In the Pacific Northwest, rain and mud are the enemy and cold is the minor one: raise the floor, drain the run, roof part of it, and keep the vents open in a damp 40-degree drizzle. Our best fit is the 6x8 walk-in shed coop, 7-10 hens for $2,900-$3,750, with a rain roof added over part of its run. Seattle allows up to eight fowl and Portland four, so size to the cap before you size to the yard.
The general-purpose climate guide lumps this region in with other mild climates. It deserves its own page, because the failure mode here is a run that never dries out.
What Oregon State says about coop basics
Oregon State University Extension’s publication EC 1644, “Living on the land: Backyard chicken coop design,” was written in Oregon and is the best starting point we found. It says to raise the coop at least a foot off the ground, use secure flooring, and put wire or netting over a mesh run. Fencing should be buried 6 inches to a foot. Ventilation removes ammonia, carbon dioxide and moisture, and passive openings are adequate for most backyard coops: build in as much as you can without creating drafts or letting predators in, and use fans only in warm, humid spells. Coops do not have to be insulated. The floor should slope so it drains when you hose it out, and the whole thing should be easy to clean weekly. For space it gives 3 sq ft per bird in the coop when there is a run.
None of that is rain engineering, so the rest of this page is our own design reasoning, labeled as such.
Raise it, then drain it
A raised floor is the first defense against damp. Oregon State’s minimum is one foot. The 6x8 walk-in’s floor is 12 inches off grade, exactly at that line. The plain 6x8 chicken coop sits at 20 inches, the highest floor in our small coops, and the 4x8 shed at 14. If your lot is flat and wet, take the extra height.
The run is where the mud lives. Our plans bed the run floor with 3 to 4 inches of coarse sand or 3/8-inch drain rock, and the 8x12 walk-in plan wants the run graded to fall away from the coop before the buried apron goes in, since you cannot regrade afterward. A French drain around the run is a site job our plans do not draw. If the only flat spot in your yard collects water, move the run or raise its surface. Our flooring guide covers surfaces and our run design guide covers layout.
Roof part of the run: ours is not a rain roof
The mesh roof on our standalone runs, the 6x8 and the 8x16, is a predator roof. The plan pages say so plainly: rain falls straight through it, and about a third of the roof carries 70-80% shade cloth, which is a summer measure. In a region with long wet seasons that leaves birds standing in a run that never dries.
So the Pacific Northwest build adds something we do not draw: a solid roof over part of the run, enough that hens have a dry floor to scratch on in a week of rain. Our run design guide gives the same remedy list for any low, unroofed run: raise it, slope it, drain it, roof part of it and bed it. Cover enough run that the birds can stay outdoors, which is the whole point, since a shut-in flock in a wet coop is where the damp problems start. Our roof guide covers what to put overhead.
We do not give roof overhang depth or gutter specs, because the plan data does not set them. Gutters off the run roof are a good idea, and a downspout that does not empty into the run is a better one.
Ventilation in a damp, mild winter
Mild cold, wet air. Michigan State Extension’s winter advice, a draft-free but well-ventilated coop, applies here at a gentler scale, and Oregon State says passive ventilation is enough. Our 6x8 walk-in has 3.3 sq ft of permanent vent along the top of the back wall plus three 18 by 23 inch windows screened inside with hardware cloth, so they can stay open on a drizzly night. Do not close the vent strip because it is raining.
The build: 6x8 walk-in, 6x10 run
| Item | Plan |
|---|---|
| Coop floor | 37 sq ft |
| Run | 60 sq ft |
| Hens | 7-10 |
| Floor height | 12 in |
| Vent | 3.3 sq ft permanent, three windows |
| Materials | $2,900-$3,750 |
| Build | 30-38 hrs, Intermediate |
The 6x8 walk-in shed coop has 72-inch walls and a 32 by 70 inch access panel. It is not insulated, which is correct for a climate where the problem is dampness, not cold. For a larger flock, pair a coop with the standalone 8x16 run, 128 sq ft for 16-25 hens, $1,300-$1,700. Its Etsy plan book is not published yet, but its free spec page is up.
Seattle and Portland rules
Rules differ sharply between the two big cities, and both cities’ own pages are short on coop placement.
Seattle’s Department of Construction and Inspections says it allows up to eight domestic fowl, with more allowed on lots over 10,000 sq ft, and no roosters, under SMC 23.42.052. Its page does not address coop setbacks or permits.
Portland’s page says up to four chickens, ducks, pigeons or similar fowl on a lot, six on lots of 10,000 sq ft or more, plus up to four under 12 weeks. No permit is required, but Title 13 standards apply, including structures at least 3 feet from side and rear lines and 10 feet from the front line. Large agricultural lots over 20,000 sq ft have no cap.
Both pages are agency summaries, not the code text. Read the code, and check your HOA. Rules elsewhere in Washington and Oregon vary by city and county, and we are not quoting any we did not read. Our permit guide shows how to find them.