Steel Roof Tips
 

I recently had to re-roof an old house, and chose painted steel. To reduce the footprint created, I was careful to use both sides of the diagonal cuts and generally avoid scrap, and I used sawmill scrap for the strapping.
Information on how to put steel over shingles is hard to come by. The manufacturers don't want to discuss anything but all-new work, and the YouTube videos are somewhat contradictory. Doing it this way, I was able to do it all myself without risking disaster, and the old roof is still there for backup and insulation, etc.
If I were doing another house, I'd know a lot more about how to do the strapping in ways to make the rest easy, and various other tricks. Let me know if you have queries.

I put a metal roof on my house nearly 20 years ago and never regretted it. The panels are actually polyester powder coated, not painted. I used 2X4 pressure treated sleepers over the asphalt shingles and shimmed them to account for settling.

My roof is a light gray. My neighbor installed red panels about a year after I did mine. There is some fading on both colors but not a speck of rust anywhere. My neighbor changed the screws on his roof two years ago and I will be doing the same this spring. The rubber washers are cracking and the screw heads show some rust where the drill driver chipped the coating. It is a one day job and costs less than $100.

The biggest surprise I got was how much cooler it made the attic in the summer - at least 20F at mid-day. I was also preasantly surprised how the sound of rain on the roof puts me to sleep at night.

I cannot imagine ever having asphalt shingles again.