Unfortunately, that is what I am afraid of. LOL. At this point...planning on 10 x 20. I am building a serama coop. It will have individual pens inside of it to house them.
I'm crap at math but if you try to keep all of your dimensions equal to, or multiples of standard wood sizes you'll be a MUCH happier camper. Also, depending on your design, if you can build it in sections and then assemble those sections into one you'll be an even happier camper.
We were so close to being semi-neighbors. Winthrop was on our list of locations but we ended up in Brinnon instead.