We used pallets for the floor and walls, left the front open with a tarp that hangs over the open front and put plywood in top for lean-to type roof and had spare shingles so put them up. Been using that for almost 10 years. Good air flow... kindling in one side wood on other. Pallets around us, free for the taking. Most manufacturing plants give them away. So other than a couple pieces of plywood...free.