Chilli,
How cold does it get there? It makes a difference. I had laying hens for 10 years and winter in New England can change your design.
I had a man door facing east and a hen door facing west. I had a 10x12 coup andthe walls and ceiling were insullated.
The building was up off the ground with mesh wire from under the skirt boards to 16 inches into the ground to keep preditors out from under the building. The floor inside was 3/4 inch plywood with 2 inches of concrete poured over it.
I also had a caged in area out back covered in tight mesh wire on the sides and top, and the mesh went 16 inches into the ground. The area was 12x20.
The feeder was hung off the ceiling and I had two sets of commercial nesting boxes on the walls. I had 20 nests and that will accomodate 60 hens fine. The waterer was on a stand on the floor.
I used lights on timers (16 hours of light) to keep the girls laying. I also ran infrared heatlaps in the winter. They layed all year round.
Pine shavings in the nest boxes is the best. Hay is very bad and can cause respiratoy problems ( mold) in the birds.
I used coarse saw dust for floor bedding from a local sawmill.
I would recommend a roosting bar in the coup, about 2 feet off the floor. It's best to provide space for the birds to roost off the floor . 12 inches of roost space for each hen.
Hope this helps.
Regards,
Chris