I stumbled across this the other day http://www.kingcoops.com/coopdesigns.html It has lots of good ideas with pictures, my favorite design is the " Cluckers Palace " it would be a sweet house for a few of our spoiled bantams :)

Most coops have slant roof, and be sure to have a bank of windows facing south for maximum light. You're going to love having the concrete pad when it comes time to muck it out. I have a twenty by forty coop on a concrete pad, and I appreciate how much easier it makes to do the scraping and also it's easily hosed off afterward. The structure was built as a chicken shed so I didn't have much modifying to do when started our flock up. We have working windows and two sides with wire mesh to them when the windows are open. Ventilation is very important to poultry so all windows are operable. We have a small drop door to their exercise yard and that is completely enclosed with fencing, even overhead, for protection from predators. And also a human sized door for us. LOL. It should be large enough so you can easily move feed bags in and out and also wheel barrows for when you muck poop.

All the walls where windows are located have roosts to them, and the other two walls have metal laying boxes twelve per unit. I had a hundred hens at one time and twenty four boxes were sufficient, so twelve should be for thirty hens. You may want to fence off a small section for quarantining injured fowl because there will be times when that happens and the other birds will attack an injured bird and peck at it until it dies. This could also be used as a safe spot for brooding hens.

Lots of great pictures over on the backyardchickens.com. They have a forum that is huge.

I made mine!! This has proven to be predator-proof and low maintenance. Super happy with the outdoor area - we can go away for a weekend and the "the girls" are quite happy. Check out pics here! https://wineandcountrylife.com/raising-chickens/