Originally Posted by Wuzzat?
If you can stand >180F replace the boards piecemeal from underneath by removing wood and sistering the patch board section with the support board, a 2x2 or a 2x4 on edge. The patch board and the 2x4 should have a tee cross-section.
Take care your fasteners do not penetrate the metal roofing.
If you get the same deflections then your patches are strong enough.QUOTE]
You are kidding aren't you, have you ever done a repair like this?
Nobody answered in 7 hours and these last posts are not really answers.
My bad, wrong mental image. . .
If each between-rafter section of the rotten board is 22-1/2" long, then a 2x2x22-1/2 goes between the rafters and long screws are angled up through the 2x2 and up into the rafters to support the new 22-1/2" board.
For less added weight use an aluminum channel, U shaped or rectangular.
I never had to do this repair, not yet.
Structurally I think it should work but I welcome a "design review".
I'd think the worst part, besides the heat, would be climbing over the roof trusses while avoiding protruding roofing nail points. So, wait till fall. Meanwhile, get in shape, 'cause this type of work is stressful, dirty, physically demanding and can be dangerous.
What do you suggest for the OP?
He doesn't seem too hot on climbing on this roof.