I can help you calculate the amount of material you will need to build your trusses.
How Do I Calculate The Lumber Size For A Roof Truss?
15mm sould do it so long as you do a birdsmouth next to the hip joint every 300mm
I'm adding onto my shed. The addition is 8 feet wide. The truss will be 11 feet long where it ties into the existing gabrel type roof. What size lumber should I use.