If you plan to have a quarantine area, it will have to be away from your 12 X 30 barn to be effective. Some disease organisms travel on dust particles in the air, not to mention on your boots, clothes, etc. I like a clean walkway either down the middle like mine (pens on both sides, doors on both ends), or in your case on one side. Yes, it eats into pen space, but well worth it in my estimation. That way you can reach all your pens for feeding and watering without actually walking into them if designed properly. Even the nests can be placed within reach of an opening. Don\'t forget ease of cleaning; the less cracks, crevices, and obstacles the less time it takes to clean. Movable hanging feeders and even waterers can be handy.