that when there is a partition wall in the way, to just let the drywall float and have the wall board support this un-secured end of the ceiling drywall. The reasoning was because otherwise there would be a crack from truss movement.
Does the same idea not counter-argue the idea of letting drywall on the ceiling "float" at the corner seam from ceiling to wall transition? After the top corner is mudded, and the trusses lift up, it would lift the ceiling drywall which is mudded to the wall drywall, therefor causing a crack, correct? I'm having a hard time finding the proper information that is not contradicting physics.
Best Answer
In the field of an expanse of ceiling drywall nailed to the bottom cords, the drywall can rise with the chord and bend, but at 16" or less from a vertical partition one stops nailing to the bottom cord so the cord can lift without pulling the drywall with it. The drywall must be allowed to bend in this last 16" because at the intersection joint with the wall the ceiling drywall is joined to the wall drywall which cannot lift.