How much room do chickens need?

I purchased some baby chicks earlier this year to eat the slugs in my yard and provide eggs. Of course, now that they are old enough to be outside instead of being under a heat lamp in a box in the bathtub, the weather has gotten to hot for slugs to survive.

I bought materials for a small coop and my neighbors built it for me. It is simply a wooden frame with a hinged top lid, and plastic chicken netting stapled to the wood. I put an old plastic crate in there which the chickens roost on at night. I also cover the top with a tarp to provide shade, and cover entire coop when I put on the sprinklers.

The coop is about 8 square feet. My four juvenile chickens seem to like it just fine. This size might work well for someone with limited space. I would like a much larger area. The chickens love running around, and I'd like more space so they are not running in poop. I would also like to be able to walk in and visit the chickens. Letting them run around my yard is not an option because I am afraid they might get under the gate or up in a bush or tree. If they climb too high they might make it into a neighbor's yard where they will quickly become a snack for one of the 10 dogs in the yards adjacent to mine.

I decided to build a bigger coop. Maybe they do not NEED the extra space. I know they will enjoy it, and so will I. I found a set of coop plans on ebay. When finished, it will be about the size of a bedroom. I will be able to visit my chickens and hand feed them. They will be able to run around and flap their wings. The coop will have an enclosed area for roosting and egg laying.

I am very excited about this new coop. I was thinking about the chickens when I decided I would build them a new home. Now I realize that I will get a lot of enjoyment out of it as well. I plan on placing it where I will have a garden next year. This year, I can plant some things next to the coop for the chickens to eat as it grows through the fence. I was even thinking about placing straw bales next to the coop and planting in those. That way the chickens can eat both the plants and the bugs, and the straw will decompose into nice soil.

So how much room do chickens need? Some farms keep them in cages so small they can't walk. My chickens will get room to try to fly. It may not be complete freedom, but they will be safe and they will even get some quality human attention. They will be part of the family.

P.S. my dog likes to lay near their current coop. I will use the smaller coop for day use in new areas where there are plants and bugs for the chickens to discover.