Underlayment and also Steel Roofing-- Metal Roofing 101 with Todd Miller
https://sethqvie209.edublogs.org/2020/04/03/specifying-spf-roofing-systems/
You will certainly need to get adequate metal material to cover the entire roof, as well as this process starts with gauging the full dimension of your roofing (in square feet). Snap chalk lines on the roof covering