The best replacement for rafters is trusses.

The best alternatives to rafters are rated as following:
★★★★★  trusses
★★  joists
★  truss
★  joist
★  roof trusses
  ceiling joists
  purlins

Your alternative for rafters is not listed? Suggest!
Speaking about rafters, one probably shouldn't forget about trusses.

Other search terms related to rafters and their ratings are:
★★★★★ trusses
You have in mind a companion for rafters and it is not yet here? Propose!



Google Trends

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rafters
trusses
joists