we simply made an extension on the back of the coop. Eventually the wall that divides them will come down and it'll be open to the rest of the coop.
this was just before we got them and before it was painted. It's now a sunny yellow with white trim. We have 13 chicks in here but only 8 are staying. I'm raising the others for friends who don't have room for a brooder. oh, and the heat lamp hung in the middle.