I've been scrounging materials for our next coop for a while. It'll be nice looking, but low cost.
Lowe's had cedar boards on sale for half price. I bought all they had, and they're stacked in our garage.
There were big, very heavy-duty stainless steel hinges at our dump's scrap metal pile. They came off the doors of armored trucks.
A French glass door came from a house that was torn down.
There's drip-edge left over from building our house.
I have lots of exterior plywood scraps from dumpster-diving construction sites to use as gussets for roof trusses.
Biggest score: 4' x 4' Anderson awning windows from the town dump - still new in the boxes.
The floor will be dirt.
The roof will be sod. I've never done one before, and I'm looking forward to the experiment. I plan to put waterproof membrane over 2" tongue-and-groove, then 8" of soil. No shingles to buy, easy repairs if necessary, evaporative cooling in the summer and insulation in the winter.
The only things I have left to buy/scrounge are 4"x4"'s for the frame, lumber for the roof trusses and sheathing, the waterproof membrane, screws and some sort of finish, probably a clear preservative.