Deb,
The measurements are 4 feet long, 2 feet wide, 2 feet high. I\'m brooding about 30 birds (down from the 40 I projected). You don\'t want anything much larger than this, because it becomes bulky and heavy to move. Beyond 30 - 40 birds, just build a second unit.
You can get pieces of 4 x 8 3/8\" plywood from the local big box (Home Depot or Lowes) usually cut down into \"handy boards.\" I used three 4 x 2 sheets and two 2 x 2s. I used some 1 x 2 strips to join the pieces, because there is no other way to join plywood, especially plywood this thin. I didn\'t want to get involved with mortise and tenon or anything fancy for a brooder box. The beauty of this is that the only cutting you\'ll have to do is the 1 x 2 strips. The rest is screwing with the cordless drill. I used 1\" x No. 8 screws. I prefer the square heads to flat and philips -- the square heads don\'t slip. Construction can be done in about 90 minutes to two hours at a liesurely pace -- I did it in an hour, but I was rushing some.
Get a piece of 2 x 4 that\'s a little more than 2 feet. I found one that\'s 30 inches. Right in the middle of this, you drill a pilot hole and then screw in an hook screw. You hang your brooder lamp off this crossbar. I used my 250W fixture, but I removed the 250W IR bulb and put in a 100W flood light with a red lens. You want red, but no IR. I use the 250W IR for the coop in the winter.
Get several more pieces of 2 x 4 which you position diagonally to raise the crossbar and consequently the lamp. The 2 x 4 stack should form a V at one end of the box, then you run the crossbar at the opening of the V. No drilling or anything -- just lay them there.
Right now, I have a stack of three 2 x 4s and the temp is 90F in there. If it stays 90, I\'ll take a 2 x 4 off the stack (on each side) and thus lower the lamp 1 3/4 inches. That might get me to 95F for the first week.
After I\'m done brooding, I\'ll post the lamp heights for each 5 degree increment so as to eliminate some trial and error.
--Ron