We build several buildings for the South Dakota Department of Transportation for sand/salt storage. They ususally use our 60 foot truss on ten foot rafter spacings. They require and enginered standard of 90 mph wind loads and 65 psi snow load. Like Andy said the snow usually just slides off, and really there isn't much for the wind to get ahold of baecause it simply drafts over the roof. Depending on the size and style of the building our snow and wind loads can be anywhere from 90 mph wind to 140 mph and snow loads from 65 psi to 160 psi. I have seen a 50 truss barn with at least 10 foot of snow drifted and curled over the top of the barn. It never moved, sagged. That barn is at my home place and I have pictures of it with the snow on top I will see if i can find it a post it for you to see. I think you will be quite amazed.
