I’ve had some requests for a write-up of this project. This is much smaller, and even easier and cheaper than my DIY easy carport greenhouse project. It’s faster to build, and probably won’t take more than a couple of hours to finish. Enjoy!
It’s a low-cost greenhouse that’s pretty easy to build, from free-sourced or cheap materials.
CHEAP WARNING!!! DON’T BE CHEAP LIKE ME!!!
I built it on top of some basic 4′ square raised beds. So we start with your basic raised beds (though you could do it with sunken garden beds). I salvaged the old wood from a carport demolition, and screwed them together with 3-inch screws.
After a few years the wood will rot and the screws won’t hold anymore. Then the bed will start breaking apart and spill all that nice soil you’ve been building.
So don’t do it the way I did.
Consider using a vertical corner 2×2″ to attach the boards, or metal corner brackets. Then get some ribs material. You could use PVC, electrical EMT conduit, rebar, or even bent saplings.
I used 1/2″ PVC electrical conduit because it’s thicker than potable water PVC. I thought it would be important to resist shattering when cold. Turns out I was right.
Oops…did I do that?
Joel Salatin of Polyface Farm tells a story about finding the wrong way to do something really well. They built a mobile chicken enclosure all out of PVC, about $2000 worth. It worked fine at first. But when it was below freezing and they tried to move it, it shattered into a million-ish pieces. I heard that story after I built the greenhouse, but let it serve as a warning to you.
You also need some 2-hole straps, that will fit tightly around the pipe. You should be able to find some 1/2 GRC or EMT straps that will look too small. Be careful, because 3/4″ will not be tight enough. If you want to wrap rubber tape or something else around the pipe, 3/4″ will work, but it’s up to you. Of course, you also need some good 2 1/2″ – 3″ screws, about 16 of them.
Sidenote: I used these materials because I could easily get them, and I used to use them quite a bit in a previous job. I bought the PVC and some of the straps, and already had some straps and the screws.
Step 1: Attach the pipe
So take a piece of PVC and screw it to the end of the raised bed with the two-hole straps vertically. You want the pipe pointing to the sky. Now, if you want you can heat and bend the PVC into the proper shape with a hotbox or torch. Or you can do what I did and bend the pipe over manually. Just don’t let go of it before you strap it down.
It will hurt, I promise.
Repeat the installation with a pipe on the opposite end of the same bed side, so that you have two flags like CB antennas. (“We got us a convoy!“).
Now decide whether you need to add another pipe or two for support. I did, but you may not want to. I put in two more, equidistant from the ends and each other. So there’s about 16 inches between the pipes.
Now secure the pipes on the other end. You should have something that looks like this, with 4 ribs.
Step 2: Attach cross brace
Now you need something to use as a cross-brace for the top, to keep an equal distance between the ribs. I used a scrap piece of 1″ water PVC, but you could use a 2×4 or rebar, if you had it handy.
TIME SAVER: Make sure the cross-brace is square with the bed and at the top (apex) of the ribs. You don’t want to have to move and re-secure the cross-brace (don’t ask me how I know).
I chose to put the cross-brace underneath, because I think it make more sense and won’t get int he way of whatever covering I used. It was secured with rebar tie-wire (also baling wire). Then I cut small grooves in it with a hacksaw to help the wire stay secured better at the ends of the cross-brace.
Now you’re (almost) done! You still need to skin it with something. I used thin painter’s plastic, and did a double layer to help control temperature swings. I also took some scrap wood and framed up a crude door, and used the same plastic to enclose the ends of the greenhouse. Unfortunately I did this project in 2 weekends (though it should only have taken one) and I took pictures on the first, but not the second.
Using this greenhouse, I had lettuce and spinach in March, that we could have a family salad from almost every day. When I opened the door it would nearly steam. Not too bad for a cheap DIY greenhouse.
I did a couple things to help with heat retention/cold mitigation. First, filling up gallon milk jugs with water and set them against the back wall. Also took a page from Growing Power in Milwaukee, and buried food scraps in rows against the front and back walls. The decomposition releases heat to help germination and plant growth, in addition to becoming good compost for the plants to grow in.
How did it last?
The beating summer sun wreaked havoc on the non-UV-protected plastic. It started to degrade, get brittle and break by July (about 8 months of use). The plastic I used cost about $5, so not too bad. It would have been better with real commercial greenhouse plastic. The problem is finding it in small enough quantities. I did find a supplier (online, of course) that I could buy twice as much as I needed. This was fine because I was planning on making another greenhouse anyway.
Then I decided to update the greenhouse covering. Instead of buying greenhouse plastic that lasts 4-7 years, I used 25-year corrugated clear polycarbonate panels to wrap over the ribs. I secured them to the panels by strapping 2×4 pieces to the ribs then screwing the panels to the 2x4s.
I did have some issues with the ribs not bending at the same radius along its length. But it wasn’t a problem until I put on the poly panels. That took some interesting adjustments to make it come out right, but it worked.
If you have any questions about this greenhouse or anything permaculture, please comment below and let me know.
I’d love to talk to you!
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The Crew at TPL