Our shed-roof chicken coops are pitched 3:12 and covered in corrugated metal screwed to a 3/4-inch plywood deck, which is the shallowest slope exposed-fastener panel makers publish. The rafters are 2x6 on 24-inch centers up to a 96-inch-wide coop and 2x8 at 120 inches. The gable coops are a steeper 12:12 with 2x4 rafters and a tie across every pair. The three A-frames are the exception and take roll roofing.
That is the real picture across our plans, and it differs from what most coop-roof pages tell you. Here is what each number is and where it comes from.
What each of our roofs is
| Design family | Roof | Pitch | Rafters | Covering |
|---|---|---|---|---|
| 4x4, 4x6, 6x8 chicken coop, 8x12 chicken coop | Gable, ridge board | 12:12 | 2x4, a tie per pair | Metal on 3/4 in ply |
| 4x8 shed, 6x8 to 8x16 walk-ins and variants | Shed (one slope) | 3:12 | 2x6 at 24 in | Metal on 3/4 in ply |
| 10x10, 10x12 walk-ins | Shed | 3:12 | 2x8 at 24 in | Metal on 3/4 in ply |
| 4x8 lean-to | Shed on a ledger | 3:12 (12 in over 48 in) | 2x6 on a ledger, joist hangers | Metal on 3/4 in ply |
| A-frames (three) | 60-degree peak | steep | 2x2 or 2x4 | Roll roofing |
The 8x12 walk-in shows the detail. Seven 2x6 rafters, each 110-15/16 in with a 12-in tail, birdsmouthed on both ends. Five sheets of 3/4-in plywood laid with the 8-ft side up the slope so every seam lands on a rafter. Seven corrugated panels, 26 in wide with 24 in of coverage and 10 ft long, each one piece from eave to ridge so there is no lap partway up the slope, held by 280 neoprene-washer screws. That is 40 screws a panel.
Why 3:12
Exposed-fastener metal has a published floor. Gibraltar’s corrugated sheet says the panel is recommended for roof slopes of 3:12 or greater, and HPM’s installation guide says exposed-fastened panels belong on a minimum slope of 3:12 or greater and to inquire below that. Our shed roofs sit right on that line: 24 in of fall across the 96-in width of the 8x12, 18 in across 72 in on the 6x8, 12 in across 48 in on the 4x8.
Right at the minimum means there is no margin, so the laps matter: a full corrugation of overlap, rubber-gasketed screws through the ridges of the corrugation and not the valleys, and work from the eave up. If you want a shallower slope, buy a different panel and ask the maker for its number; we do not draw one.
Shingles need more pitch. Our materials guide gives asphalt shingles a 4:12 minimum, or 2:12 with doubled underlayment, which is steeper than a 3:12 shed coop, so a shingled version of our sheds is not a straight swap. A-frame coops use roll roofing, and the reason is the ridge: nobody sells a cap for a 60-degree peak.
Rafter sizes and why they change
A single-slope roof has no ridge, no opposing pair and no outward thrust, so it needs no tie; the load lands straight down on the two side walls. That is why it is the simplest roof in our line to frame. The rafter spans the full width in one piece, and the plans size it from the 2021 IRC table: for Spruce-Pine-Fir No. 2 at 24 in on center, 30 psf ground snow and 10 psf dead load, a 2x6 spans 117 in and a 2x8 spans 148 in, measured horizontally.
Run those against our widths and the pattern appears. A 96-in coop uses 82% of a 2x6’s 117 in. A 120-in coop would overrun it by 3 in, so the 10x10 and 10x12 go to 2x8 at 81% of 148. Span is horizontal, so the slope costs you nothing; only the width counts. We have not re-checked the table text this session, and the 30 psf is the plan’s assumption, so look up your own snow load before you copy it. The cold climate guide is where that lives for snow country.
Gables flip the logic. At 12:12 every rafter is a 45-degree plumb cut, and the ridge sits 24 in above the plate on the 4x6, 36 on the 6x8 chicken coop and 48 on the 8x12 chicken coop. A pitched roof pushes the walls outward, so each opposing pair gets a 2x4 tie at top-plate level, per IRC R802.3. The ties are also what the droppings board hangs from. Rafter framing in general is covered in the framing guide.
Metal, shingles, roll or polycarbonate
These are the ranges in our materials guide, not new quotes: corrugated metal at $2.50 to $4.00 a sq ft, 3-tab shingles at $1.50 to $2.50, polycarbonate at $2.50 to $5.00. For a standard 4x8 coop the guide totals metal at $60 to $120, shingles at $80 to $160 with the plywood and underlayment, polycarbonate at $100 to $200 and roll roofing at $20 to $60. Shingles always need continuous plywood and our plans deck in plywood anyway, so the gap closes. Polycarbonate brings light over a run but the guide says to cap it at a third to half the area. Treat all of those as the site’s numbers, and price your own.
Overhang and the vent under it
Our tails run 6 in on the 4x8 sheds, 9 in on the 6x8 and 12 in on the 8x12. The materials guide recommends 6 in as a minimum, 12 in for temperate climates and 24 to 36 in in desert heat to shade the wall. Put the tail where the vent is: the 8x12’s vent strip is the top 5-1/2 in of the high back wall, and the overhang is what keeps rain out of it. In Arizona the overhang is the cheapest shade you can add, and it is a modification to our plans, not something they draw.
Metal condenses on its underside when warm, wet air reaches it. The fix is air: never seal the vent. The 8x12 insulated coop shows the arithmetic, with a 3-1/2 in batt in a 5-1/2 in rafter bay so 2 in of channel stays open above it, which is twice the 1 in the plan cites from IRC R806.3.
Roofing a run, with an 8x8 example
Our attached and standalone runs are roofed in 1/4-in hardware cloth, not solid panels. If you want metal over one, the roof is a shed roof with the same three rules: 3:12 or more, purlins no more than 24 in apart per the materials guide, panels 24 in of coverage. An 8x8 run with a 3:12 slope has 24 in of fall; the 64 sq ft takes four 10-ft panels across the 8-ft width, five purlins along the 8-ft length, and at our 40 screws per panel about 160 screws. That is our arithmetic for an adaptation, not a drawn plan. The 8x8 walk-in plan is the coop that run would sit beside.