I'll throw my 2 cents in. On one end I would box it in.Say 4'-6' feet deep. Put nest boxes on the back side for easy egg collection. Put a door for humans as well as chickens. Don't put a threshold. It makes it easy to sweep/shovel stuff out if there isn't a board across the bottom of the door opening. In this new boxed area rounded 2x4's bleacher style for perches. The wide 4" board lets them stretch and covers their feet from frostbite. I would put a window in each end for a good cross breeze for summer and solar warmth in winter. If using windows take out screens and screw hardware cloth to the inside wall across the window using flat head screws and washers. It wont keep bugs out! But the screens clog up very fast and the air goes bad, making for sick birds. The wire keeps everything else out so you can open your windows
. I found that the simple things like being able to take the perches out make for faster cleaning. For us we are still working on ours. We just need more concrete board and a closet door. Money funnels to the chickens last LOL. We have hang out the back nest boxes. It added perch space inside our box. We also put a rounded 2x4 channeled across the front of the nest. So on cleaning day I open the coop pull out the perches and the boards in front of the nest boxes and power spray them. Dry in the sun. I have a small flat shovel that fits perfect in the nest box. I open from the front and shovel everything to the main coop. Rake everything out into a large bin, sweep and either mop it or power spray it. Winter gets a quick mop summer gets a soak down. Mites like to hide in the corners and cracks of everything. After all is dry I will seven dust cracks and corners and put hay back down.
You are lucky and already have a concrete floor. The hard part will be drilling into the it to erect the frame. As for the rest of the area chicken wire and make a door for you and chickens if you want them to free range. Chicken wire will not keep out a hungry raccoon, coyote, or other determined critter. That's why it is good to have a safe house inside the run. A strong chicken door.
One day last fall I had my chickens in the run. I didn't free range them that day too much ice/snow. But I didn't close up the coop door. I lost half my flock that night. Something climbed over the top and chewed the wire, and walked right in to the coop. My fault for not closing the hatch and thinking the chicken wire was enough. I replaced that wire with hardware cloth and haven't forgotten to close the hatch again. I need a hatch on a timer LOL.
I have a 10'x20' kennel with broody hutch for a grow out pen.
I have bird netting across the top. I had a hawk get trapped in it last year.
But not before he killed a teen.
The back side of my coop/run. The glass in the window comes all the way off. Leaving just the wire on the inside. One the real cold days we had this winter,
I stuffed an old comforter between the window and wire, to help insulate the window.
My coop has insulation between the walls and expand-a-foam sprayed around the boxes.
I put a 100 watt heat bulb out there and while it was 0 the coop was at 28. Not great but no one froze.
The nest box has 6 nest in in with dividers. 3 on top 3 on bottom. I made the bottom set 2 inches shorter than the top.
Some of the girls like more room than others. But most fight over the bottom left one. Not sure why they are the same size on the bottom.
Hope this gives you ideas. If you want more details i can take closeups ect..
