
The solutions to condensation / moisture control are typically:
1) Reduce moisture levels inside the building
2) Ventilation in the building and the space beneath the roof
3) Insulation to help prevent the migration of warm air from the inside to the underside of the roof.
4) Vapor barrier such as polyethylene to help stop the migration of interior moisture to the back side of the roofing.
You do have a challenge on your hands with animal confinement, a pretty airtight building, and no decking beneath the roofing. I would try to accomplish as much of the above as possible. Fans running inside the coop can be helpful at stirring the air up a bit as well.
I live in the UK in Norfolk.
I've had a new chicken house built of concrete blocks and a metal sheet roofing. The problem is the condensation soaking everything. Will fibreglass wool between the joists and a chipboard ceiling which I have at hand stop the condensation or should I also attach a plastic membrane (above or below) the wool?
I don't want to remove the roof sheets unnecessarily as it's a large construction not a small coop.