As high as possible. The problem is that the grading system (G4-1, G4-2, etc.) primarily considers the presence of knots. The most important characteristic of exterior cladding is that it is densely grown. No problem in Norrland, but almost unsolvable in southern Sweden. G4-2 corresponds to the old V sorting (fifth sorting), which, considering the quantity and nature of knots, is the lowest acceptable for exterior cladding. Preferably move up to G4-1, ideally in northern Swedish spruce. I guess V+ is the same as G4-2.C Crayo said:
Widely grown cladding has greater lateral movements, which leads to gaps and poorer adhesion for paint.