What is the purpose of fascia boards compared to cladding

[TullioK]

I'm rebuilding a flat roofed garage and am wondering what the point in fascia boards are here because the rafters don't overhang the wall, instead they finish flush with the edge of the wall. Is there any reason I shouldn't clad right up to the roof line?

A rubber roof will be installed with a gutter along the edge in question.

Thank you

 

[^woody^]

Cladding is just one fascia board on top of another

 

[big-all]

you need free airflow around timber and your roofing material needs timber to attach to so you need a transition from horizontal to vertical so in general will be your joists plus an overlap as the transition from timber to render or brick