Building a Low Tunnel

A low tunnel frame.One of the biggest challenges in having a winter garden is protecting it from the weather. Most people do not live in regions where the weather is perfect all year-round. So, in order to have a winter garden, most gardeners need some level of protection for their crops.

There are so many ways to protect your crops from the winter weather: greenhouses, high tunnels, low tunnels, cold frames, or a simple cover over wires. Each one of these options has its advantages and disadvantages, along with a wide range of expenses.

I decided to keep my system simple and inexpensive. I decided to use a low tunnel system held in place with a wooden frame. For one 4′ x 8′ tunnel system you are looking at about $25 for wood and conduit. Additional cost beyond the frame will depend on the type of cover you place over the frame.

My reason for using a wooden frame is to keep the tunnel together so in the winter I can lift one side of the tunnel and then harvest my crops. The wooden frame also gives me a place to secure the bottom of the cover material too.

If you are interested in build a tunnel like this, here are some step-by-step instructions on how to build a low tunnel with a wooden frame.

A bending form for a low tunnel.I wanted my tunnels to be a little over 4′ wide, so I built a homemade conduit bending form with some leftover 3/4″ plywood. Don’t worry if you don’t have access to the tools to build a bending form, Johnny’s Selected Seeds sells a metal version that works similar to the one I built.

A piece of conduit for a low tunnel.I used 1/2″ conduit to build my arched frames. I started with a standard 10′ length of conduit and measured in 5′ from one end and marked the middle of the conduit.

A piece of conduit in the low tunnel bending form.Next I lined up the midpoint of the conduit with the center line on my bending form.

A piece of conduit ready to bend.I then clamped the conduit to the bending form with a clamp and a wooden V block.

A piece of conduit bent on the low tunnel bending form.With the conduit secured, I pulled one side of the conduit around the form until half of the arch is made (the second clamp shown in the picture is only used to hold the conduit in place for the picture, this is not require). Once one side was bent I turn the conduit around and re-clamped the conduit to the form and bent the other side, just like the first side.

A piece of conduit bent for a low tunnel frame.A completed conduit frame. For my design I needed 4 bent conduit frames for each 4′ x 8′ tunnel. After all the pieces were bent I cut 12″ off of each straight leg of the frame to lower the overall height of the conduit frame. Note: I tried cutting two feet off the 10′ length prior to bending, but because each side is shorter there is less leverage to bend the conduit around the form, making the process much harder.

Wood for a low tunnel frame.Now with all the conduit frames bent it is time to start working on the wooden frame. The wooden frame will be used to hold the bent conduit frames in place.

Positioning the wood for the frame.

I started with 3 standard 2 x 4s that were 8 feet long, this will be enough wood to build one frame 4′ x 8′. Start by cutting one 2 x 4 in half, giving you two 4′ pieces. Next I drilled holes in the 8′ long pieces to receive the conduit frames. The first hole I drilled was in 2″ from the end to stay away from screws used to assemble the frame. Then, I drilled a second hole in 31″ from the first hole. I repeated this process on the other end of the 8′ piece as well. Once finished I had 4 holes on each 8′ long piece.

Once the pieces were completed I coated all the pieces with several coats of boiled linseed oil before assembly.

The wooden frame assembled.With all the pieces finished, it was time to start the assembly. I added some extra blocks in the corners for additional material to screw into (you do not need the extra blocks). I placed several screws in each end to secure the frame together.

Conduit in the wooden frame.Once the wooden frame was completed, I placed the bent conduit frames into the wooden frame. You can see a detail in the photo above of how the conduit fits into the wooden frame.

Completed low tunnel.

Now with the low tunnels complete, the only thing left to do is wait for the colder weather, place the frames over the garden plots and cover them with row cover then plastic as the weather gets even colder.

I will post more pictures as I begin placing the low tunnels over the garden and begin placing the covers over the frames.

I will also keep you posted on the status of these low tunnels as the winter gardening season progresses.

Happy Growing…

1 thought on “Building a Low Tunnel

  1. Thanks so much for sharing this. I’ve been contemplating covering and trying to go longer. Don’t think I’m going to make it this year, but maybe next time. Gathering info…

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