Constructed of PlexiglasTM and standard lumber using basic tools, this greenhouse is perfect for starting seeds, potting plants, storing tender bulbs and fragile containers during the winter, and performing other garden duties all year long.
Its finished size is compact enough to fit in even small backyards. Its arched roof and sloped sides are handsome and practical, with operable roof panels that can be propped open to let in fresh air.
Note: Unless otherwise noted, the greenhouse framework is constructed from 1x2 cedar lumber. If you have a table saw, consider ripping the 1x2s from wider material and select stock that is as straight-grained and free from knots as possible. The framework is cut and assembled in panels that are then joined to create the structure. All parts butt together and are fastened with 3-inch deck screws.
This greenhouse requires only basic skills and tools. Build the components, then assemble and screw them together.
2. To assemble one wing wall, cut 1x2 wall plates (A) and wall studs (B) to length. Lay out the pieces on a flat surface, square them up, clamp, and screw the studs between the plates 19-1/8 inches apart. Cut wall corners (C) and bottom plates (D) to length, then screw the corners to the wall assembly and to bottom plates (D) (photo 1). Leave a 1/4-inch gap between the two bottom plates and between the upper bottom plate and the lower wall plate (A). Cut and install the wall braces (E). Repeat for second wing wall; set the two assembled walls aside.
3. To assemble one sloped end panel, cut corner stile (F) to length; cut inner stile (G) a few inches longer than listed. Miter top ends of corner stile (F) and top plate (J) at 20 degrees; screw together. Cut end braces (H) and bottom plates (I) and drive screws to mount them between the stiles. Insert top plate (J) between stiles; clamp. Mark extra-long inner stile (G) for proper length, screw to top plate, then cut to fit (photo 2). Repeat for other sloped end panels (photo 2). Set aside.
4. To assemble one wing roof panel, cut the roof stiles (K) and roof rails (L) to length and screw panels together, checking them for square. Repeat for other three roof panels. Cut the hinge mounts (Z) to length and set assembled roof panels aside.
5. To assemble front and back panels, use the same procedure as for roof panels. Screw panel stiles (M) to the panel rails (N) and bottom plates (O). Do the same for the door stiles (P), door rails (Q), and base (R). Mount T-hinges and handle on the door.
6. To form roof arches (S) for center roof, lay out the curve on a 37-1/2-inch-long 1x10, as shown in the detail drawing. Bend a thin strip of metal or wood along the three nails to form the curve; mark with pencil. Cut curve with jigsaw. Mark a matching curve (parallel to the first) and the arch base to create the open space in arch as shown, then drill a pilot hole and cut out the waste with the jigsaw. Use this arch as a pattern to cut two more.
7. Dig postholes 30 inches deep or below your region's frost line. Place 6 inches of crushed rock in each hole, then fill with concrete. Insert galvanized tie-down straps while concrete is wet.
8. To make base frame, let concrete cure for several days, then cut 2/4 base frame pieces (T and U) to length and screw together, checking for square. Mount the base on the footings, making sure base is level.
9. Clamp one sloped end panel to the base so the top of inner stile (G) is flush with the top of panel stile (M). Check for level, then screw panel to the base. Set a wing wall in position and drive screws to mount it to the base and to sloped end panel (photo 4). Install other adjacent sloped end panel, making sure it's level. Repeat, installing the other wing wall and sloped end panels.
10. Cut posts (V) to length, position them plumb and screw in place against inner stiles (G) of the sloped end panels. Cut beams (W) to fit, then drive screws through inner stiles to hold beams on top of posts. With posts and beams in place, install front and back panel, door, and door stop (X).
11. Bevel one edge of each roof stringer (Y) on the table saw or with a hand plane.
Screw the arches (S) to the stringers; set the assembly on top of the beams and attach it with screws. Screw hinge mounts (Z) to the sloped end panels and beams. Screw two roof panel assemblies (K and L) to the hinge mounts (Z) of each wing.
Cut braces (AA) to length and miter the ends; check the structure for square, then screw braces in place.
12. To install the curved acrylic on center roof, drill pilot holes spaced 8 inches on center and 3/8 inches in from one long edge of the 42 x 84-inch acrylic panel. Temporarily use three screws to hold acrylic in place on one roof stringer (Y), then bend acrylic over arches to check it for proper width. Trim acrylic, if necessary; drive all screws along the first edge, then drill pilot holes at top of each arch. Drive screws through acrylic into arch tops before fastening down the other edge.
13. Screw acrylic pieces for wing roof panels to the roof stiles (K) and rails (L) as for the center roof panel. Screw two hinges to each upper roof rail (L). Position roof panels and fasten hinges to the hinge mounts (Z). Then install the lid supports to allow the panels to be raised for ventilation.
14. The acrylic for the walls, end panels, door, and back panel should be cut slightly (1/8 inch) smaller than the size of openings for ease in installation. Cut 3/8 x 3/8-inch square molding for acrylic stops to fit around each opening, and nail the pieces in place, using a scrap of acrylic to position them.
Place acrylic panels against square molding, then screw in acrylic retainer strips to hold panels in place (photo 11).