Build a hen roost from a 2x4 set on edge, so the 1-1/2 inch face is what the birds stand on, with the top corners rounded, the bar 20 inches off the floor, 10 inches of bar per hen and at least 7-7/8 inches clear of the wall. That is what our plan books draw, and it is cut from the same stock on every coop from the 4x6 up. The only things that change with the size of the coop are bar length, how many bars there are and how many legs hold them up.
The numbers below come from three of our plans: the 4x6 (3 to 4 hens), the 6x8 chicken coop (6 to 9) and the 8x12 walk-in (14 to 18). Each one lists a built bar length and a requirement, and they are not the same number.
Three roost builds, cut to the interior
| 4x6 coop | 6x8 chicken coop | 8x12 walk-in | |
|---|---|---|---|
| Hens | 3-4 | 6-9 | 14-18 |
| Roost bars | 2 at 25 in | 2 at 49 in | 3 at 73 in |
| Built bar length | 50 in | 98 in | 219 in |
| Inches per hen at full stock | 12.5 | 10.9 | 12.2 |
| Inches per hen at low end | 16.7 | 16.3 | 15.6 |
| Wall cleats (14 in 2x4) | 4 | 4 | 6 |
| Center legs (16-1/2 in 2x4) | 0 | 2 | 3 |
| Droppings board | 27 x 24 in | 51 x 24 in | 75 x 24 in |
| Board rails (2x2) | 2 at 27 in | 2 at 51 in | 2 at 75 in |
The plan’s requirement is 10 inches per hen, so a nine-bird flock needs 90 inches and the 6x8 builds 98. Every coop builds a little over, because bars come in whole pieces that fit the wall, and that spare length is what lets a hen move down the bar on a cold night. Penn State asks for 6 inches per bird and Oregon State 5 to 10, so all three sit at or above the generous end of what extension publishes.
Why on edge, and when to lay it flat
Our books say to use a bearing surface 1 to 2 inches across, because a thin dowel and a full 3-1/2 inch flat face both put pressure on the footpad. Oregon State’s coop guide says the same thing in its own terms: 1- to 2-inch square lumber with the top edges rounded off. Laid flat, a 2x4 presents 3-1/2 inches. Mounted on edge it presents 1-1/2, and you ease both top corners with a plane or a sander.
There is one exception and the books name it. In hard-freeze country some keepers lay the bar flat so a hen can settle her breast feathers over her toes. Frostbite there is a moisture problem as much as a cold one (University of Minnesota Extension, as cited on our insulated plan page), so a dry, well-vented coop does more for toes than a wider bar does. If you live where the floor of the coop freezes, decide that before you cut, because the bar orientation changes how many inches of bar fit the wall.
Height, spacing and the wall
Set the top of each bar 20 inches off the floor, 11-13/16 inches apart and at least 7-7/8 inches off the wall, and stagger them along the wall like stair treads so birds underneath are not under another hen. No bar sits above a nest box.
Extension ranges bracket those numbers, and they disagree with each other on height. Penn State says one foot apart and 18 to 24 inches above the floor. Oregon State says 2 feet off the floor with 10 inches between poles. The national poultry extension network’s perch article (poultry.extension.org) gives about 12 inches between perches, about 8 inches from a perch to the wall and the lowest perch about 3 feet up, so 20 inches is the low end of the published spread. Penn State also says never above 4 feet, and the reason is injury on the way down. Our plans keep all bars at one height, which also avoids the fight over who gets the top bar.
Legs, cleats and why a 2x4 sags
A 49-inch bar does not hold itself up. A roost bar is a 2x4 loaded on its narrow face, and no span table lists a 2x4 in that orientation. So the books put a center leg under any long bar: one on the 6x8 at 24-1/2 inches, one per bar on the 8x12 at 36-1/2 inches, and two per bar on the 10-foot-wide coops. No bar spans more than 48 inches between supports. The small coops, 4x4 and 4x6, get away with wall cleats alone at the two ends, 14-inch 2x4s screwed to the studs.
Under the bars goes the droppings board, a sheet of 3/4-inch plywood 24 inches deep and a little longer than the bars, riding on two 2x2 rails so it slides out. Sealed or lined, never wire: droppings stick to mesh. Pulling the board and scraping it is the cleaning routine in the cleaning guide.
Roost against nest height
Published rules pull in two directions. Penn State puts nests at least 2 feet off the ground and at least 4 feet from the roosts. Oregon State says do not set nest boxes lower than the roost poles. Our bars top out at 20 inches, and the 3-box nest bank floor sits 24 inches above the coop floor, so the nest is not lower than the roost by those numbers. The books handle the conflict by distance and not height: the nest bank goes at least 48 inches along the wall from the roost, never under a bar. If hens start sleeping in the boxes, the nesting box guide covers why, and the interior layout guide shows where the two sit in each coop.