Abstract: Greenhouse or storage structures in several embodiments of different sizes are capable of being mass produced in major subassemblies and then shipped knocked down and flat to a final erection site. Then they are erected in a matter of minutes by one person in respect to smaller ones and in less than two hours by two persons in respect to larger ones. Each greenhouse has a combined wall and roof assembly comprised of semi-rigid sheet material, generally fiberglass, originating in a rectangular shape. Using respective jigs, these rectangular sheets are laid over and fastened to several spaced and parallel pieces of flexible plastic conduit, which serve jointly as wall and roof reinforcements or supports. These flexible plastic reinforcements are aligned transversely to the longitudinal axis or each greenhouse. They also extend beyond the edges of the fiberglass sheet on both sides.