Small Garden Greenhouse: Part 1

I used a 4-foot-by-8-foot piece of wood lattice as the shelf in my first greenhouse; I replaced it a year later with plastic lattice. Both proved too flimsy. In this design I used 3/4-inch thick cedar lattice. I like lattice because it allows some light to shine through, and spilled water doesn’t puddle on its surface.

Materials List

• 1 4-foot-by-8-foot sheet of 3/4-inch lattice (plant shelf)
• 1 30-inch wooden screen door
• 2 4-foot-by-8-foot sheets of 3/8-inch plywood (top and bottom of base)
• 3 8-foot 2-by-4s (perimeter of base)
• 7 8-foot 1-by-4s (interior of base frame)
• 5 8-foot 1-by-3s (support frame for plant shelf)
• Total 8-foot 1-by-2s = 40 (sort carefully at the lumberyard or buy several extras)
12 8-foot 1-by-2s (back wall)
8 8-foot 1-by-2s (end walls)
11 8-foot 1-by-2s (rafters)
6 8-foot 1-by-2s (plates)
3 8-foot 1-by-2s (window frame)
• 1 10-foot 1-by-2 (ridge pole)
• 2 10-foot treated 2-by-4s (skids)
• 2 3-inch eye bolts with nuts and washers
• 2 tubes construction glue
• 1 heat-activated opener
• 120 linear feet of batten tape
• 10-foot-by-30-foot greenhouse plastic
• Approximate numbers of screws:
100 11/2-inch exterior screws
50 2-inch exterior screws
100 3-inch exterior screws
20 3 1/2-inch exterior screws

Construction notes

The strength and rigidity of the torsion box that forms the base of the greenhouse require only that the frame pieces fit snugly together and provide a level base for the plywood until the glue sets. The completed base weighs about 140 pounds so you might want help moving or tipping it to attach the plastic and skids to the underside. The upper frame is amply strong for its intended purpose, but it is best not to use it as a lever to tip the base.

The upper frame’s joints are “crowded” with screws. If you hit a screw while drilling a pilot hole, adjust the angle of the bit until it clears.
Greenhouse plastic is damaged by oil-based paint; use latex coatings only.

Base construction

First, make a frame by cutting two 45-inch 2-by-4s and fastening them to two 8-foot 2-by-4s (shorter ends between the longer sides) using two 3 1/2-inch deck screws at each corner as shown in Figure 2. Next, mark three 93-inch-long 1-by-4 stringers shown in red and fasten them inside the frame at the points marked on the ends using two 3-inch deck screws at each joint.