Building a jig on the shed floor to make sure all the rafters are exactly the same. nailing on the gussets. this is the fourth video in our shed building series.. Test the shed roof rafters by putting them up on the shed walls and verifying the birds mouth cuts.if you are happy with the rafters then you are ready to use them as a template to build the rest of the shed roof rafters. build enough shed roof rafters to have one set at each end and then every 24" along the shed walls.. Make sure all truss are the same or else you will not have an even roof. 2�4 rafter (a) measures 6? 7 1/4? with 30 degree miter cuts on both ends, same direction (see illustration above)..
Calculate the length of the rafters. the length depends on the pitch of the roof. rafters sit perpendicular to the long side of the shed, so they must be long enough to cover the width. measure the width of the shed between the outside of the exterior walls and divide that measurement by 2. next, consult the rafter formula chart.. This step by step diy article is about how to build a roof for a 12�16 shed.after building the base of the shed and fitting the wall frames, you need to continue your project by fitting the rafters and the rest of the roofing components.. How to build shed roof rafters 2. step 1: mark and cut the first rafter ends the first step in building the roof rafters is to cut one rafter board to length with the ends angled properly and then to mark and cut the birds mouth and seat on the rafter..