"This area will eventually be finished for living space."

Jerry,

Relative to the ceiling rafters that will become floor joists, I plan to sister each member with a new joist in the areas considered "living spaces". Since the old joists are rough sawn, this will also help provide a more level floor. With a center ridge height of only 8"-8" and an 8.5:12 roof pitch, much of the floor area will not be used. We added two shed dormers with a 3:12 pitch to provide adequate height for two bedrooms. These rafters are 2x10's with a 12" gluelam ridge beam. The new bathroom is centered over the center supporting wall. Only part of the original 2x6 rafters will require a finished surface. The ridgid closed cell foam insulation acually stiffens the roof structure, but I have not seen any valid data on this, so it's just a bonus.

John Lampert