I'd like to get/give some input on building a coop for a half dozen Rouens that summer on a 150' x 75' pond and will winter on a 25' x 20' pond with dock deicer bubblers to keep the water open. A natural brook feeds these 2 man made ponds, so they stay clean. My cats and dog may have helped keep predators away, or I've just been lucky. We made it through last winter without a coop, but I think it would be great if I could train them to go inside at night. As it is now, they will come over to within 4 feet of me when I put out some feed on the lawn next to the pond, but that's as friendly they get with humans. It'll be some task to get them into a coop once built. I'll use the feed as bait.
Back to coop design: I'm thinking a 4' x 6' footprint on stilts about a foot tall. Lift off roof, and lift up back wall for easy cleaning. Also for easy cleaning I'm thinking of using some high grade plywood on the floor that is designed for outdoor sign making. It has a very smooth water resistant finish but exceptionally pricey. 24" interior headroom.