The top of the line, and what 26 hens actually means
This is the biggest coop we publish. Nothing above it, so if you’re here, you’re either sure you want a big flock or you’re shopping for headroom to grow.
Design for about twenty. At 19 hens each bird gets 4.2 square feet of coop floor, just past the 3 to 4 square feet per bird that Oregon State and Virginia Tech publish for a coop with a run. At 26 it’s 3.0 each, the floor of that range with nothing to spare.
The run tells the same story. It’s 8 by 20 feet, 160 square feet, which gives 8.4 square feet a bird at nineteen, inside the 8 to 10 extension services recommend. At twenty-six it drops to 6.2. That’s a flock that needs to free-range some part of most days, or needs a second run added later.
The fixed gear is sized for 26. 260 inches of roost is 10 inches a bird at full capacity, and seven nest boxes is one per 3.7 hens. Run your own flock numbers through the coop size calculator before you commit to the top figure.
The lowest cost per hen in the walk-in family
| Coop | Bird floor | Run | Hens | Materials | Per hen at max |
|---|---|---|---|---|---|
| 8x12 walk-in | 58 sq ft | 128 sq ft | 14–18 | $4,250–$5,450 | $236–$303 |
| 10x10 walk-in | 84 sq ft | 120 sq ft | 15–17 | $4,150–$5,350 | $244–$315 |
| 10x12 walk-in | 74 sq ft | 160 sq ft | 18–22 | $4,700–$6,000 | $214–$273 |
| 8x16 walk-in (this one) | 79 sq ft | 160 sq ft | 19–26 | $4,950–$6,400 | $190–$246 |
Divide materials by the top of each capacity range and this design comes out cheapest, because the last four hens cost very little. Going from the 10x12 to this one is $250 to $400 for four more birds.
That column flatters it, though. It only works at 26, and 26 is the tight end of this coop. At 19 hens the per-bird figure is $261 to $337, no better than the smaller designs. The savings are real only if you actually fill it.
36 feet long is the real site question
Coop and run together run 432 inches, 36 feet, on an 8-foot width. That’s 8 feet longer than the 8x12 or 10x12 walk-ins, and it’s the dimension that decides whether this fits your yard.
It needs one straight run of reasonably even ground, and that rules out the corner of most yards. Think about access too: you’ll be carrying 16-foot posts and 22-foot 2x4s into the site, so a gate or gap wide enough to swing long stock through saves an afternoon of frustration. Walk the site with a tape before you order anything, and check that the far end of the run clears your setback line.
Length also makes grade matter more. The plan sets every pier block, 16 of them, to one string line, and all heights are measured from the top of the block. On a yard that falls a few inches over 36 feet, the downhill blocks end up well proud of the dirt. Then the run surface needs to fall away from the coop so it drains. The run design guide covers why a run that ponds is where flock health problems start.
The only feed room here you can turn around in
The 8x12 and 10x12 walk-ins both close off a room 36 inches deep. This one is 48 inches: a 96 by 48 inch room, 32 square feet, behind a full-height stud wall with its own 30-inch outside door.
That extra foot changes what the room is for. At three feet it’s a corridor with bins along the back. At four you can stand inside with the door shut, keep a bedding bale on the floor and still reach the shelf behind it. It’s the closest thing to a real potting-shed room in the line.
As with the smaller feed rooms, it isn’t bird space and the capacity numbers already leave it out. Stored feed draws rodents, which is why the partition runs all the way up to the roof rather than stopping at the low wall.
The build is two weeks and a lot of fasteners
This is the longest build we publish, longer even than the insulated 8x12: 90 to 110 hours, twelve to fourteen days, 36 material line items across 19 steps, in a 42-page plan book.
The material list shows where the hours go. 252 feet of quarter-inch hardware cloth, fastened through 1,008 fender washers. 360 roof screws on nine corrugated panels. 88 eight-foot 2x4s before you count the longer stock. None of it is hard, but all of it is repetitive, and the repetitive work is where people get sloppy by the third day.
Quarter-inch cloth is the spec because a least weasel gets through half-inch, per University of Kentucky Extension ID-245. Across 252 feet it’s tempting to save money on half-inch. Don’t. See the predator-proofing guide for why the buried apron matters as much as the mesh size.
128 square feet clears some permit lines and not others
The building itself is 8 by 16, 128 square feet. With the run, the whole structure covers about 288 square feet of ground.
IRC R105.2 exempts detached accessory structures up to 200 square feet. Towns that tighten the exemption commonly land on 100, 120 or 144. This building is over the first two and under the third. Of all the walk-ins, this is the one where two neighboring towns can give you opposite answers. The permit guide covers what to ask, and remember setbacks are a separate zoning check.
A 16-foot building with three windows
Twenty-six birds put a lot of heat and moisture into a building, and the design handles it with 7.0 square feet of permanent vent, the most of any walk-in here. There are three windows, the same count as the 8x12, spread over a building four feet longer.
In a hot climate that’s the thing to plan around. Keep the windows open and screened on summer nights, give the run real shade, and orient the long wall to catch whatever breeze your site gets. In a cold one, leave the vents open all winter; moisture, not cold, is what frostbites combs. The ventilation guide covers both.
What this design deliberately does not do
There’s no bigger size to grow into. Past 26 hens you’re looking at a second building, not a longer one.
It isn’t insulated and it isn’t a first project. It’s framed to published span tables rather than to a stamped structural design, it’s rated Advanced, and it takes two weeks. If the flock you actually have is closer to a dozen, the 8x10 walk-in does that job for a lot less money and a lot less weekend.