When I first got my chickens my husband built a 10 x 12 coop for me. I had 27 chickens and 7 guineas. Over the past year we have gotten down to 16 chickens and 4 guineas. My guineas picked on the chickens during the winter months and I keep asking if we could add on to the coop. There are 4 more rafters the same size that we didn't use. We didn't have the money to pour cement to go under the addition this spring so I built a 4 x 8 coop that attaches to the same run out of left over building materials we had laying around. Planned for guinea use but using for youngsters right now. We now have 41 chickens (some still in the brooder) and still the same 4 guineas. My husband keeps saying I am the crazy chicken lady.... but this weekend he poured more cement so I have materials and a spot to double my coop size. Yeah!! The big coop will actually slide forward on the cement 5 foot and with the new 5 foot on the back lots more space. I'll be able to store everything inside not all over outside. I will have to decide how to change the interior layout to make use of all the space.