Timber sizes and spacing for a monopitch roof on timber outbuilding

[John D v2.0]

Breathe membrane might not do anything depending where it is, should be on the cold side of any insulation with ventilation to outside on the cold side of the membrane. You could put a vcl on the warm side of the insulation. However if there is no insulation or heating then it's going to have condensation regardless.

 

[StoneColdSteve]

Thanks for all the advice. So having taken into account buildings regs, proximity to boundary etc the clear span of my roof will now be 2.9m. Will 6x2 or even 4x2 rafters be suitable as I think 8x2 may be overkill?
I've also decided to stick with cladco roof sheets and ensure shed is well ventilated to hopefully negate mass condensation.