When you are building a shed, it is important to remember that the roof structure can be exposed to extreme loads if the area where you live receives good amounts of snow.
You will want some assurance that when you build a shed roof that it will stand for many years and protect the shed contents. Therefore, when buying your shed plans, check that the roof construction will be to the standard you require and that it complies with your local building codes.
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Having checked that your plans are at the right rating for your area you can then go to your local lumberyard and order the roof trusses you need.
Once you have taken delivery of the roof trusses, you will need to mark the top plate of the shed walls every 24 inches on center. Sit your first roof truss on the first mark and nail into position. Repeat this action for the rest of the trusses.
Many roof designs have a 5/8" decking that ties the trusses together, which supports roof loads. Install the decking, then cover with asphalt roofing paper and clad with roof shingles.
Deck the roof on a calm day. If you attempt this in windy weather, you run the risk of being swept off the roof as the wind catches the large flat roof surfaces, which can act as sails. It is a wise move to get help when putting up the trusses and the decking material.