The day old chicks we were raising outgrew their cage in the house after about 4 weeks. They were ready to move outside to the barn. They didn’t need the heat lamp any more and were ready for more space and fresher air (the house needed to be aired out by that point as well!).
I used an outdoor pet exercise pen and covered the outside with chicken wire to make sure the chicks couldn’t squeeze out between the bars. I added a wooden crate and a cement block inside to give them something to climb and roost on. The floor is covered with pine shavings to help maintain cleanliness and provide the chicks with something to kick through. The roof over the pen was just a scrap of wood from the barn to prevent them from flying out and any other chickens from getting in.
Click through for a video and more photos of the baby chicks.