How far apart should rafters be spaced on pergola if used for training grapevines?
I plan on building a metal pergola to train a total of 2 grape vines. However, i need advise on how far apart the rafters should be spaced and if weather the vines should run perpendicular to the rafters or in line. Plus, do i need slats on top of the rafters? If yes, then how far apart should they be spaced? Also should the rafters run along the longer side of the pergola or the shorter side? The pergola would be 18 ft long by 13 ft wide and 8 ft in height.