Originally Posted by
charles buell
That said the adjacent roof trusses have to have been designed for the adjacent roof overlay----and you will rarely see any design change in the adjacent roof trusses to compensate for a "typical" overlay
That's it exactly. The underlying trusses will see roughly the same loads as they would without the overlying roof (plus the dead load of that overlying roof structure). BUT, instead of the loads being distributed over the roof surface, these loads have been converted to point loads on the trusses. Trusses typically must be designed for point loads such as this.
That said, I doubt the infill framing will overstress the top chords of the underlying trusses. But that is not a call that I want to make.