Here is one I'm looking at. I'd use the bottom part. It's 50" w x 20" deep and can be made into 2 levels (approx 7 sq ft per level, minus some for a ramp).
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Here's another that looks deceptively small, but it's 44" w x 24" d, so similar sq ft.
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Yes, I've thought about the chick with the leg deformity. I'm assuming it will stay on the lower level with the coop/nest box. So maybe 2 levels would be better.
Problem is we just don't have the room for a large footprint. We have a very small house. Eventually, I hope to have them outside in their own coop on our covered deck.
2 levels might make more sense. If she'll stay on the bottom, probably best to keep her friend close by, no farther than the top level. Otherwise she may try to find her and go up the ramp, or something like that. Otherwise, I like it, its a good idea.
Thoughts. If you can guesstimate that each level is about 7 sq ft, thats not enough room for even 1 chicken. If there are two levels thats better, but assuming they will stick together most the the time, I'm not even sure that the Polish without leg issues will go to the upper level much by itself. Surely she will sometimes, but for the most part I bet she'll hang out with her buddy. With that in mind, 7 sq. ft is not nearly enough space for two chickens. Even if the other did go to the upper level often, 14 sq. ft isn't nearly enough room for 2 chickens. Of course, these guys are disabled, so you have to make do with what you have. But, there's definitely some hoops to jump.
Also, a narrow space, is no good. You can always use space better when its square, rather than long and skinny. For bullying reasons mostly. Wether or not there will be much bullying going on with these disabled babies is questionable, but definitely something to think about.
Hmm, I feel ya with the small house, ours is absolutely tiny. I still think that levels probably isn't the best. Just because the leg issues chick wont be able to use the other levels, and or the reasons listed above.
I think that a large open space, such as a dog X-pen, or similar is a better idea. Though the small house makes that design difficult. This is when you have to get creative. I did a lot of reading on this when I had to fit my bun, Aspen into the house when I had her.
Is there a table or similar you could put the X-pen under? Using the space under objects is often a good way to use unusable space, and to not take up any room in the house. Think outside the box. Any unused space, or shareable space you have? Loft beds, or bunk bets without the bottom bunk work great for this.
Alternatively, knowing this is temporary anyway, do you have a garage or shed you could put them in? That would likely, A) Be way better for you. Chickens are dusty, and smelly, and not the easiest to fit into a household. As we both probably know. B) Be better for them. More space, more access to outdoor climate, etc.