Project Guide

How to Build a Greenhouse

Assemble the Base and Corner Uprights
A person assembling the base and corner uprights of a greenhouse.

The greenhouse back wall features two longer base rails, while the front of the base frame side will have two smaller base pieces. Connect these two using a third middle piece to create the threshold for the greenhouse door.

  • Before starting assembly, decide which end of the greenhouse you want as the entrance.
  • Separate out the pieces needed to construct the rectangular base and the four corner uprights.
  • The corner uprights will have two smart lock connectors protruding out at the base forming a 90-degree angle.
  • Attach the side base pieces onto the connectors on the corner uprights, then connect the four corner assemblies using the middle base pieces.

Tip: Use a spray lubricant for snug-fitting connectors. 

Safety: Have a friend help you assemble your greenhouse – many steps will require assistance lifting and holding parts steady.

Attach the Roof Frame
A man attaching a roof frame to a greenhouse.
  • Find the four shorter pieces with three smart lock connectors at one end. Attach these to the tops of the corner uprights. These rails will form part of the top of the front and back walls.
  • There will be connectors angling up at a 45-degree angle that will help tie the roof trusses together with the rest of the frame.
  • The front and back roof trusses connect at the peak and can be lifted into position with an assistant and placed onto the diagonal connectors.
  • Assemble the three piece ridge beam according to manufacturer’s instructions. Snap both ends into the connectors at the top of the front and back roof trusses.
Install Wall Uprights and Roof Rafters
Person on ladder installing greenhouse wall uprights and roof rafters.

You must assemble the frame in this order to keep the structure stable during the building process.

  • Begin constructing the frame of the walls by connecting the three pieces that form each of the upper wall rails.
  • Connect these assembles to the tops of the former corner uprights at each end.
  • Hammer in place with a rubber mallet.
  • Attach the two center uprights to the base rail following manufacturer’s instructions.
  • Tighten the base connections but don’t attach the tops yet.
  • Install the four roof rafters over the four wall uprights you just installed. They will attach to the ridge beam on top by lining up the bracket holes and inserting a bolt.
  • There will be similar brackets for attaching the bottom of the roof rafters to the upper wall rail.
  • Use the spacer to make sure you place the three remaining uprights on each side correctly, then install.
  • Repeat the process when installing the corresponding roof rafters.
  • The two front and back wall uprights attach to the base rail in a similar manner.
  • Attach these to the roof trusses by inserting a plastic knob into the bracket and twisting right to tighten.

Tip: Using the spacer ensures the panels will fit properly when they’re installed.

Install Wall Panels
Person installing greenhouse wall panels.
  • Begin at one corner and insert the first wall panel, sliding in from the top along the channels of the wall uprights.
  • Continue installing the panels until only the two center back walls remain.
  • Attach an extended wall upright to the rear base frame.
  • Slide in the remaining wall panels, then slide in the panels that will enclose the area under the roof trusses.
  • Install crossbeams after each level of panel is installed.
  • Attach the outer crossbeam and truss covers once the gables and walls are complete. This will seal the seams and help waterproof the greenhouse.

Tip: The panels are designed to fit snugly, so don’t expect them to slide smoothly into the channels. 

Install Ventilation Windows (Optional)
Person installing optional ventilation windows for greenhouse.
  • Attach windows by hooking into the groove on the ridge beam.
  • Install the crossbeam between the rafters at the base of the window and secure the crossbeam to the neighboring rafter beams with bolts.
  • Attach the handle once the windows are installed.
  • Slide the remaining roof panels in position.
Install Doors
Person installing doors for greenhouse.
  • Position the hinge hardware on the door jambs, aligning them with the predrilled holes.
  • Fasten with screws.
  • Attach the handles to the door.
  • Attach the two top and bottom hinges according to the spacing indicated in the manufacturer’s directions.
  • Have an assistant help you hold the door in place while you attach it to the door hinges.
Install Supports
Installed greenhouse suppports.

Additional supports provide stability to the greenhouse. Anchor these supports to your foundation using screws. 

If your foundation is concrete, use a hammer drill. Customize your greenhouse by adding accessories such as shelves and hooks throughout the space.

Building a DIY greenhouse pays off well for the avid gardener. There are many greenhouse designs that will beautify your garden as well as protect your plants. For more guides on garden improvements, check out our helpful advice on planting new trees, creating a planter wall and building a hexagon planter.