The Benefits of Building a High Tunnel

A simple high tunnel framework covered with plastic defeats inclement extremes and extends the vegetable gardening season.

| September/October 2012

Rain is pouring down — again. We’re already some 23 inches above average precipitation on the year, and it’s only September. However, my crops and I are nice and dry, thanks to the largest of the four high tunnels I built on our small farm in southeastern Pennsylvania.

What’s a high tunnel? It’s a poor man’s greenhouse. Instead of expensive glass and intricate steelwork, the structure consists of a simple frame — usually made of bent galvanized metal pipe or PVC pipe, though wood can be used. The pipes that form the “bows” or “ribs” of the frame fit into slightly larger diameter pipes that are driven two or three feet into the ground to form the foundation. Smaller PVC pipe is sometimes slipped over pieces of rebar hammered into the ground. The whole thing is then bolted together with baseboards, purlins, end-framing and doors to meet your needs.

The frames are covered with one layer of 6-mil UV-resistant greenhouse plastic. The plastic is attached with everything from expensive aluminum channels and “wiggle wire” to wooden lath, old fire hose, strips of inner tube, and even used drip-irrigation tape. The tunnels are not heated, but having an emergency heat source handy is cheap insurance for protection from extreme cold snaps, heavy ice or snow.

Whether you’re a backyard gardener, a market gardener or a commercial grower, you can build a high tunnel to meet your needs in just a couple of days using simple hand and power tools.

Benefits of building a high tunnel

The “high” part of the name means that the tunnel is high enough that you can stand up straight inside. “High tunnel” is a somewhat loose term. It includes everything from tall, Gothic arch structures to Quonset-style “hoop” houses, which also are known as cold frames. In tunnels with high sidewalls, there is plenty of room to operate garden tillers and even small tractors with tillers, mulch layers and bed shapers.

In extreme heat, the plastic skin can be easily shrouded in, or even replaced with, shade cloth. Add drip irrigation, minisprinklers and maybe a fan or two, and crops inside the tunnel will be almost as cool as veggies in the supermarket produce case.

Robyn Dolan
10/10/2012 4:55:53 PM

This sounds right up my alley. Rebar, pvc, plastic and shadecloth. I'm there.

9/3/2012 10:17:01 PM

All the on-line directions for hoop house seem to call for 6 mil "UV resistant" plastic and at least 3/4" pvc pipes. I used 1/2 inchers and standard 4 mil plastic (150 ' x 25' for ~$95). It worked just fine. If you roll the ends of the plastic fairly tightly on 1" x 1/2" slats and screw them into a 2 x 4 foundation frame, the tautness of the skin against the pipes gives the structure enough integrity to stand up to the worst spring Chicago thunderstorms. ..It was nice harvesting lettuce & radishes here in May when conventional gardens were just begining to become warm enough for planting.

Hans Quistorff
8/31/2012 7:49:32 AM

I use the frames from portable garages that the tarps have worn out and replaced the cover with construction plastic that has grommets to tie to the frame. Three rows of fall Raspberries are starting to produce now and should be available through November for the farmers co-op market. To answer the other comment: I have bumble bees in my tunnel for pollination and paper wasp bees for pest control. Some pictures

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