You are certainly in the right place to get opinions. Just remember that’s what most of this is, personal opinion and personal preference. Some features I find useless others really love. Some I really like others don’t care for. We are all unique with different goals, climates, management techniques, set-ups, and just so many other things that there cannot be any one answer right for everyone. To me that’s one of the hardest things about this forum, you get so many different opinions it’s challenging to decide which actually apply to your situation.
From your screen name I could assume you are probably in a relatively warm climate, but that’s only a guess. Your climate can influence a lot of this. Extreme heat is usually more dangerous than cold, but you may have to take both into account. Even if you are south of the border you may be at a high enough elevation that you have to consider cold. I just don’t like to assume.
First some homework. If you look at the top of this design construction section, there are some stickies that have a lot of good information. You might follow the link in my signature. I don’t give hard and fast numbers, more of things to consider. And I’ll give you these links. The best time to fix a muddy run is during the design phase. The other may or may not be that helpful.
Pat’s Big Ol' Ventilation Page
https://www.backyardchickens.com/web/viewblog.php?id=1642-VENTILATION
Pat’s Big Ol' Mud Page (fixing muddy runs):
https://www.backyardchickens.com/web/viewblog.php?id=1642-fix-a-muddy-run
In my opinion the essentials for a coop for 20 hens other than adequate room are nests, roosts, protection from predators, and protection from the environment. You need a way for them to get from the coop to the run and back. Some people use a human door but I like a smaller “pop” door chicken size. A human-sized door can let in a lot of weather.
How you manage them and your goals makes a lot of difference in what else may be handy. You don’t mention a rooster, just hens, so does that mean you will not have a broody hen hatch or raise chicks with the flock? How do you plan to get replacement chickens, hatch them, buy baby chicks and raise them, or buy older pullets? When you integrate you need more room.
I like to be able to access the coop through a human door without going through the run. I like a human door between the coop and run for different reasons. Where I store food and have water is next to the coop and I feed and water both in the coop and run so that door is convenient. It’s highly beneficial to me when I’m doing something with the chickens to be able to go directly from one to another. But there might be times a door or gate directly into the run comes in handy, especially one you can get a wheelbarrow through.
I built some nests so I could gather eggs from outside but never use that feature. Some people love them and with tiny coops they are essential. My personal preference is to go inside the coop to gather eggs, I’ve found dead and injured chickens, snakes, and a possum in my coop that I would have missed gathering eggs from the outside. I like to know what is going on inside my coop.
With 20 hens you need a walk-in coop. You need to be able to access everything inside the coop. You may need to do maintenance, make changes, collect eggs not laid in the nest, or recover a sick or dead hen. If you want to check or treat your hens, the easiest way to catch them is to pick them off the roost at night when it’s dark. I just could not envision managing a coop with 20 hens that I could not walk into.
With 20 hens I’d suggest five nests. That should be plenty for you. I made my nests 16” x 16” to match my studs, that made framing easy plus if you cut a 4’ or 8’ piece of plywood or lumber into 16” sections you don’t have waste. You don’t with 12” either, but my bigger nests can handle more hens.
I’ll show a photo of mine so I can talk about the next things. There are plenty of other ways to do any of this, I’m not saying you have to do this my way, but it’s how I did it.
I really like having a coop big enough so I have room to do things inside. I built this 3’ x 6’ brooder in there and use the top as my droppings board. As you can see it did not go all the way so I got a couple of plastic bins and set them on the floor. I scrape the top of the brooder into the bins and just carry them outside to my compost.
People do use roll-out trays to collect droppings, usually in pretty small coops. They can work. I personally have trouble imagining a roll-out tray big enough to handle 20 chickens that is not so heavy it’s really hard to work, plus it can possibly bind. If you do go with that roll-out tray idea, I suggest several smaller trays, not one big one.
When I built this brooder I put ½” hardware cloth on the floor. I elevated it enough I can out more bins under it to catch poop. In colder weather when I’m brooding chicks I put something on a part of the floor to help hold in heat, in summer it is not an issue. Since it has a wire floor, it works as a broody buster when It’s empty. I’ve isolated chickens in here too, injured or for some other reason. I let my broody hens hatch with the flock, I don’t isolate them, but it might work for that too, you would need to add a nest and maybe put something on the floor to block airflow underneath.
Not all wire is equal. Some has sharp nubs that can chew up a chicken’s feet. Due to the manufacturing process, these nubs, if they are there at all, should all be on one side. Before you install it as a floor, carefully rub it with your hand to see if that side has any sharp nubs.
That’s enough for now. Welcome to the experience.
