NewHomesteader - I know the feeling. I was hoping to get the frame and floor for the coop done this weekend, but the humidity from last nights rain made me a little concrete shy. We did however, get the brooder box ready. It's roughly 37 inches by 34 inches rectangle and 2 feet high. The odd dimensions are because we recycled some kind of pallet (which I love cause it had these big blue 'feet' on them to keep it off the ground!).
Anyway, it's been in the upper 60s most of the day and according to my thermometer, the brooder space under the lamp is running about 90 degrees. The brooder is out in the garage and we had the big bay door open most of the day. We'll probably be keeping the door open a LOT out there for ventilation once we get the 'lid' on the brooder (probably next week I'll get that done).
I am a little worried about temperature regulation. As we all know, mother nature doesn't know if its summer or winter! I don't want them to roast on a 85 degree day but many 70 degree days like today and I'll be worried if they are warm enough.
I'll post pictures of my box tommorrow. It's nothing special, just 4 walls and a floor.