You do not need to have a lot of space to build a small greenhouse to use for starting garden plants or for having year-round harvest of cold-hardy greens. A backyard greenhouse can be very elaborate or quite simple in design, depending on your budget and your building skills. If your budget allows, you can buy a greenhouse kit that can be assembled in a few hours. Or you can build a functional greenhouse using low-cost PVC pipe and plastic sheeting using the following procedure.
Build the Base
Lay out the 1-by-6-inch boards to form a rectangular frame. Stand the boards on edge and attach them at the corners using wood screws. This will give you two halves of the frame (final dimensions are 10 feet by 20 feett). Align both halves forming a seam (joint). Center a wooden stake over each seam and secure with wood screws to complete the frame.
Place the remaining wooden stakes in each corner so that the pointed end is up and the flat end is flush with the bottom of the wood boards. Secure the stakes to the frame with wood screws.
Turn the rectangular box over and put it where you want your greenhouse. Use a hammer to pound the pointed ends of the attached wooden stakes into the ground, which should secure your frame in place.
Build the Frame
Measure and with the PVC piper cutter, cut the half-inch PVC pipes into 20 pieces 2 feet long (10 from each pipe). Place them along the sides of the greenhouse base. Start in the corners and place one every 4 feet by hammering it into the ground 6 inches. Secure to the frame using wood screws; that adds more stability to the base and a place to attach the ribs (hoops) of the greenhouse.
Measure and cut four 4-foot sections of three-quarter-inch PVC pipe. Cement a T-connector to the end of one piece and a 4-way connector to the other end, and add another section of pipe, another 4-way connector, and continue until all four pieces are assembled, with T-connectors on the ends. That forms the main supporting rib for the roof of the greenhouse. Be sure to cement each joint, and allow the cement to set before proceeding.
Slide five 10-foot-long pieces of three-quarter-inch PVC pipe over the one-half-inch PVC pipe on one side. Secure with wood screws. Repeat on the opposite side.
Connect the main rib you built earlier to the PVC pipes from both sides. Start at one end of the frame and apply PVC cement to the unattached ends of pipe. Use the supporting rib pieces to bring the PVC pipes together to form hoops.
Cover with greenhouse plastic sheeting. Attach at least 3 snap clips for each hoop to hold the plastic in place. Add more clips in windy areas or if high winds are expected. Gather excess plastic along the outside bottom of the sides, and cover with sandbags to hold it in place.
Slice the plastic on one end of the greenhouse to create a door. Attach Velcro to the edges of the greenhouse door so that it can be secured. Use sandbags against the bottom of the plastic to hold the doorway closed on cold, windy days.