I'm planning to redo the roof on the barn soon. It's an old tile roof on lock plank. Two of the sections have rotten beams 15.5x12.5cm, 360 long. The boards are probably rotten too, so just with these, 6 out of 9 meters will have to be torn off... So... The plan is to tear off everything under the roof or at least assume it's needed. The idea is then to put new boards on in the same way as before and lay sheet metal. I'm a bit concerned about the sizing though... It's 3 meters between the trusses and 160 cm between the beams that lie on the trusses, and then 25mm plank on it. It's held with tile, so it should be fine with sheet metal. But if I put new "cheap wood," 21mm standard panel from the nearest building supply store with feather-light boards compared to the old sturdy boards, will it really be okay??
I've also been pondering back and forth about whether to put the sheet metal directly without any fabric/masonite or something or not... Currently, I'm leaning towards just putting the sheet metal... I guess that's okay as long as you don't plan to build anything insulated inside??