they need area to get away from the heat and cool off, and youd be better off with something with solid sides. My brooders are 4'x6'x2'h and hold up to 100 chicks
mine took exactly 2 4x8 sheets of ply. corners all done with 2x2's with 2x4 frame on the top.
Edit: Someone asked i explain this a little better so here is is. Sheet one is one single cut making a 2'x4' (end) and a 4'x6' (bottom) peice. Sheet #2 starts the same way but we split the 4x6 into 2...
Videos of the evolution of our brooders. Doing some more work on it this weekend, will post pics when the upgrades are done. lol
old brooder pool vs plywood brooder i built.
B&W vid i shot in the new brooder