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How to Build Caterpillar Tunnels for Just 30 Cents per Square Foot!

Erin Southwood grew up around gardening. Her family had an urban garden when she was growing up, so it was a natural fit for Erin to have a garden in her small urban yard as well.

From there, Jamie asked her grandparents for a patch of dirt on their farm. Grandpa tilled a 10’x50′ plot for Erin, plus invited her to use some of theirs as well.

In 2016, Jamie, along with her parents, left their urban gardens to take on a much bigger gardening adventure: they bought grandma and grandpa’s 20 acre farm in central Indiana.

A lifelong love of gardening, the outdoors and growing things, is now a passion blended turned into a family farm business.

This (2017) is our third season growing for market.

This year Erin and company set up caterpillar tunnels for the first time to expand their growing season and space. Here they share what kind and size of grow tunnels they built, how much it cost and what materials they used, plus what they’re planning for future.

DIY caterpillar tunnel
Erin Southwoods caterpillar tunnel exterior, before she tapered the ends.

 

Caterpillar tunnel for plants
Erin Southwood’s DIY Caterpillar Tunnel Interior with LOTS of room for plants!

DIY Caterpillar Tunnels

Mom and daughter were able to build two caterpillar tunnels for under $450 or 30¢ per square foot, with enough plastic leftover to throw over an existing cattle panel trellis for a little extra seedling space. We’ve recently installed cattle panel tunnels, but seeing Erin’s success with these much larger better versions of a variation on the high tunnel caterpillar greenhouse, has boosted our confidence.

We’re now ready to just dive in and do this too as soon as we can find (or create) a level enough space to do it. (Our challenge is that most of our land is in the woods and/or on a hill). Like Erin, we have poor soil, so another advantage of the caterpillar tunnel will be to help us cultivate raised beds as we begin to replenish our soil with bagged soil gardening and mulch over time.

Okay! Now let’s get on with the specifics!

 

How to Build a Caterpillar Tunnel Greenhouse

By Erin Southwood of LibertyHeritageGardens.com

It’s awesome of Erin to lay out all her specs on building her caterpillar tunnel. That’s one of the many things we love about gardening and farming: they tend to be a sharing bunch, where each ones lessons are freely shared to help others start out ahead of the learning curve.

Editor’s Note: To save you time, many larger home centers like Lowe’s and Home Depot can shop your order for you. Imagine faxing this list to your local home center, then driving up to pay and load it without having to take the time out to pull it all. Another thanks to Erin’s awesome list to make it easier for all of us!

So your best, cheapest solution is your local home store. However, if you don’t have one close by, or end up missing some odd pieces here and there, Amazon is a great “back pocket” solution. If you have Amazon Prime, many things you order can be shipped to your doorstep for free. So for your convenience and the pocket change to help keep our site up, we provide our affiliate links

Caterpillar Tunnels Size

  • 1 – 12’x75′ caterpillar tunnel
  • 1 – 12’x50′ caterpillar tunnel

Yes, it’s PVC. No, it’s not greenhouse plastic. But it’s what we could afford and hoping to make it last through at least one season and make enough money to build better structures next year. This is our third season growing for market, and my mom and I built these on our own from scratch. Thought I’d share for those just starting out and who—like us—are trying to do a whole lot with very little. It can be done!

We built our own grow tunnels for 30¢ per square foot!

 

Materials

  • 1″ Schedule SDR* 21 PVC**, 10′ lengths secured with…
  • Couplers and…
  • PVC cement
  • 5/8 rebar (bought 20′ lengths and used angle grinder to cut down to 30″ lengths; each PVC end inserted over 5/8 rebar)
    • 5′ spacing between ribs
  • 3/8 rebar cut to 24″ lengths next to each PVC to secure twine over top of plastic…each cross over is it’s own section of…
  • Baler twine so if one snaps the whole thing doesn’t come down
  • 6 mil clear plastic
  • Purlin

Erin’s tunnels are running north/south and the wind usually comes from west/southwest. They haven’t needed any bags or anything to weight down the tunnel. Erin say it withstood some hefty winds following a storm. She thinks that the rolled up plastic at the base filled with water, which likely helped to weight it down.

