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Many backyard gardeners start growing plants indoors in late winter or early spring before the weather warms up.But the best way to start plants for spring gardening and extend the growing season into winter is to use a backyard greenhouse.Our design is a 6-by-8-foot structure that’s large enough to hold dozens of plants, yet compact enough to fit in the smallest yards.It’s also easy to build, requiring only basic woodworking skills and easy-to-use tools.You can do it in a few weekends.
The cost of materials to build our greenhouse is approximately $1,200.That’s higher than some pre-assembled greenhouses, but our material is more reliable than any ‘split’ model; plus, this one is customizable.We include a potting bench, overhead plant hanger and deck, but you can add or subtract features as you see fit.Whether you’re a professional gardener or a novice, our greenhouses will expand your gardening potential and diversify the variety of plants you can grow at home.
First cross-cut two pieces of pressure-treated 4×6 lumber to 8 feet long, and cross-cut the other two 4×6 pieces to 6 feet long.Mark half-lap joints 1 3⁄4″ deep x 5 1⁄2″ wide on both ends of all four pieces of lumber.Set the circular saw to a depth of cut of 1 3⁄4 inches and make precise 5 1⁄2 inch shoulder cuts in the wood from each end of the four 4x6s.Then set the saw to the maximum depth of cut and cut into the cheek from the end of the wood [1].
Flip the wood over and cut the other cheek to the other side.To complete the half-lap, trim the last bits of scrap wood with a reciprocating saw or handsaw.Repeat the cut half circle on each end of all four 4×6 pieces of lumber.Layout 6×8 feet.Timber frame foundation with overlapping half-lap joints at each corner.Measure the diagonal, check that the base frame is square, and adjust as needed; then secure each half-lap joint with two 3 1⁄2-inch long construction screws [2].
In this build, you will prefabricate the roof trusses that make up the greenhouse roof to simplify the framing process.Each truss consists of two angled roof rafters and a horizontal tie.There are five trusses: front and rear gable end trusses, and three intermediate trusses.Start by cutting ten 2×4 rafters to 52 1⁄2 inches long.Bevel the top of each rafter to 40 degrees; leave the bottom square off.Next, measure 2 1⁄2 inches from the bottom of the rafters and cut a small notch called a beak cut.These notches allow the lower ends of the rafters to sit flush on top of the side walls.
Also, measure 25 1⁄2 inches down from the upper end of each rafter and cut a 3⁄4 inch deep x 1 1⁄2 inch wide notch on the top edge of each rafter.Use a jigsaw to cut the sides of the groove 3⁄4″ deep, then use a hammer and 1 1⁄2″ wide chisel to chop away the scrap wood blocks.Once the truss is installed, these notches will accept 1×2 straps.
To assemble the truss, butt the 40-degree mitered ends of the two rafters together.Then glue and twist a 1⁄2 inch.Plywood gussets at the seams between the rafters [3].(We used yellow trim glue throughout the project.) Secure the gussets with 1 1⁄4 inches.Decorative screws.Repeat the above steps for the remaining four pairs of rafters.
For each of the three middle trusses, cut a 1×4 bow tie to 60 inches.Bevel each end of the bow tie to 50 degrees and glue it to the rafters with 1 5/8 inches.Decorative screws [4].For each of the two gable end trusses, cut the 2×4 ties to 56 inches long; bevel each end to 50 degrees.Set each tie centered and flush with the rafters, then screw it into place with 2 inches.Decorative screws.
On the rear gable end truss, add three small triangular 2×4 blocks.Place one in each lower corner, between the rafters and the tie [5], and one under the gusset in the upper corner.The blocks create a rough opening for operable vents.On the front gable end trusses, install two 13 5/8″ long vertical 2×4 blocks.Bevel the top end of the block to 40 degrees and slot the bottom end to fit snugly into the 2×4 tie.These two blocks provide firm support for the polycarbonate panels.
Use six 1x3s to make a frame for the vents.Cut the top 1×3 to 8 1⁄4 inches long and the bottom 1×3 to 36 3/8 inches; square the ends of each piece.Next, cut the two short side sections to 4 1/8 inches long, mitering their upper ends at 40 degrees.Finally, cut the two angled sections to 17 1/8 inches long; miter each end of the two sections to 40 degrees.
