Open the link in my signature to get my ideas about how much room you need. I don’t believe in magic numbers for much of anything to do with chickens and I don’t give you any. We keep them in so many different conditions that one number cannot cover us all. I just try to give you some things to think about and reasons you might need more or less room. I do believe in going bigger rather than smaller. I find that I get fewer behavioral problems, have to work less hard, and have more flexibility in dealing with problems if I do not crowd them.
Fur or feathers will insulate an animal, at least to a certain extent. And the animal has to be grounded for the electric fence to work. Dogs, foxes, skunks, coyotes, possums, bobcats, and who knows what else are so used to going through a barbed wire fence a strand electric fence will probably not slow them down much. Wires closer to the ground will help a lot but I would not want to depend on it that much. But it will help. Many things like fox or coyote can easily jump a fence but the tendency if they meet a barrier like a mesh wire fence is to stop and investigate it. Most of them investigate with a tongue or nose. Once bitten they tend to not come back but there are always new ones being born so you can’t let your guard down.
There is another problem. The chickens can go through that fence and get outside of the protection. If they touch the fence with their combs or wattles they will get shocked but their feathers will insulate them if their heads don’t touch. They will probably not fly over it, just walk through. Baby chicks especially are bad about his.
I don’t know how your fence is set up, but I’d look real hard at how to attach something cheap like chicken wire on the inside to form a physical barrier to slow down the predators and keep the chickens inside.
One big problem with electric fencing is that weeds and grass will grow up in it and short it out when it is wet. Whatever you do, keep the maintenance of grass and weed control in mind. I use electric netting and use round-up to stop the grass and weeds from growing but some others won’t like that method.
For that many chickens you need a walk-in coop. About the easiest way is to go to Lowe’s or Home Depot and get a prefabricated building. Those are really not that hard to set up as a pretty good coop but they are not real cheap. You need to add ventilation, roosts, nests, and a pop door. A window too if it doesn’t have one. Those are really not hard. You probably need a foundation of some type too so you get it off the ground to prevent rust and to tie it down so the wind doesn’t blow it away. That can be a concrete foundation, brick or cinder blocks mortared in, 4x6 treated timber or other ideas. The goal is to have a solid barrier animals can’t just walk under a low spot, prevent rust, and tie it down. The foundation may be the most work in one of these prefab buildings.
It is less expensive but more labor intensive to build your own. If you buy new building materials most come on 4’ or 8’ dimensions. If you can incorporate that into your design you can usually build a coop with a lot less cutting and fitting and with less waste. If you have other material handy consider what you have when you come up with sizes. Often on Craigslist you can find a building to buy cheap that you have to either relocate or tear it down and get building materials.
One easy way to stop animals from digging into a coop or run is to make an apron. Instead of burying the wire straight down, lay it horizontal on the ground around the coop or run and attach it to the bottom of the fence or wall. You don’t have to bury it but just weight it down with boards, rocks, or something so the grass can grow through it and hold it down, but if you remove the turf and put that over it, the wire is protected from lawn mowers and weed eaters. About 18” is plenty. The idea is that an animal goes up to the fence, starts digging, hits the wire, and does not know to back up.
I suggest you lock them in a secure coop at night. It’s a lot easier to make a coop predator proof than a decent sized run. In spite of what you may hear, many predators can be active during the day, but the night is your most dangerous time. Many are more active at night and you don’t have human activity at night to scare them away. They have a lot more undisturbed time to generate mischief.
I find a predator-resistant run to be quite handy. There are times I don’t want them out roaming. You can make a run pretty predator proof if you spend enough money and put in the labor, but it is really easy for there to be a weakness somewhere. Something is better than nothing.
How big does it need to be? I have no idea of the absolute minimum you could get by with. If you build it with fence posts and welded wire you can make it fairly big fairly easily and without a great expense. If you build it out of lumber and hardware cloth and cover it, the costs and labor involved go way up.
Flying predators are rough if you don’t have a roof over everything. I had an owl go into a grow-out coop one night when I was late locking them up. We’ve got all kinds of big hawks around here and I saw a bald eagle just a few days ago, but that owl is the only time I’ve ever lost a chicken to a flying predator. I know others have. You can read many different things people do to try to discourage flying predators. The only one I try is to have a few places the chickens can run to if they sense a bird overhead. That might be bushes, small buildings or structures, or even an old satellite antenna a bit off the ground if you want to get that trashy. For foxes, coyotes, dogs, and raccoons I’d think hard on electric fencing.
We all have our different predators and predator pressure. Often the problem turns out to be something we did not expect. Be flexible and good luck with yours.
Was thinking with the bottom 4 strands being only 4 inches apart that might deter the animals. I know it will my dog (he won't step foot inside the horse pastures). Not sure I can afford the expense of a fence around the whole 100X100 feet. Was thinking that if they were outside of the fenced area and my dog or a fox went after them they would know where safety was? So maybe just let them out while I am around?
