How We Built a Greenhouse From 99% Salvaged Materials
- Kayla McCarthy
- Jul 19, 2023
- 4 min read
With plans in full swing to begin planting at Chainy-Stakes Farm in May 2022, the next step was establishing a place to propagate seeds. It was April 2022 when we finally got around to building the greenhouse. With a lot of help from my landlord William and another intern who was working with us at the time, plus a little nudge of assistance from Mother Nature, we were able to build this greenhouse from 99% salvaged materials.
Due to our location in the Chehalis River floodplain of Independence Valley, it floods reliably almost every winter. During the winter of 2022, the valley was hit with a massive flood. As happens during floods, various pieces of debris were swept up and washed from one farm to another down the valley. When the flood finally settled, it appeared that a large piece of greenhouse plastic floated onto William’s property. William had the foresight to save it for some young wannabe farmers who came along later that year… (one of which was me!) Although the valley was rampaged with catastrophic flooding that year, we were able to find a silver lining… Mother Nature was telling us that we needed to build a greenhouse!
After the fateful acquisition of this greenhouse plastic, we scavenged around the farm for other materials we could use. William had lots of ecology blocks (eco-blocks) left over from the days when he used to store silage at the dairy farm. We also found some old hog wire fencing. We figured we could use the eco-blocks to form two parallel greenhouse walls, and then use the hog wire to make an arch between the two walls. The tongues on top of the eco-blocks acted as an anchor point, so we could get some leverage to bend the hog wire into arches. Of course, we also double-secured the hog wire by tying it with bailing twine to the rebar lifting hooks on the eco-blocks. Bailing twine is a farmer’s best friend! With the walls and arch fully constructed, we could approximate how much plastic we needed, and we cut it to size. Next, we used a reciprocating saw to make a lengthwise incision into a salvaged ABS pipe, which we slid over the sharp edges of the hog wire at each end of the greenhouse to act as cushioning. That allowed the greenhouse fabric to slide right over the hog wire arch without getting snagged or torn.
To secure the greenhouse plastic and make it as airtight as possible, we folded the excess plastic around scrap pieces of wood and then used a cement drill to bolt the wood into the eco-blocks. The other intern constructed frames on both ends, which he eventually used to install doors. He did an excellent job of carefully folding the plastic around the ends and securing it to the frame in a way that would minimize any outside elements such as wind or rain from getting into the greenhouse.
With the plastic overtop and framework inside, it's starting to look more like a greenhouse! Photo taken April 17, 2022.
Finally, we made the inside more functional by building a frame with scrap lumber that would support the arch and provide some framework for installing shelves. We outfit some shelves from log slabs, which extended from the flat surface of the eco-blocks. We added a plastic folding table and some plastic shelving units, which we purchased for cheap from the local thrift store. Luckily there was already a water spigot behind the greenhouse, we just needed to extend the hose and affix it with a watering wand, and the greenhouse was fully functional! The only materials we purchased to build this greenhouse were cement bolts and plastic shelves, everything else was scavenged.
I was so inspired by our thriftiness after building the main greenhouse, that I decided to build a “hardening house” in a similar fashion. The “hardening house” is an area where seedlings go after growing up in the protective shelter of the greenhouse, to get conditioned to the atmosphere before they are transplanted. Hardening houses are still covered on top, but mostly open on the sides to allow more air circulation.
We similarly used eco-blocks to construct the base, except this base was set up in a U-shape since it didn’t need to be as big as the main greenhouse. To create the arch, I repurposed a picnic canopy, which was sadly blown over and broken during a storm after the last farm potluck. The legs of the canopy were bent and could not collapse, but it was near perfect for what I needed. I weaved PVC pipe through the square frame of the canopy to reinforce it and then used PVC 3-way connectors to fashion two cross beams running across the ceiling of the hardening house in an X-shape. I used zip ties to sinch the PVC pipes tighter to the canopy frame in many high-tension areas, to increase the structural integrity.
To secure the canopy, I wedged one side of it into the U-shape base that we created with the eco-blocks and used bailing twine to tie the canopy frame to the rebar lifting hooks on the eco-blocks. To anchor the other two canopy legs, I put them in 5-gallon buckets and filled the 5-gallon buckets with sand, which turned out to be very heavy, I wasn’t worried about the legs moving at all!
I padded the sharp corners of the canopy with bubble wrap and duct tape, threw a scrap of greenhouse plastic over top, and weighed it down on three sides with scrap wood and rocks. The front was propped open with bungee cords to allow for airflow. Shelves were built by positioning some upside-down watering troughs in the corners and laying scrap wood across the top.
We built the hardening house with 100% salvaged materials from around the farm, and I have to give credit to my Mom for helping me put it all together as she happened to be visiting me that day. Thanks, Mom!
Copyright, all rights reserved, 2023, Kayla McCarthy.
(Author's whereabouts upon publication: At an overseas military base, living it up on deployment).