Hi, welcome to the forum. Glad you found us.
Never be afraid to ask a question on here. The search function is challenging even for people very familiar with the forum so it is not easy to find what you are looking for. You are in a unique situation and your excellent post explained that very well. Many posts are more generic or may not specifically apply to you.
I think what you are considering is to have that 20' x 6' run available during the day. In that 6' x 6' area you label "coop" is still covered by wire and inside that you have a "hen house" of unknown size that will be totally enclosed with wood. The chickens would have access to both the coop and hen house areas at night with the roosts and access to the nests in the hen house. It's not what I'd call a normal concept but in your weather in the Bay area it could work if you make it predator proof.
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all enclosed at 6 feet tall.
You want to be able to stand up, whether in the coop or run. It hurts to bump your head. When I walk I kind of bounce up and down. Is that 6' tall the bottom of something you might bump into or the top?
Besides, any solid roof needs to slope so water runs off of it. You do not want that rainwater to run into your run because that will make it muddy. You do not want water to run off of the roof onto you as you are opening a door or maybe gathering eggs if you have outside access to your nests.
Do you think that is OK spacing for a flock of 8 max? I basically chose the sizes of each section for ease of math.
The overall size is fabulous for eight chickens. One huge consideration is your comfort and convenience. You need room to work in there. I don't believe in magic numbers for much of anything as far as chickens go. You can follow the link in my signature below to see why that pertains to space. Think as much in terms of you as you do of chickens.
What I want to know is how much space the "hen house" itself should be in a 6' x 6' square foot space. I will keep the waterer and feeder outside the 'hen house' itself.
What you need in the enclosed "henhouse" section is a roost. You are feeding outside. For eight hens you probably want something close to eight feet of roost space. That can be one roost 8' long, two 4' roosts, or even an L-shaped roost 6' and 2', 5' x 3', or something like that. I think your 6' x 6' area is too small to do that and give you room to work in that end. I'd consider making the run area shorter so you can make the coop area bigger. That may mean extra costs for more hardware cloth to make it predator safe and maybe some more wood to build that enclosed shelter. Or can you move the people door to the end? I see you have a nest hanging outside that area, probably for outside collection. Could you move that hen house to the far side and keep the nest inside where you would need to enter the coop area to gather eggs? I'm having trouble coming up with enough sheltered roosting area and still give you decent access in a 6x6.
I have seen the figure for square footage requirements per hen in the hen house, but how does one figure height into those calculations?
As I said I don't believe in those kinds of magic numbers. Chickens do not think in concepts of coop space versus run space. If they need space they don't care where it is as long as they have it.
As for vertical space, my method is to determine where the coop floor is, including any bedding depth. Then position your nests. Some people like nests on the coop floor. Some prefer them up higher, maybe so they don't have to bend over to gather eggs if they have a bad back. If kids are going to be collecting eggs you might want the nests fairly low. Again, think of you, the chickens can adjust. Next position the roosts higher than anything you don't want them roosting on at night. That usually means your nests but might mean something else. In colder climates I then would want ventilation openings above their heads when they are on the roosts so any breezes flow over their heads instead of hitting them. In the Bay area that is not as important.
I'd also want the roosts to be as low as I could reasonably make them. The higher the roosts the more clear space they need below to land in. You don't want them banging into nests, walls, or such on the way down. In what I think is your configuration I'd consider a sloped roof to keep rain off of them and four walls hanging down to keep rain from blowing on them or in the nests but leave the bottom open.
For 8 hens you need two nests.
I would like to use this project as an opportunity to learn some woodworking/construction skills, but to be honest, am not at all handy *right* now. For me, time is not the issue, but skill and cost is.
Most building materials come in standard 4' or 8' dimensions. If you can factor those into your design you can usually reduce the number of cuts and waste. A 6' dimension isn't horrible, you can often use the cut-offs for nests or something else. Cutting a 2x4 isn't that hard but cutting an 8' long piece of plywood requires some thought if you want a straight edge.
Another issue can be tools. If you are not skilled in construction you may not have many tools. The right tool makes a lot of difference, saws especially, but can be kind of expensive to buy. I suggest you screw things together instead of a hammer and nails. Mistakes and changes are a lot easier to handle if you screw things together. If what you are building is kind of flimsy it can be hard to even drive a nail.
You can manage this. When my boys were 10 and 12 I had them build a small shed for me to house the lawn mower and such. Of course I supervised but they did the work and read the plans. After that when they were helping on Boy Scout projects they amazed their friends with how well they could handle a hammer with one hand.
You can get books on how to construct at your local library, look for shed how-to books. Home Depot or Lowe's often have books on that.
If you can find a building you can avoid a lot of this. Prefab sheds can be expensive but aren't that hard to erect or convert into a coop. You will probably need a foundation. If you can find something on Craigslist you might save money. You might ask at a construction site if they have waste lumber, they often use stuff as a construction aid and the throw it away.
Good luck with it, it is a project. And once again,
