Going to put in some soffit in WBP ply. Previously always used 9mm ply, as trussed roof centres were at 600.
On this cut roof centres are at 400 .... is 6mm ply good enough, i.e won't sag between fixings ? or do I need to use 9mm
Reason I would like to go with 6mm is that I would probably need to cutback the rafter horizontal cuts a bit more if 9mm use :-(