A historical replacement included backing and fascia
Our Dublin record from August 2013 describes removal of synthetic cal-shake, new backing and sheathing, and eight ventilation vents before the replacement shingle roof was finished. Wood work included three fascia boards, gutter fascia across the front of the second story and several overhang boards. The old material dimensions in that record are historical, not a current design specification. For a new job, the exposed condition and issued permit determine the repair and inspection plan.