When I first built my coop, I figured 32sqft would be enough space for a chicken run. I imagined some of our six hens would be inside, while others would be outside. Turns out, that wasn’t the case because the chickens like follow each other. When one goes out, they all go out. I quickly found myself needing a bigger run, especially when the chickens reached full size.
I designed and built my chicken coop on my own, based on a rough sketch I drew on a piece of paper. To make it as simple as possible, I used 4×8 foot pressure treated plywood for the floor, and basically built the framing upon it (lumber comes in 8 foot and 12 foot lengths). The legs raise the floor about 3′ off the ground, and underneath the plywood floor is where I originally designed the chicken run. Once complete, it was easy; I just installed welded wire around the bottom and that provided 32sqft of chicken run.
However, as noted earlier, I realized this wasn’t enough. Within the first year, I added 64sqft, but ended up adding an additional 64sqft the next year.
There were a couple thoughts that lead me to my decision. The first was, I read online that each hen needs a minimum of 10sqft. At 32sqft I was way under, and with 64sqft I was right at the minimum threshold, especially when I added in the water and food feeder. The second thing was, based on a few of the chickens behaviors (jumping on each others back), I suspected they were feeling claustrophobic. When resources are scarce (to include living space), chickens tend to bully one another for dominance. It can lead to pecking issues where they will pull each others feathers out.
Adding additional space wasn’t too difficult in both instances. For the first expansion, I built an 8×8 foot caged in area connected to one of the sides of the chicken coop. For the second expansion, I created another 8×8 foot caged in area connected to the original expansion. In total, there is now 160sqft for the six chickens. Some will say this is more than enough, and perhaps even overkill. That may be, but I had the space in my backyard so I figured why not. I can also increase my flock size by 3 hens with no problem.
To answer the question of how big a chicken run should be, I would say 10sqft per hen is on the small side. I’d recommend 15sqft per hen. If you have 4 hens, that would be 60sqft of space, or just shy of an 8×8 foot enclosure. Yes, you can get away with smaller, but just keep an eye on the chickens behavior to see if they are bullying each other. Be very weary of the online chicken coop kits. Many indicate they can support 6-8 chickens, but they only have a 20sqft run! That’s definitely too small for that many hens.