2 is the obvious answer if the shed is 12ft then at 4 and 8ft to join the boards onjmc67 wrote:Yes, planning on one window on the front Big-all, and I'll be running 2 or 3 beams from the front to the back to support the roof.
Good to know on the preservative Mike - will do that bfore the whole thing becomes immovable.
now assuming you need around 4 to 8" each end for overlap start at 1 end with the 5ft odd[plus overhang] panel so the first timber will be around 3ft 6 in from the end wall the next one will be at 4ft centers with the last span filled by a board and a bit length ways side to side with a join towards the back top wall using a bit off off cut ply/roofing material or 2x1" baton inside