First of all, you should build a regular rafter by cutting at 60-degree one end of the 2×6 rafter and then by using sandpaper to make it smooth. Then you have to build a bottom rafter from a 2×6 lumber this is done by cutting with a saw at 30 degrees the both end of the beam. Now, you should lay all the components on the surface with no gaps.
You can learn more about the construction of the 16×24 gable shed, get it here.
As a support, you will use 2×4 lumber. Now, you will cut one end of support at 60 degrees, after cutting allow to lay down on the surface.
Now, you will make a 1/2” plywood gussets for covering the joints. By leaving no gaps, insert 1 5/8” screws, so all the components become tightly closed. These are the trusses. For attaching the siding panels, you need all these supports! You will fit 1/2” plywood and attach to the rafter by 1 5/8” screws and regular trusses produced. Fit the trusses evenly at the top of 16×24 shed place and install them evenly at a distance of 24” from the center.
Then use the level to plumb it and lock it in place by tying them with the top plate. For professional work, you should cut by T1-11 siding, the end panels, and then by using 6 to 8d nails secure them into place tightly.
Now assemble the overhangs of the shed front and back by using the rafter and 2×6 blockings. You will make holes in the rafter by drilling and then insert the screw of size 3 ½”. Now, you will fit the overhangs. It must be fitted over the shed front and back portion. The edges should be aligned and drill hole and insert screws of size 3 ½”.
Then for the roof sheets, you will use the ¾” plywood. Lay down on the roof all the panels after cutting at the right size. The edges should be aligned, and drill hole and insert 1 5/8” screws, and lock it into place along the rafter at every 8”. You must produce a professional result by no leaving any gaps.
At the side of the shed fit the 1×8 trims. Then align the edges and drill hole and insert brand nails of size 2” to lock tightly the trims. For the 16×24 gable shed front and back, build the trim. You can set the trim into place by aligning the edges by inserting brand nails of size 2”.
By roofing felt cover the roof and make sure that strips should overlap by 2”. You should use the tar paper to secure the plywood sheets. Also, for the top ridges use a large piece of it. Now, over the roofing felt fit the side drip edges and fit the bottom drip edges under it.
Before installing, you should carefully read the instructions written on the asphalt shingle packs. Install them by starting from the left side of the roof to the top.
If you are looking for a complete guideline to build a gable shed you can visit this site.