Nearly every problem people have with a backyard flock traces back to the same root cause, and it is almost never the one they suspect. Feather-pecking, bullying, egg-eating, birds that will not go in at night — these are crowding problems. Not feed problems, not breed problems, not bad luck.
Chickens sort out a pecking order the way every social animal does, and they need enough room to get away from each other while they do it. Take that room away and the order gets enforced with a beak.
The numbers
| What | How much |
|---|---|
| Coop floor, per standard hen | 4 sq ft |
| Coop floor, per bantam | 2 sq ft |
| Coop floor, per large breed (Orpington, Brahma) | 5–6 sq ft |
| Outdoor run, per bird | 10 sq ft |
| Roost bar, per bird | 8–12 in |
| Nesting boxes | 1 per 3–4 hens |
| Nesting box size | 12 x 12 x 12 in |
| Ventilation, per 10 sq ft of floor | 1 sq ft |
| Pop door opening | 12 x 14 in |
| Feeder space, per bird | 4 in |
| Waterer space, per bird | 1 in |
Round up rather than down. Every one of these is a working minimum, not a target.
Why four square feet, and when it is not enough
Four square feet per standard hen assumes the birds get outside every day. If they do, the coop is a bedroom and a nest box and not much else, and four is genuinely fine.
If they are shut in — deep snow, a stretch of hard rain, a hawk working the neighbourhood, or the weeks after you have seen a fox — four square feet is tight. Birds confined to the coop for days need closer to eight, and this is the situation people never plan for when they buy.
That is the argument for a covered run. A run with a roof keeps the flock out of the coop in weather that would otherwise shut them in, and it solves a problem that only shows up in February when it is too late to build anything.
Roosts: height, spacing, shape
Chickens sleep on a bar, not on the floor, and they will pile up and smother each other trying to reach the highest one if you only give them a single option. Allow eight to twelve inches of bar per bird — more in winter, because birds bunch together for warmth and you want the room available when they do.
Run the bar two to four feet off the ground. If you use several, stagger them like a ladder rather than stacking them directly above one another, or the birds on the lower bars get rained on all night.
Make the bar flat rather than round — a two-by-four laid on its wide face is the classic, and it lets a hen sit down over her own feet and cover them. Round dowels leave toes exposed, which matters in a cold snap.
Keep the roosts higher than the nesting boxes. If the boxes are the highest thing in the coop, the birds will sleep in them, and birds sleeping in a nest box means droppings in a nest box every morning.
Nesting boxes: fewer than you think
One box for every three or four hens is plenty, and this surprises people building their first coop. Hens do not want a box each. They want the box — and a flock of twelve will queue for the same one while three sit empty. Building eight boxes for eight hens is wasted material.
Twelve inches cubed suits standard breeds. Ten is enough for bantams, and a large breed appreciates fourteen. Mount them low, keep them darker than the rest of the coop, and add a lip at the front so the bedding stays where you put it.
Ventilation is not the same as a draught
This is the detail that does the most damage when it is misunderstood, particularly in winter.
Chickens handle cold far better than most people expect. What they handle badly is damp. A closed-up coop full of birds fills with moisture from breathing and droppings, and that moisture is what causes frostbitten combs and respiratory illness — not the temperature.
Aim for about one square foot of vent per ten square feet of floor, placed high, above roost height, so warm wet air leaves without blowing across the birds while they sleep. Ventilation up high is good. A draught at roost level is not. Sealing the coop tight for winter is the most common and most harmful mistake in backyard chicken keeping.
Predator-proofing, briefly
Space keeps the flock healthy. Hardware keeps it alive.
Use half-inch hardware cloth, never chicken wire — chicken wire keeps chickens in and stops nothing from getting in. A raccoon will tear through it, and a weasel will walk through the gaps. Bury the mesh eight to twelve inches or run an apron a foot out from the base, because almost everything that wants your birds digs.
Fit two-step latches on every door. Raccoons open simple hooks; they have hands and patience. And cover the run if you have hawks, which you do.
Sizing a real flock
Six standard hens, which is a common first flock, want 24 square feet of coop, 60 square feet of run, six feet of roost bar and two nesting boxes. Ten hens want 40 square feet of coop and 100 of run.
Build for more birds than you intend to keep. Nearly everyone adds to the flock in year two — it is such a reliable pattern that it has a name — and extending a coop is far more work than building it slightly larger once.
If you would rather not build, a coop with an attached walk-in run gets you the covered space and the predator hardware in one piece, which is the part that takes longest to do properly from scratch.