You’ll find people giving all kinds of magic numbers for how much room chickens need, all the way from 2 square feet with no run space to 10 square feet coop space only. I don’t know where any of them come from except the 2 SF. Commercial operations have shown you can crowd them that much under certain conditions. You need chickens specially bred to take confinement well, you manage the lights and feed, and maybe you trim their beaks so they can’t eat each other. Poop management is a big issue. We generally don’t treat our chickens that way or work that hard taking care of them.
How many chickens you can put in an area will depend on many different things: climate, flock make-up, individual chicken personalities, how you manage them, and many more. If you want you can follow the link in my signature for some of my thoughts. I don’t give you hard and fast magic square feet numbers, more of things to think about that might influence some of your decisions. In general I find the more I crowd them the more behavioral problems I have to deal with, the less flexibility I have to deal with issues, and the harder I have to work. A lot of this stuff is more about me than the chickens.
Chickens do not understand the concept of space in the coop versus space in the run. To them space is space if it is available when they need it. If you consider your run predator proof to the point that you are willing to leave the connecting door open all the time or if you commit to getting out there every day of the year early enough to open the door so that space is available to them when they are awake the coop space is less relevant. If you like to sleep in occasionally then coop space is more important.
I’m guessing you live in the wet part of Oregon so you might want to read this. The best time to fix a muddy run is when you are building it.
Pat’s Big Ol' Mud Page (fixing muddy runs):
Chickens are going to poop. When poop gets wet and stays wet it stinks. The more chickens you have in a small area the more poop is going to build up. Even with just a few chickens a wet run will carry a whiff, but lots of chickens in a small wet area, whoa boy, look out. You real enemy in this is wet so trying to keep it dry is of utmost importance.
Different substrates work, but conditions and how you manage them play a part. Sand drains really well as long as the water has a place to go. If you dig a hole in soil that does not drain all you have done is make a swimming pool filled with water and sand. If chickens are in the mix, poop is in there too. Sand is a great material as long as it is installed so the water will drain. Some people with a high chicken concentration on sand are out there daily scooping poop to lessen poop build-up. Sand is a great material for that. How hard do you want to work?
Just plain dirt will work as long as you can keep it dry or if it drains really well. But the chickens will dig holes in it for dust baths and those holes can hold water.
People use other materials; leaves, straw, wood chips, cotton seed hulls, and others. If it stays dry enough to not become a wet soggy mess this works great. It’s composting in the run. The chickens love scratching in it for creepy crawlies and will keep it turned for you. But if it becomes a wet soggy mess you may need to remove it and replace it. That sounds like work to me. Different things work for different people. There is no one substrate that works great for all of us. Even a few people that use sand occasionally remove and replace it because it doesn’t drain really well or the poop builds up to a ridiculous level.
There is no magic place for nests either. Some people put them on the floor, some put them high enough they don’t have to bend over to get the eggs. Do you have a bad back? I have nests high and low. Some chickens lay in the lower nests, some in the higher nests. At one time I only had lower nests. They all laid in those.
Since chickens like to spend the night on the highest thing available the main rule is to have the roosts noticeably higher than any place you don’t want them sleeping. That’s normally the nests. Position the nests for your convenience more than for your chickens. You are important too.
A secret to that to help keep them out of the nests is to be generous with roost space. Chickens can sometimes be aggressive on the roosts as they are all getting their favorite spots. If they can’t get away from these brutes some chickens get so tired of getting beat up that they leave the roosts and look for a safer place to sleep. If your nests are the next higher thing, it could be your nests.
There is no one way that is right for everyone in any of this. We are all unique and different things work for us. Good luck!