Box beam gable framing new gable overhang is framed in the form of a box beam hanging off of a new layer of roof plywood roof sheathing cantilevered over the top of the 3 layers of rigid insulation.
Roof overbuild framing.
Use of rafters trusses and a truss base polyline are demonstrated architectural home design software.
1 8 pitch is given so 24 x 1 8 equals 3 or unit of rise in inches.
Or if you want to raise the roof a bit more install fascia around the roof perimeter attached to the new soffit and nail the new roof deck to crown molding above the fascia.
If the unit of rise in inches is 3 then the cut is the unit of rise and the unit of run 12 inches or 3 12.
The exposed edges of the 3 layers of rigid insulation are no longer exposed.
To provide a framework for the new trusses nail 2 by 6 inch strips of wood around the perimeter of the roof.
Below is a link to a roof plan with a section that is over framed see note 3.
Figure 2 2 roof framing terms.