How to Create a Backyard Greenhouse

Many backyard gardeners start their plants indoors in late winter or early spring before the weather warms. But a backyard greenhouse is the best way to jumpstart plants for spring gardening and extend the growing season into winter. Our design is a 6-by-8-foot structure, large enough to accommodate dozens of plants but compact enough to fit in the smallest yard. It’s also easy to build, requiring only basic carpentry skills and easy-to-use tools. You can finish it in a few weekends.

The materials to build our greenhouse cost about $1,200. That’s more than some pre-assembled greenhouses, but our materials are more reliable than any “snap-together” model. In addition, it is a custom. We include a potting bench, overhead plant hanger, and deck, but you can add or subtract features as needed. Whether you’re an expert gardener or a beginner, our greenhouse will expand your gardening potential and diversify the types of plants you can grow at home.

Cut the wood frame foundation.

Start by cutting two pressure-treated 4×6 lumber 8 feet long, and two other 4x6s cross-cut to 6 feet long. Mark both ends of all four lumber for a 1 3⁄4-in.-deep x 5 1⁄2-in.-wide half-lap joint. Set the depth of cut on your circular saw to 1 3⁄4 inches, and make a precise 5 1⁄2 inch shoulder on the wood from each end of the four 4x6s. Then set the saw to its maximum depth of cut and cut the cheek with the end of the wood [1].

Flip the wood over and cut another cheek on the opposite edge. To complete the half-lap joint, cut the last piece of scrap wood together with a saw or hand saw. Repeat to cut half laps into both ends of all four 4×6 lumber. Lay out the 6×8-ft. Wooden frame foundation, half lap joint overlapping each corner sitting. Measure the opposite diagonal to check that the perimeter of the foundation is square and make adjustments as needed. Then secure each half-lap joint with two 3 1⁄2-in.-long structural screws [2].

Build roof trusses

In this build, you will pre-fabricate the roof trusses that frame the greenhouse roof to simplify the framing process. Each truss consists of two angled roof rafters and a horizontal collar tie. There are five trusses in total: front and rear gable end trusses, and three intermediate trusses.

Begin by cutting ten 2×4 rafters to 52 1⁄2 inches. Cut the top end of each rafter at 40 degrees. Skip the bottom end square. Next, measure 2 1⁄2 inches from the bottom of the rafters and cut a small notch called a bird’s mouth cut. These notches allow the lower end of the rafters to sit flush against the side walls.

Also, measure 25 1⁄2 in. down from the top end of each rafter and cut a 3⁄4-in.-deep x 1 1⁄2-in.-wide notch on the top edge of each rafter. Cut the 3⁄4-in.-deep sides of the marks with a jigsaw, and then cut the blank wood block with a hammer and 1⁄2-in.-wide chisel. These marks will accept the 1×2 strap when you install the trusses.

Read More: How To Build a Raised Garden Bed 2022

To assemble the trusses, butt the 40-degree mitered ends of the two rafters together. Then glue and screw the 1⁄2-in. Plywood gusset plate at the joint between rafters [3]. (We used yellow decking glue in this project.) Fasten the gussets with 1 1⁄4-in. Decking screws. Repeat for the remaining four pairs of rafters.

For each of the three intermediate trusses, cut a 1×4 collar tie to 60 inches. Cut each end of the collar tie at 50 degrees with a miter, then glue and screw it with a 1 5/8-in. Decking screws [4]. For each of the two gable end trusses, cut a 2×4 collar tie 56 inches long. Cut each end to 50 degrees. Set each collar tie on center and flush with the rafters, then screw it in place with 2-in. Decking screws.

To the rear gable end truss, add three small triangular 2×4 blocks. In each lower corner, place between the rafter and collar tie [5], and one upper corner under the gusset plate. The blocks create a rough opening for an operable air vent. At the front gable end truss, install two 13 5/8-in.-long vertical 2×4 blocks. Cut the top ends of the blocks at 40 degrees, and mark the bottom ends to fit snugly over the 2×4 collar tie. These two blocks help fasten the polycarbonate panels.

Cut and assemble the air vent frame.

Make the frame for the air vent from six 1x3s. Cut the top 1×3 to 8 1⁄4 inches long, and the bottom 1×3 to 36 3/8 inches. Cut both ends of each piece square. Next, cut the two short side sections 4 1/8 inches long, mitering the top ends to 40 degrees. Finally, cut the two angled sections to 17 1/8 inches long. Miter each end of the two halves at 40 degrees.

Assemble the air vent sections, then glue and screw the 1⁄2-in. plywood gusset plate at the top joints [6], and across the joint at each lower corner, with 1 1⁄4-in. Decking screws.

