Roof replacement advice needed

[KennyG]

If you don't add trusses won't you get sagging?

If the new rafters are sized for the span, they will support the roof. However, in this situation you can get by with undersized rafters by adding a short "knee wall" halfway up the roof. That cuts the span in half. However, I thought the original description said there were design problems with changing the roof slope?

 

[jimmyj]

Sagging won't be an issue, the existing trusses are good and strong. My original thought way back was to "sister" some 2x 10's alongside the existing trusses in such a way that they were aligned at the bottom but the new boards were gradually higher as they approached the ridge. But, that would require all sorts of other changes to the gable ends and other stuff so it's too much of a pain.