A large chicken coop, for 14 to 26 hens, needs 56 to 104 sq ft of bird floor and 112 to 260 sq ft of run, and we have five walk-in plans in that band: the 8x12 walk-in and its insulated twin (14-18 hens), the 10x10 (15-17), the 10x12 (18-22) and the 8x16 (19-26). Past 26 hens we don’t have a plan yet, and we’d rather say so than stretch the 8x16’s rating.
“Large” means different things to different people. For a backyard keeper it’s anything you walk into. For a homesteader selling eggs it starts at 20 birds. This page uses the plan data: a coop is on it if it carries at least 14 hens at our 4 sq ft per bird default, which sits above Oregon State’s 3 sq ft floor and well above Penn State’s 2.
The five large coops
| Plan | Nominal coop | Bird floor | Run | Rated | Nests | Roost bars built | Vent | Materials | Build | Feed room |
|---|---|---|---|---|---|---|---|---|---|---|
| 8x12 walk-in | 8x12 (96 sq ft) | 58 sq ft | 128 sq ft | 14-18 | 5 | 219 in | 5.1 | $4,250-$5,450 | 60-75 hrs | yes |
| 8x12 insulated | 8x12 (96) | 58 sq ft | 128 sq ft | 14-18 | 5 | 219 in | 5.1 | $5,500-$7,100 | 78-98 hrs | yes |
| 10x10 walk-in | 10x10 (100) | 84 sq ft | 120 sq ft | 15-17 | 5 | 194 in | 5.5 | $4,150-$5,350 | 60-78 hrs | no |
| 10x12 walk-in | 10x12 (120) | 74 sq ft | 160 sq ft | 18-22 | 6 | 291 in | 6.7 | $4,700-$6,000 | 75-95 hrs | yes |
| 8x16 walk-in | 8x16 (128) | 79 sq ft | 160 sq ft | 19-26 | 7 | 292 in | 7.0 | $4,950-$6,400 | 90-110 hrs | yes |
The gap between nominal and bird floor is where new builders get surprised. A 10x12 is 120 sq ft on paper and 74 sq ft where hens stand, because the feed room, the nest bank and the framing come out. The 10x10 has no feed room, which is why it has the most bird floor of the five (84 sq ft) despite being the second-smallest box. If you’d rather store feed in the garage and give the birds the space, the 10x10 is the best floor-per-dollar coop in the line: $4,150 for 84 sq ft, under $50 a square foot.
Floor per hen at the top of each rating
The rating is the honest number, so here’s each plan at its maximum: the 8x12 walk-in at 18 hens is 3.2 sq ft inside and 7.1 of run; the 10x10 at 17 is 4.9 and 7.1; the 10x12 at 22 is 3.4 and 7.3; the 8x16 at 26 is 3.0 and 6.2. Every one of those is at or above Oregon State’s 3 sq ft, and every one is under our own 4 at the ceiling. That’s deliberate. The top of the range is “it works,” the middle is “it’s comfortable.” Build the 8x16 for 20, not 26, and you’ll never think about floor again.
The run is the same story. At the top of each rating none of these hits 8 sq ft of run per bird. The 10x20 standalone run ($1,900-$2,450, 200 sq ft) is the usual fix for anyone running 20-plus birds that don’t free-range, bringing the 8x16’s outdoor space to 360 sq ft, almost 14 per hen at 26.
Roosts, nests and the feed room at scale
Roost space is 8 to 10 inches per bird (Virginia Tech’s figure). Our plans allow 10 per hen at the top of each rating and the cut lists build more: the 8x16’s four 73-inch bars are 292 inches, 11.2 per hen at 26. All five set the bars 20 inches off the floor and 11-13/16 inches apart over a removable droppings board you scrape standing up. That board is the thing that makes a 20-hen coop a five-minute morning instead of a twenty-minute one.
Nest boxes run one per four hens on the Oregon State rule. The 10x10 carries five for a 17-hen ceiling, which is slightly over; the 8x16 carries seven for 26, which is slightly under one per four. Hens share. Seven boxes for 26 layers works in practice, and the plan’s bank is 104 inches long with 12-inch-plus cells, over the 12 to 15 inch width Utah State specifies.
The feed room is 36 inches deep on the 8x12s and the 10x12 and 48 inches on the 8x16 (a 96 by 48 room you can turn around in), each behind a full-height partition with its own 30-inch outside door. Penn State wants 3 inches of feeder space per bird and one water nipple per 6 to 8, so at 22 hens that’s 66 inches of feeder and three nipples. Keeping bags, a scoop and a spare drinker outside the bird area is why those four plans give up floor to the room.
Cold-climate version
The 8x12 insulated coop is the 8x12 walk-in with insulated walls and ceiling, the same 58 sq ft and 128 sq ft run, at $1,250 to $1,650 more and 18 to 23 more hours. It’s the only insulated design in the line. If the birds will be shut in for weeks at a stretch, the extra floor the 10x10 offers matters less than the walls, and the insulation guide explains why vents stay open even then.
Permits: every coop here needs one
Not one of these clears the common 100 to 120 sq ft local trigger, and with runs attached all five pass the 200 sq ft that IRC R105.2 exempts: 8x12 plus 8x16 run is 224 sq ft, 10x10 plus 10x12 run is 220, 10x12 plus 10x16 run is 280, 8x16 plus 8x20 run is 288. Some towns count only the enclosed coop, in which case the 8x12 (96 sq ft) and 10x10 (100) might slip under a 100 or 120 line. Read the wording. The permit guide shows where to find it, and flock caps are a separate zoning rule that 20 birds will trip in most subdivisions.
Picking one
Fourteen to eighteen hens, cold winters: the 8x12 insulated. Fourteen to eighteen, mild: the 8x12 walk-in, our flagship. Fifteen to seventeen and you want the most floor for the money: the 10x10. Eighteen to twenty-two: the 10x12. Twenty to twenty-six, or any flock that might grow: the 8x16, the biggest coop we draw. For the twenty-hen decision in particular, the plans for 20 chickens page puts the 10x12 and 8x16 side by side.
The 8x12 walk-in, the insulated 8x12 and the 10x10 have their $4.99 plan books live on Etsy. The 10x12, the 8x16 and the 10x20 run don’t yet; their pages carry the full free spec and cut list and a “plan book coming” line.