*SDR means Standard Definition Ratio
**PVC means polyvinyl chloride

Caterpillar tunnel
Caterpillar tunnels ribs.

RIBS

  • Spaced 5’ apart
  • 1” schedule 40 PVC 20’ length
  • Insert rib ends over 5/8 rebar, 30” lengths driven at least 18” into ground
  • Can use (1) 20’ PVC or (2) 10’ PVC connected with couplers and PVC cement
  • 12’ tunnel width

PURLIN

  • How Erin adjusts tension on purlin.

    3/8” hollow braid polypropylene, any strong rope that will not easily stretch will do

  • Drive a T-post stake into the ground about 8’ out from each end rib. Stake should be at an angle away from the tunnel.
  • Tie rope to one T-post stake and wrap around each rib in tunnel, tie off at T-post on opposite end of tunnel.
  • It helps if your purlin is adjustable, some way to tighten the purlin as needed would be ideal. See picture on this post showing how we made ours adjustable.

CROSS OVER TIES

  • How cross over ties are attached to rebar.

    3/8 rebar, 24” lengths, driven 18” into ground at the base of each rib end. Drive them into the ground at an angle away from the tunnel.

  • Baler twine for cross over ties. Each crossover is a single section of twine so if one snaps the whole structure doesn’t come undone.
  • Criss-cross the ties over the plastic, from an overhead view it will be an “X” shape between each set of ribs.
  • When needed, you can tighten the cross over ties by winding them around the rebar at the base of each rib.

Note: See Erin’s video below on how to tighten cross over ties.

 

PLASTIC

  • 6mil clear plastic, 24’ width gives 2’ to work with on each side using 20’ ribs, having that extra 2’ on each side helps if weights are needed along sides
  • Use a roll of plastic approx. 24’-25’ longer than the length of your tunnel (we used a 100’ roll to cover a 75’ tunnel).

TUNNEL ENDS

  • End ribs are angled away from tunnel, about 45 degrees or so.
  • These angled ribs are (2) 10’ sections of PVC connected with a Tee and PVC cement. (the tee is used to connect a brace).
  • Add a smaller hoop after angled rib to help hold plastic taught (helpful for high winds). We used ½ “ PVC for this.
  • Use ½ PVC to brace the angled rib against the ground (this is where that tee comes in). So you’ll have a ½” PVC connected to the tee on angled rib and running to the ground, this give extra support if wind gusts hit the tunnel head on.

VENTING

If cross over ties are taut you can just lift sides and they stay up. However, high winds can shake the tunnel enough that the sides fall back down. We use scrap wood to hold up sides…2×4 lumber at 3’-4’ lengths propped up under the bunched up plastic will keep sides up. Could also use hardware clamps… just lift plastic up and clamp.

 

TIPS & NOTES

  • We used SDR 21 PVC, I would strongly recommend schedule 40 PVC instead. We had a rib crack on a windy day (before we improved our tunnel end design). That probably could have been avoided with a few extra dollars spent toward schedule 40 PVC.
  • Every single connection with couplers, tees…whatever must be secured using PVC cement, don’t skip that.
  • Save money by buying long lengths of rebar and cutting to size. We bought 20’ lengths and cut down using angle grinder.
  • We found it easiest to cut all cross over ties and tie them to the rebar before putting plastic on…that way it’s quick to throw the ties over as soon as plastic is in place.
  • If you can afford a metal structure with actual greenhouse plastic, do it! However, if you have very little money or are trying to farm debt free (like us) and doing what you can with what you have then this may be the design for you. I’m not going to sugar coat it…we’ve had issues with the wind…build at your own risk. But those issues were correctable and the structures are still standing. Thus far they’ve survived 50mph wind gusts but we still have to “babysit” them on windy days and cringe when the really strong gusts come through. The only goal with these structures is to make them last long enough so that we can make the money to invest in better structures next season. They’re a just a stepping stone, if you will.

