saggy rafters

[jason]

i'm installing steel roof on my older home there are only one layer of shingles so to save myself time and money i decided to strap over top of the shingles with 1+4 strapping only one problem my rafters are bowing vertically from the peak to the facia some spots 2" i wen't into the attic and braced the rafters to support the load of the new steel but was considering tryin to jack the rafters back in place and realized it mabee a bad idea don't have the time or money to replace the whole roof rafters and all any ideas?

[HayZee518]

my thoughts on it is they rafters were installed "green" and over time they dried out. Like beams they should have been installed with the camber facing upward so as they cured they'd bent down. possibly some of yours were installed the other way and when they dried made the camber more pronounced taking with them the sheathing and the roofing. jacking them won't help. if you could loosen up the nails holding the sheathing maybe you could "sister" up a piece of 2X6 to that rafter and bolt it into place. no need to nail through the roofing paper and sheathing, the mere weight of the roof and new roof will hold eveything together and you won't have that sagging effect.