Vaulted Ceiling 21% pictch

[stuartpetty]

Quick question, im buying an extension and I have a vaulted ceiling with a shallow pitch of 21%

My question is this, shall I board horizontal across the rafters or Vertically ?
Many Thanks

Stuart

 

[flynnyman]

Across and stagger the joints

 

[jesssop]

Horizontal

 

[malc]

horizontal, the strength of the plasterboard is in the bonded edges.