It sounds reasonable but these are really questions for an engineer,
I would have expected at least 2x8 rafters for strength and insulation.
Nails have real good shear load strength so don't count out the nee walls as being support or not, that is still an unknown what an engineer was thinking. The ceiling joists were just nailed too and there were doing what ever they do to support against wind or snow loads, what have you as well as the ceiling.
I would consult an engineer but this is what I would be looking for him to approve.
Sister 2x8 on the rafters and set at least a 2x8 floor joist on top of that. Then I would consider the insulation for the upper part too.
I would have expected at least 2x8 rafters for strength and insulation.
Nails have real good shear load strength so don't count out the nee walls as being support or not, that is still an unknown what an engineer was thinking. The ceiling joists were just nailed too and there were doing what ever they do to support against wind or snow loads, what have you as well as the ceiling.
I would consult an engineer but this is what I would be looking for him to approve.
Sister 2x8 on the rafters and set at least a 2x8 floor joist on top of that. Then I would consider the insulation for the upper part too.