Assemble the vent parts, then glue and screw on 1⁄2″.The plywood gussets are passed through the top joints [6] and through the joints in each lower corner to a length of 1 1⁄4 inches.Decorative screws.
To make a greenhouse door that is 24 5/16″ wide x 76 3⁄4″ high, start by cutting two 1×3 vertical fences to 76 3⁄4″ long.Next, cut the three horizontal rails to 19 5/16 inches long; cut the head and middle rails from 1×3 and the bottom rail from 1×4.
I connected the door frame parts using board connectors to cut slots for compressing the beech biscuit splines.Position the top edge of the middle rail 37 1⁄4 inches from the head rail.After cutting the corresponding slots on the parts, I glued the slots, inserted the cookies, and clamped the frame together [7].If you don’t have a board connector, glue and screw in 1⁄2″.Plywood gusset 1 1⁄4 in. across seam.Decorative screws.Let the glue cure overnight.
All four walls of the greenhouse are framed with 2×4.Cut the horizontal top and bottom plates (bottom plates) of both side walls to 8′ lengths.For the rear wall, cut the top and bottom panels to 65 inches.Next, cut five 2×4 studs for each side wall and four studs for the back wall, to 65 1⁄4 inches.To assemble the wall, drive two 3″ trim screws through the top and bottom plate and into each wall stud [8].
To frame the front wall that includes the doorway opening, you’ll need ten 2×4 pieces: cut the bottom plate to 65 inches, then cut two double 2×4 top plates.Each double top plate consists of one 18 5/8-in.-long 2×4 and one 17 3⁄4-in.-long 2×4.Next, cut two wall studs to 65 1⁄4″ long and two trim bolts to 75 3⁄4″ (Trim bolts form the rough opening for the door.) Finally, cut one 27 3⁄4″.- Long 2×4 temporary header that spans the top of the trimmer stud.Screw the parts together with 3 inches.Decorative screws.After wall mounting, remove the connector.Apply a solid color stain to all surfaces of each part using a paint pad [9].Let the stain dry overnight.
Doing this to the wall frames before erecting them will save you time and trouble.Begin by peeling off the clear protective film from the back of each polycarbonate panel.Lay the polycarbonate on the wall, starting at the center of the wall frame.Make sure all seams are aligned with the center of the studs, but leave 1/8 inch.Expansion gap between panels.Fasten the polycarbonate panels to the wall framing with 1 1⁄4 inches.Decorative screws are spaced approximately 16 inches apart.
Slide the polycarbonate panels into each end of the wall frame [10], then use a router equipped with a flush trim bit to cut away the overhanging polycarbonate [11].A router provides the fastest and most accurate way to trim polycarbonate, but if you don’t have a router, put the polycarbonate panel in place, mark where it overlaps the wall frame, and use a circular saw or jigsaw.
Set the wood frame foundation on the ground and use 4 feet.level to confirm that its width and length are horizontal.If necessary, dig out or pile up the underlying soil until the frame is level.Next, drill holes 1⁄2″ in diameter through the wood frame, about 24″ apart.Use a small sledgehammer to drive 1⁄2″ diameter x 18″ long rebar through the hole into the ground [12].The railing will prevent the foundation from moving.Cover the ground within the wood frame with landscape fabric; then add 3 inches of gravel or bark mulch to form the floor.
Install the precast wall, starting with one of the side walls.Stand the wall on a wood frame foundation, aligning the base plate with the outside edge of the 4×6 foundation wood [13].Secure the wall to the foundation by driving 3 inches.The deck is screwed down through the bottom plate into the 4×6 [14] below.Space the screws about 24 inches apart.Repeat for the opposite side wall.
Lift the rear wall, slide between the two side walls, and confirm that the wall is vertical.Screw the back wall to the foundation with 3 inches.Drywall screws, then through the studs on each end of the rear wall into the side walls [15]; space the screws 16 inches apart.Repeat the installation of the front wall [16].Then use a handsaw or reciprocating saw to cut through the 2×4 base plate through the door sill.
Roof trusses were added by angling the rear gable end trusses into place at the top of the rear wall [17].Align the truss with the outside edge of the wall and drive 3 inches.The trim goes through the top plate and into the beak on each rafter.Then install the three intermediate trusses, making sure to place each truss on the wall studs [18].Fasten each middle truss as you would a gable end truss: screw into the top plate at a slight angle and into the beak cutout [19].
