How to Build Your Own Lean-To or Attached Greenhouse
A Cost Effective Greenhouse That Connects To Your Home or Garage
The most practical of all greenhouses is one that becomes part of your house, construction is easier and the structure is better braced because one wall of the greenhouse is actually your house. This simple 8' x 12' lean-to greenhouse is framed with 2 x 4 redwood or cedar and covered with rigid polycarbonate panels. Once the foundation is complete and all the supplies are on hand two people can complete this lean-to greenhouse in a weekend. For energy efficiency it should be constructed around a door or window and insulated. For technical data how to apply, cut and clean polycarbonate panels visit our Lexan Corrugated and Thermoclear web pages. Compare the Clarity: Lexan Twin-wall vs. Lexan Corrugated polycarbonate. Use Western Red Cedar to frame your greenhouse because of it's resistance to rot and insects. At the Greenhouse Tips page there are potting bench plans, supplemental lighting and ventilation ideas, also info on preventing pests and diseases and Free Solar Greenhouse Plans for an evironmentaly friendly lean-to greenhouse.
Because this model is so light a simple foundation was chosen: precast concrete piers spaced 4 feet apart. When the concrete blocks are put in place with 2 inches showing above ground tie them together with a 2 by 4 redwood or cedar sill. Constructed in units the walls are nailed to the sill. The back wall is a house wall directly under an overhanging eave. One 2 by 6 ledger board 12 feet long is fastened to the house wall with lag screws driven into every other stud. To ensure a waterproof joint between the ledger board and the house galvanized metal flashing is tucked under the siding and draped over the ledger. The bottom of the ledger board is set at 8 feet high while the front wall at 6 feet. The front-wall of this lean-to greenhouse is vertical but you can angle it as shown for the solar greenhouse plans.
For a 6-foot-high vertical wall cut the studs 5 feet 9 inches long, this allows 3 inches for the top and bottom plates. The plates cut from 2 by 4s are the horizontal members to which the side-wall studs are attached at the top and bottom, the rafters lay across them at the top. To lay out the front-wall put the top and bottom plates side by side fiat on the ground. Mark off every 2 feet using a framing square to make marks on both plates at the same time. One of the legs of the square is 11/2 inches wide the same as a 2 by 4. Lay it over the center of the mark and pencil in lines on each side. Lay out the wall with plates and studs in place and then nail them together. Stand on one stud while nailing on the plate to keep the frame from shifting. Note that the on-center distance between the first stud and the second is only 23 1/4 inches. The extra 1/4 inch will be taken up outside by overlapping one extra ridge when putting on the corrugated plastic panels. You're now ready to stand up the first wall. With friends helping place the wall on the foundation and nail and brace it. Use a level to make sure the studs are vertical. Now you're ready to attach the side-walls. These go up essentially as the front-wall did.As with most lean-to greenhouse plans the vents are essentially frames to hold pieces of plastic paneling that fit between the studs or rafters. The following plans are for a roof vent. The vent in the front-wall is built in the same way but is covered with flat plastic panels to match the wall. Use 2 by 2s to construct a frame 24 inches long and 22 1/2 inches wide; this will fit exactly between the studs or rafters. Tack redwood corrugated molding or rubber molding on the top and bottom widths and attach a 28-inch length of rigid plastic roofing. The 4-inch overhang in front will prevent leaks. Since you cannot nail through plastic panels without breaking them lay them in place and drill holes with a 5/32-inch bit 12 inches apart down the rafters. Nail every third ridge on cross braces. The nail for attaching the polycarbonate panels is called a screw nail. It has a waterproofing washer attached and a wide screw thread, but you hammer it in. The nail should always be put through a ridge in the plastic rather than a gutter to prevent leakage. Don't hammer the nail in too far, just so the head and grommet are snug and secure with the plastic. From the back of the roof frame where the vent will hinge measure down 2 feet and attach a cross brace. The vent frame should fit smoothly into this opening. With it in place nail quarter-round molding to the rafters and braces right beneath the frame to support it. After the polycarbonate roofing panels are nailed in place with an allowance for the vent opening, install the vent and hinge it to the back plate. Use a hook and eyebolt to keep it from blowing open. With all the framing done and both vents completed, you are ready to complete the roof and cover the walls. At the top, along the ledger beard, and at the bottom, across the rafters and filler 2x4s nail on corrugated molding. The molding which follows the same waves as the corrugated plastic panels prevents drafts. On each rafter place half-round molding strips to support the plastic. If you use rubber or cedar / redwood molding lay a thin bond of sealant on the molding before you nail the plastic panels into place. Position the panels leaving a 2-inch overhang in front for water run-off. Cut the panels to fit flush with the vent opening. Across the front where there may be strong winds trying to pull the roof loose drive a screw nail in every ridge for extra insurance. It is better to cover the walls with flat polycarbonate panels. This makes a tighter fit under the roof line and flat panels are easier to cut than corrugated ones. Measure and cut the front panels first and nail them in place only after you are sure each panel is square. Lay a bead of sealant over each joint and then cover the joints with strips of redwood or cedar lats. These simple lean-to greenhouse plans should give you an idea of what you're up against if you want to build your own. I suggest getting blueprints and hiring a professional carpenter or contractor if you are going to attach a greenhouse to your home unless of course you are capable of such a task.