Why buy a greenhouse if you can make it yourself? Especially if it is much cheaper? A cool shed like this can be done very cheaply. The main materials needed are old replacement windows, an old door, a few pieces of wood for rafters, and some polycarbonate roofing sheets. IDEA: Rather than throwing away your old windows, door, and other materials, turn them into a greenhouse shed.
Stand the timber upright on its edge and push and pull it backwards and forwards across the frame while dragging it from one end to the other and this will level it roughly. Next, lift the board at both ends about 4 inches above the frame and tap it back down on the frame, moving up and down the frame as you do so. Try and tap together so both ends of the board hit the frame at the same time.
Well, not these plans. You have the option of building a very functional and spacious lean-to shed on different foundations. Your foundation choices are: concrete slab, a wooden floor supported by concrete piers, or a wooden floor supported by skids. That lost option also means that your lean-to could be mobile as well so you won’t have to decide where you want to permanently put it.