10' x 12' coop size

The are s lot of factors that go into that, a non them....bantam or large fowl, climate, will there be a run or free range option, feed an Easter inside the run or out, what breeds are you considering, etc.

Generally a minimum of 4sf per large fowl bird inside and 10sf outside are recommended. ...not including the space occupied by feed, water, etc

 

Standard recommendation is for 3 square feet per bird of unused floor space. Much though depends on climate and opportunities to range (as well as the size of the birds).

So 10 x 12 would be 120 square feet, which would house 40 birds, but you'll need to subtract from that space taken up by feeders and waterers, posts that may be holding up your roosts, ditto for nesting boxes, etc.

If you live in a mild climate and the chickens will have access to range everyday, things will go easier.

If they need to be combined to a fenced in run that you create, plan on 10 square feet of space in the run per bird.

If you live someplace where weather will interfere with the chickens being willing to go outside, 3 square feet of space per chicken in the coop may be tight. Depends on the chickens. As an example, we get snow where I live, and my chickens were for the most part uninterested in going outside in the snow. So they remained inside the coop most of the winter; though they certainly had the option of going outside, they weren't interested.

All of these recommendations are generalities. You say "hens" so I suspect that means no roosters, which makes things a bit easier.

Different breeds, or strains within breeds, are more high-strung or more laid back.

Nonetheless, they will need space to be able to get along well. Otherwise there will be issues that will impact how much they lay, and could well lead to other health issues, or injuries if they fight a lot.

 

Oh, forgot to add above, you never hear anyone complaining that they've got too much space for their chickens.

You do hear of lots of problems for which the remedy is: provide more space. So the more space you can provide, the better.

 

So very very true!

 

I think it will be more a matter of how much ground is covered by that strange white stuff, and for how long, rather than how cold it gets. Mine were not willing to walk on the snow most of last winter. Some chickens do; think it's largely a matter of them deciding it's safe and not too uncomfortable.

Space to range is very helpful. Don't know your situation; I use 164 feet of electric poultry netting, when they aren't allowed to free range (I live in the country).

The mantra is always: more space = happier chickens.

Guessing you're after eggs. My guess is once they get going you'll get around 3 eggs for every 4 hens this winter; possibly better than that as Rhode Island's are supposed to be better layers than most. It takes them a while to get up to speed.

Figure out how many eggs you want, and build a coop and run larger than necessary to house that many chickens (as chicken math rules mean that you'll have more chickens than that next year).

 

Thinking about it, I'd adjust the number of eggs expected each day down a bit. Probably more like a 70% daily lay rate, so 7 eggs per day for every 10 hens, and it will take them several weeks to get up to that.