We designed a coop after several others on this site. There are some excellent ideas! We decided to go with a stilts design for under-coop space utilization. The birds have their dirt bath there and keep out of the rain as well. It is also nice for access all around (for cleaning, feeding, etc) since we don't have to bend over. We used a home-built sled to move the coop to it's position in the yard. It is built for 12 birds, in hopes that we can add three new birds each year as the older ones stop laying. We live in MN and although we've read that the coop doesn't have to be insulated in our climate, we decided to insulate anyway. We used a technique called SIPS (structural insulated panels) that made the walls very strong and that was a plus. They are 2x4"'s layed flat with 1.5" foam insulation glued on one side to the 1/2" OSB and on the other side to T-111 exterior. The roof is Indura (a recycled rubber product). The general dimensions are about 4' x 6'. The nesting box is shingled and provides exterior access to eggs. The run was made from re-purposed fencing materials already on our property. We still need to add chicken netting to the top of the run (to keep them from flying out when they're not free ranging), and planting boxes to the inside of the base of the run. We didn't build the fence into the ground for predator protection, so the planting boxes will keep vegetation in the run, keep it from being too muddy, and stapling the boxes to the fence will keep predators from digging in. We keep food, water, grit, and oyster shells inside. We have a ladder-style roost but the birds prefer to all squeeze onto the top rung. We also use the deep litter method for bedding.
Afterthoughts: Now that the -25 degree temps are setting in in Northern MN, we're having trouble with eggs freezing and cracking. We took some extra insulation pieces and taped them around our nesting box, as that's the only area of the coop we didn't insulate. Wish we would've considered that earlier, but it is an effective fix for the winter months. Also, having more than one interior outlet would've been good for these cold days as well, since we run two heat lamps in this cold. Our deep litter method is working well, but we only have about 3-4" of depth in the coop. Higher doors would be nice to get the litter to a depth of 6". Still, we have no ammonia odor and haven't cleaned the coop out for 6 months. We stir it up, but the chickens do the rest.