The existing roof is laid directly on purlins on about 3 centers with no roof deck.
Re roofing a barn.
The original form of metal barn roofing is made from tin.
Unroll the felt a bit at a time working from left to right making sure the felt is flush with the edge of the roof.
This is the least expensive form of metal roofing.
Position the roofing felt at the bottom left hand corner of the roof.
The existing metal sheet is not in super bad shape but is definitely pretty rusty in some areas and is curling up in others.
There are several different types of metal that can be used to replace a barn roof.
However a tin roof will have to be replaced sooner than other sorts of metal roofs.