I don't like this style of coop for some reason, probably mostly because you have to duck down under that shelf which drives me crazy and makes it seem smaller to me. I've never gotten a solid opinion out of any of the residents, but they seem fine with it.
On this one, the only solid walls are in the box where they sleep, but even it still has a vent along the back side. Also a couple of the back siding boards flip down to allow us to get in and scoop the shelf from the outside. In the winter, we use a piece of household paneling and cover the front of this shelf, leaving one end exposed so the can get in and out. Essentially TRULY creating a box out of the top shelf.
The door is made from a discount plastic house shutter, I got two of them for I think $5 because they were dinged up. It's a narrow door but we fit well enough so it works great!
The shelf is household paneling ontop of a couple of 2X4s and the wire was to keep them out of their poop before I realized they would perch in both directions therefore not always pooping over the covered part! Well, we're going to just take that out, because it's mostly just in the way. The chickens don't hang out up there at all, it's just a place to sleep and we usually scoop it before they go to bed so it's no big deal.
Well, I hope this will help you get some idea of how easy it can be to make a chicken coop. If you have a predator problem, or have an extremely cold climate, obviously these choices will not be right for you.