Sagging Roof
Nadine has a problem with a sagging roof in Atlanta, Michigan. Here's her full report:
"My roof is sagging. I never realized my rafters are 27 and one-half inches on center. The roofing material is is made from metal squares.
What can I do to make the roof flat?
Look at the photo of the underside of my roof."

This is the underside of Nadine's roof. Those look like homemade trusses with the wood splice plates. Very cool! Photo credit: Nadine
Here's my answer:
Nadine, it's pretty simple.
I'd just climb up in the trusses and add 2x4 blocking in between the top cords of the trusses.
You'll get great results if you place them 32 inches on center.
Be sure you consider drilling pilot holes in the ends of the 2 x 4s so you don't split them.
If the ends split, they don't have as much holding power and strength as they should have.
Tim built custom homes and did ultra-custom remodeling for 20+ years before launching his Ask the Builder media presence. He was selected as one of the Big 50 by Remodeling magazine in 1993. This award gave birth to Ask the Builder in October 1993. Tim also operates https://DrawPlumbingPlans.com. His @askthebuilder YouTube channel was the first home improvement channel on YouTube.