The brooder is done!!!!
I used all scrap lumber for this (mostly the slats from a queen sized slat bed and a table I found in the recyling center). I used all hardware cloth for the sides and have cardboard over them now to keep it from being too drafty. It is 15 square feet (3x5) and is currently residing in our master bath, which, conveniently, is gutted for a remodel right now.It is screwed together with corner braces so that it can be disassembled and stored. I didn't sheath the floor, instead I have a full size heavyduty cardboard panel over the slats so that I can just change it out when it gets gross. I am considering creating a separation screen.
The floor:

The sides (I cut those little nubs off on top):

Completed from the end:

From the top:

The babies came!!!