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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.

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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.

  • So in the case where a wall partition (running parallel to joists) is right below or right next to a truss cord, then what should I do in terms of fastening at this point? If I don't attach to the truss cord right next to my wall, then I have 24+ inches of floating drywall and if I do attach, the only floating edge of drywall is roughly 2 to 6 inches max. There seems to be no perfect method, then? – Nic Jul 31 '17 at 22:02
  • I do not think there is anything wrong with up to 24" of unattached drywall. It will be attached continuously at the joint with the partition. – Jim Stewart Jul 31 '17 at 23:17
  • Sheet metal "corner back" angle or individual clips are used along the top of the wall for drywall fastening. It gets nailed to the top plate before the wall is hung. You don't want the drywall to be unattached completely. – isherwood Sep 8 '17 at 19:55

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