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Cracking

Cracking

Cracking

(OP)
Does anyone know if drywall expands and contracts with changes in relative humidity?
I am trying to diagnose the cause of a crack in a perimeter bulkhead ceiling of drywall that was installed about October of last year. It is a long narrow (about 3 feet wide) strip of drywall ceiling bulkhead and the crack originates at a point where the drywall ceiling was notched out to accomodate a building column; the crack extends across the 3 foot width and then up the vertical drywall face of the bulkhead. I am trying to diagnose the cause and then to suggest a repair. The jagged crack does not appear to be at a taped joint. Possible causes that come to mind are one or more of: a) expansion and contraction of the drywall with changes in humidity in the room from fall to winter combined with the stress concentration caused by the notch; b) perhaps the ceiling supports in this location were placed too far apart; c) deflection of the concrete flat slab floor above due to live load on the floor above (I don't think this is very likely because the floor above has fixed auditorium type seats).

So - does anyone know if drywall expands and contracts with changes in relative humidity?

I am also interested in any ideas of how to fix the crack so that it foes not occur again.

RE: Cracking

And I do think gypsum board sheathing contracts when drying out over time. There typically are control joints specified for long, long interior walls and I've seen cracks near doors when this is not done.

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