The joists are 2x8s spaced every 48". The span is 22' with no support in the center. The rafter system is spaced on 24" centers. The existing joists are sagging significantly in the center with no additional load on them other than the roofing system. I expect that I will need to at least add additional 2x8s to re-space them on 24" centers, but would this be sufficient? The previous house that I lived in had 2x8s doubled up with 1/4" steel flat bar sandwiched in between to span the garage. Would this be the more appropriate solution?
Please advise any help will be appreciated.