Need advice on coop size

[Pyxis]

Okay guys, I'm looking to get a bigger coop for my birds, since my population ballooned up this year due to irresponsible neighbors *grumble grumble* Anyway, here's the question: I currently have a flock of thirteen birds, and I'm going to add four or five more, getting me up to 18 possibly. Three are bantams, and two of the added birds would be as well. One is a Red Pyle OEGB, and if you're not familiar with how small they are, here she is:

She's not getting any bigger

Anyway, someone is selling an AWESOME coop on craiglist near me. It's got a 6x8 walk in fully enclosed covered run, and an upstairs 4x6 roosting area with several roosts. There's room for the birds to get underneath the upstairs area and be sheltered during bad weather. I free range, so they'd only be confined to the coop at night and during bad snowstorms. Would this coop be big enough for them?

Edited to add that it has built in nest boxes with outside access and is set up for electricity for heated water during the winter. It even has a little built in ceramic heater to take the edge off the cold if it gets really bad. Seriously, I love this coop. I hope you guys think it's big enough! If not, I may just have to get it anyway and expand a bit

 

[Darklingstorm]

Is the roosting area open to the rest of the run? or enclosed like a coop?

If it is enclosed then 4x6 (24 sq feet) is not enough room.

according your message you have 13 heavy breed birds, each bird requires at minimum 3 sq. feet for a total of 39 sq feet add to that 5 bantam chickens that require a minimum of 2 sq feet each a total of 10 sq feet.

So your minimum space required for healthy happy birds would be 49 square feet of coop space (remember even though you free range there maybe a time that all chickens would have to stay inside for long periods of time).

 

[Time-Out]

In NY, you'll be looking at them wanting to be indoors a lot during Winter.

You could get that coop for the bantams as the bigger ones are likely to pick on them, but you'll certainly want something MUCH bigger. I'd look for more of a 90sqft coop if you're wanting to house them all together, just so the little'uns can get away if necessary.

 

[Pyxis]

Alrighty. Oh, my little guys don't get picked on. They're fairly high up in the pecking order. I've decided to add just four more birds, so the total will be 17, 5 of whom will be bantams. I'm thinking I might just bump out the roost area to give each bird at least 3 square feet of space. The roost opens into the run, so they'll have access to it at all times. During the winter, I was thinking of closing most of the run in with clear plastic to keep the wind out, so they can have some "outside" time too. Or, I can start from scratch and build a new coop, but I feel like that would cost much more than just modifying this one. Not sure on that though - what do you all think?

 

[Jubilee1111]

If the price is right, I would go for it. You can always build on, or just add another smallish-sized coop when fall comes.

I like to think of it as a cottage community. They enjoy common outdoor areas but can go home for privacy and comfort at night or for nesting