Set the front gable end truss on top of the front wall and tilt it into place [20].Drive 3 inches.Drywall is screwed into each rafter through the top plate, then two 3″ trusses are attached.Metal L-bracket.Thread the bracket onto the top of the trimmer stud and screw in the 2×4 tie [21].
Before attaching the polycarbonate roof panels, place 1×2 straps into the grooves on the top edge of each rafter.Secures shoulder straps by driving a single 1 5/8″.Trim screws go through the 1×2 and into each rafter [22].Then install a 2×4 block between each pair of rafters [23] to close the space between the top panel and the underside of the polycarbonate roof panel.
Fasten the polycarbonate panels to the rafters with 1 1⁄4 inches.Decorative screws, 16″ apart [24].Continue to install panels on the rafters on both sides of the roof, leaving 1/8″.Gap between each panel.Once all the roof panels are in place, use pressure treated 1×8 and 1×10 to make the ridge caps, each 99 inches long.First, use a circular saw or table saw to rip the 1×10 to 8 inches wide.Then bevel a 10 degree bevel to one edge of the 1×8.Twist the two boards together to place the ridge cap on top of the greenhouse roof.Hold it in place by driving 1 5/8″.Deck screws down into the rafters [25].
To help create a weatherproof roof, apply a continuous bead of silicone sealant to the seams between the polycarbonate panels.Then cover each seam with a 1×2 slat [26].Secure the slats with 1 5/8″.Trim head screws 16 inches apart.Repeat the process to apply the battens to the vertical seams of the greenhouse walls.
Add a 1×4 enclosure around the doorway opening, then hang the door with two self-closing hinges [27].Install hinges 6 inches from the top and bottom of the door.Then install the automatic vent opener by screwing it onto the vent frame and 2×4 tie [28].
For the three mounting brackets for the potting bench, cut two horizontal 21 1⁄4″ long 1×4 bench brackets and one 25 3⁄4″ long 2×4 diagonal bracket.Trim one end of the six 1x4s to 45 degrees and the ends of the three 2x4s to 45 degrees.Glue and screw a 1×4 to each side of the 2×4 to create a 45 degree diagonal support.(You’ll use 1 5/8-inch trim screws on the potting bench.) Slide each mounting bracket onto one of the sidewall studs.Position the bracket 35 1⁄4 in. above the wood framing foundation and fasten it to the side of the wall studs [29] with horizontal 1×4 screws.Then thread a single screw through the mitered lower end of the bracket and into the edge of the wall stud.
Since there is no way to attach the mounting brackets to the studs on each end of the side walls, screw a 1×4 cleat to the two studs on the front and rear walls.Place each splint at the same height as the mounting bracket: 35 1⁄4 inches.on the basis.These support 1×4 potting slats.
Use four 96″ long 1×4 slats to make the surface of the potting bench.Thread the slats through the mounting bracket and cleat 1⁄2″ apart, then secure them with 1 1⁄4″.Decorative screws [30].
Complete the interior of the greenhouse by installing overhead poles for hanging plants and baskets.Cut 1⁄2″ diameter metal conduit to 94″.Drill a 1⁄2″ diameter x 1″ deep hole in the 2×4 bow tie of the front and rear gable end trusses. Position the hole 12″ from the end of the tie.Slide the conduit into the hole and secure it to the underside of each 1×4 bow tie with a conduit strap [31].
For the deck frame, cut two 2×4 x 72 inches.With joists and five 2×4 x 20 1⁄2 in.Floor joists.Tighten the floor joists between the two strip joists by 3 inches.Galvanized deck screws, spaced 16 1/8 inches apart, to create deck framing.Set the frame in front of the doorway and fasten it to the wood frame foundation with four 3 1⁄2 inches.Structural screws.Support the outer two corners of the deck frame with concrete blocks or pressure-treated posts to keep the deck level.
Cut into four 5/4-inch pieces.x 6 inches.Pressure treated deck to 72 inches long.Lay the floor on the floor frame at 1⁄2″ intervals [32].Fasten the deck to the deck frame with 2″.Decorative screws.Now, with your greenhouse complete, bring the plants in and watch them grow!
Post time: Jul-14-2022