This was a lean too a year ago. Nothing was square or planned on it - ugly but manageable. I took what it offered and closed it in with raw lumber, added a front door and a horizontal rectangular floor door in the rear to let the birds out daily in the fenced summer run. We also added a winter run to the right with a polycarbonate roof which I hope generates heat in the winter and allows the bird to scratch around in the dirt here in northern Michigan. Last winter they just sat in the coop all winter and got frost bit - not good. Only one bird (EE) went out in the snow (cowards). As you can see, its just thrown together from a bunch of scraps. It has a plywood floor with a heavy duty tarp over it. There is also nesting boxes inside. We just winterized it also. We'll likely decorate the front next year and we still have a days work left. We'll add horizontal vent screen to the front and rear for airflow. I'll post more later and read what I post first - oops.
Built a gray mobile coop also.
1. Built a frame and internal supports for a floor and it was eyeball leveled with 2x8s
2. Screwed down a 1/2" plywood floor.
3. Bought a Super Heavy Duty Tarp and stapled it over the floor to prevent rot. It has worked for the past 3 years thus far.
4. Went to the amish lumber mill and bought thick 8' random type slab wood.
5. Measured an old external door and built a frame for it in the wall.
6. Went to Lowes and bought two small windows and built a wall frame for them.
7. Built a frame in the back wall for a low horizontal door.
8. Built a frame for the winter run on the side.
9. Then I closed it all in by screwing down the Amish lumber side by side until it was completely enclosed - nothing fancy.
10. Put on the door and painted it.
11. Then I decided we needed a winter run so I added two posts to the outside to create a 3 sided enclosure and a sloping roof topped off with a polycarbonate roof. Does not generate heat in the winter, but gives the chickens an area to scratch around in all winter w/o the snow.