How to Tighten Caterpillar Tunnel Cross Over Ties:

 

Erin says: We redid the ends inspired by design Curtis Stone recently showed in one of his videos, (shared at the bottom of this article). The tapered ends was needed due to some issues with wind and has worked very well, and you can see in the first photo that the ends were not yet tilted. We also added a smaller rib after the tilted rib to help keep the plastic taut and prevent it from flapping in the wind so much. A strong purlin with adjustable tension and crossover ties helped too.

(Erin says, “Don’t mind the weeds, lol!” 😏 )

Interior of tapered end of caterpillar tunnel.

 

This video was taken a few days ago during a wind advisory, we had sustained 30mph and up to 50mph wind gusts the entire day…and we made it through in one piece with both tunnels!

 

So far so good but I’ll say that I’m very much looking forward to “real” metal caterpillar tunnels next season. Erin used the 6 mil plastic. She said,  It will only last a season but long enough to make money to buy real greenhouse plastic next time.

You do what you gotta do to get where you want to be. Step by step, little by little.

 

Erin’s Caterpillar Tunnel Tips and Pics

A member of the Planting for Retirement Facebook group asked how Erin accesses her tunnels if both ends are tapered, and here’s her response.

Both ends of the caterpillar tunnels are tapered. Venting and entering the tunnels happens along the sides…pick a spot, lift up with your hand and place a clamp on the PVC to hold plastic up.

With tapered ends for better wind resistance, tunnel access is from any side location. Just roll up the cover and clamp it! Image by Liberty Heritage Gardens

 

Caterpillar tunnel
Caterpillar tunnels are easy to vent and expose to direct sunlight on mild days with a few well placed clamps. Image – Liberty Heritage Gardens

 

Caterpillar Tunnel planting time! Image by Liberty Heritage Gardens, LibertyHeritageGardens.com

 

Caterpillar tunnel greenhouse, high tunnel
Caterpillar tunnel – plants in the ground! Image by LibertyHeritageGardens.com

 

It’s Hard Work, But Good Work!

We decided not to crop this image from Erin, because it’s an example of the reality of farm life: hard work and long hours! But… uber rewarding. So if you’re just getting into it, be aware and prepared for a lot of hard work, but likely, the most rewarding work you’ve ever enjoyed doing for a living.

Farming is hard work, long hours but incredibly rewarding work.

 

caterpillar tunnel greenhouse, high tunnel greenhouse
Caterpillar tunnel seedlings. Farming is long hours, hard work but good work. Nothing like being your own boss and working with nature and growing things! Image – LibertyHeritageGardens.com

 

Here’s the caterpillar tunnel greenhouse construction video Erin mentions, by Curtis Stone, author of the popular bestselling book, The Urban Farmer.

 

Cattle Panel Tunnel Greenhouse

This is a really nice looking cattle panel tunnel! We just got our cattle panel trellis constructed with plans to cover it to extend the growing season in fall. What a great idea to utilize any extra materials for turning the trellis into a tunnel greenhouse!


For more on the family farm and Erin’s story, you may enjoy this article on GardensAll.com

Thanks to Contributor, Erin Southwood of Liberty Heritage Gardens for sharing her DIY Caterpillar Tunnels journey! Great work and congrats of digging in, planting and growing your dream, Erin!1)https://www.libertyheritagegardens.com/

 

Selling at Farmer's Market
Market gardeners, Erin Southwood and her partner and Mom, Jamie, of Liberty Heritage Gardens via LibertyHeritageGardens.com

This was awesome info, and THANKS for Erin for sharing with us!

BUT… if you don’t have the time or build your own, or have less space, here are other options available on Amazon. We’ve included best sellers as well as those that include free shipping with Amazon Prime as much as possible.


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