If your chickens are going to free range during the day, you really don't need a huge shed. The recommended space is 4 sq. ft/bird (heavy breed), but if they are going to be outside for most of the day, you can get by on less. The problem will be wintertime - if they are all confined to the coop because of weather, if the area isn't big enough pecking, feather pulling etc. might set in if they don't have enough space.
The basic structure needs to be secure, draught free and easy to maintain. If you are good at basic carpentry, you could build one yourself - I did!
My corners aren't 90 deg. joints are a bit wonky, but it serves it's purpose! There are several books with coop designs, also several good looking coops here under the learning tab. Self built would be cheaper, especially if you can get 'donated' wood. Just make sure it's chemical free,
The basic structure needs to be secure, draught free and easy to maintain. If you are good at basic carpentry, you could build one yourself - I did!