Add the roof trusses by bending the rear gable end truss in place above the rear wall [17]. Align the truss flush with the outside edge of the wall, and drive 3-in. Decking screws up through the top plate and into the bird’s mouth cut in each rafter. Then install the three intermediate trusses, making sure to place each one above the root of the wall [18]. Fasten each intermediate truss as you did the gable end truss: screw the top plate at a slight angle and into the bird’s mouth cut [19].

Sheet the roof.

Before attaching the polycarbonate roof panels, strap a 1×2 into the notches cut into the top edge of each rafter. Secure the strap by driving a 1 5/8-in. Decking screws through the 1×2 and into each rafter [22]. Then place a 2×4 block between each pair of rafters [23] to close the space between the top plate and the bottom of the polycarbonate roof panel.

Fasten the polycarbonate panels to the rafters with 1 1⁄4-in. Decking screws, 16 inches apart [24]. Continue paneling the rafters on each side of the roof, leaving a 1/8-in. difference between each panel. Once all the roof panels are in place, create a ridge cap using 1×8 and 1×10, each 99 inches long. First, use a circular or table saw to cut the 1×10 to 8 inches wide. Then rip a 10-degree bevel into one edge of the 1×8. Bring the two boards together and set the ridge cap on the top of the greenhouse roof. Secure it in place by driving a 1 5/8-in. Screw the bottom decking in the rafters [25].

Add the batons.

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 1×2 batting [26]. Fasten the battens with 1 5/8-in. Trim head screws, 16 inches apart. Repeat the batting process at the vertical seams in the greenhouse walls.

Unscrew and remove the door.

Add 1×4 exterior casing around the door opening, and then hang the door with two self-closing hinges [27]. Install hinges 6 inches from the top and bottom of the door. Next, install the automatic vent opener by screwing it into the air vent frame and the 2×4 collar tie [28].

Build a potting bench

For the three mounting brackets of the potting bench, cut two horizontal 21 1⁄4-in.-long 1×4 bench supports, and one 25 3⁄4-in.-long 2×4 diagonal brace. Cut one end of six 1x4s to 45 degrees and both ends of three 2x4s to 45 degrees. Glue and screw a 1×4 to each side of the 2×4 to create a 45-degree diagonal brace. (You’ll use 1 5/8-inch decking screw for the potting bench.)

Slide each mounting bracket over a stud in a sidewall. Place the brackets 35 1⁄4 inches above the wood frame foundation, and fasten them through the horizontal 1x4s and into the side of the wall studs [29]. Then drive a single screw through the bottom of the brace and up to the edge of the wall stud.

Since there is no way to attach the mounting bracket to the studs at each end of the sidewall, screw a 1×4 cleat to the two studs in the front wall and the back wall. Place each cleat at the same height as the mounting brackets: 35 1⁄4in. above the base. These support 1×4 potting bench slats.

Make the surface of the potting bench with four 96-inch-long 1×4 slats. Set the slats on the mounting brackets and cleats 1⁄2 in. apart, then fasten them with 1⁄4-in. Decking screws [30].

Add an overhead plant hanger.

Complete the interior of the greenhouse with an overhead bar for hanging plants and baskets. Cut a length of 1⁄2-in.-diameter metal conduit to 94 inches. Drill 1⁄2-in.-diameter x 1-in.-deep holes in the 2×4 collar ties in the front and rear gable end trusses.Space the holes 12 inches from the ends of the collar ties. Slide the conduit into the holes, and then secure it with a single conduit strap under each 1×4 collar tie [31].

Fabricate and install pressure-treated decks.

For the deck frame, cut two 2×4 x 72-in. band joists, and five 2×4 x 20 1⁄2-in. Floor joists. Screw the floor joists between the two band joists with 3-in. Galvanized decking screws, spaced 16 1/8 inches apart, to form the deck frame. Set the frame in front of the door and attach it to the wood frame foundation with four 3 1⁄2-in. Structural screws. Support the outer two corners of the deck frame with concrete blocks or pressure-treated posts to hold the deck level.

Cut four pieces of 5/4-in. x 6-in 72-in long pressure-treated decking. Lay the trim on the floor frame, 1⁄2 inch apart [32]. Fasten the decking to the deck frame with 2-in. Decking screws. Now, with your greenhouse complete, bring in the plants and watch them grow!

How to Create a Backyard Greenhouse

Do greenhouses work in the winter?

Yes, greenhouses work in the winter, but you need to plan for specific types of crops. Root and leafy vegetables are best grown in winter, and if temperatures drop significantly you may need to introduce some heat source.

How much does it cost to build a backyard greenhouse?

A greenhouse makes it possible to grow plants all year round. Greenhouses can cost anywhere from $500 to $35,000 to build, with the average greenhouse costing about $9,573. Greenhouses are enclosed structures, usually built in backyards, that provide shelter for plants to grow.


Hello My self Emelia , I'm a Technology & Gaming Guides Expert. OR Also Providing Gaming Guides For Public information.

Related Articles

Leave a Reply

Your email address will not be published. Required fields are marked *

Back to top button