Some easy-to-follow greenhouse plans call for using old windows or doors as building materials to construct a shed or lean-to. Other ideas include using cattle fencing panels, polyurethane sheeting and lumber to build a hoop house.
Two inexpensive, readily available materials for building greenhouses are used window frames and used screened or storm doors. Whether the panes are intact or not, these frames can be fixed together on framing studs on a foundation of used wooden pallets or cinder blocks and gravel. Use polyurethane sheeting to cover missing glass or add a layer of insulation.
To construct a hoop house, a long narrow greenhouse with a rounded, arched roof, you need panels of cattle fencing, polyurethane sheeting and some lumber to frame a door. Although you can construct a foundation, the metal ends of cattle fencing can be stuck directly into the ground. Bend one fencing panel into the shape and height of the arch you need. Bend other sections to match. Secure the bottoms of the arches in the ground. Cover the arch with polyurethane sheeting, securing it with zip (cable) ties. For a simple door, make a flap at one end of the greenhouse, or use lumber to build a simple door frame, and staple plastic sheeting to it.