Make a Tunnel Greenhouse From Old Trampolines

When we stumbled upon our old trampolines, remnants of our children's younger days, my wife had an ingenious idea: why not repurpose them to build a greenhouse? Initially skeptical, I decided to give it a try, and it turned out to be a fantastic and cost-effective project. Armed with a stick welder (a budget-friendly inverter welder from Lidl), I set out to transform the trampoline frames. However, rest assured that this project can be accomplished using a drill and some bolts. There is a wealth of discarded trampolines out there, waiting to be recycled, and their sturdy frames often outlast the trampoline fabric, making them perfect for repurposing.

The pipes have holes for the springs, use the springs as hooks to hang things or plant support.

Supplies

You will need the following materials and tools for this project:

Trampolines: Allocate 1/2 of a trampoline per bow. For my greenhouse, I utilized five bows, resulting in an approximate length of 6.3 meters.
Bolts, Nuts, and Washers: Obtain an ample supply of these fasteners.
Welder: Any welder capable of handling galvanized iron pipes can be used for this task. However, note that welding is optional.
Rebar: Procure some pieces of rebar and bend them into an L shape.
Angle Grinder: Equip yourself with an angle grinder, along with cutting and grinding disks. Flap disks with sandpaper flaps work effectively as well. Alternatively, a hacksaw or a sawzall can be used.
Zip-ties: Have an adequate number of zip-ties on hand.
Greenhouse Plastic: Acquire high-quality, age-resistant, and UV-safe greenhouse plastic or construction plastic. You can find suitable options at your local Dollarstore.
Tape: Use weather-resistant and UV-resistant tape with strong adhesive properties. Construction tape specifically designed for construction plastic is recommended, even though it may be costly. This type of tape ensures durable joints that can withstand various weather conditions.
Pressure Treated Wood: Obtain 22mm x 95mm pressure-treated wood for the inside ridge of the greenhouse.
Hinges: Procure hinges for the door.

Optional: Consider using gray zinc spray to cover the welds and prevent rusting.

By gathering these materials and tools, you will be well-prepared to construct your greenhouse.

Step 1: Making the Footers

To begin, determine the desired length of your greenhouse. In my case, I constructed a greenhouse using five bows made from three trampolines. If you require a longer greenhouse, simply obtain additional trampolines.

Commence by welding the bottom feet-pipes together. Each trampoline consists of four pieces that rest on the ground. At each joint, ensure to remove the top section of one of the sides to prevent obstruction for the bow. Alternatively, you can use a few bolts to securely fasten the parts together.

Repeat this process to create two identical structures, one for each side of the greenhouse.

Step 2: Making the Bows

Next, proceed with constructing the bows for the greenhouse. Each trampoline's circle consists of 8 pieces, so you will require 4 pieces for each bow.

Additionally, there are 8 straight pipes that connect the circle to the feet of the trampoline. For my setup, I used one pipe on each end of the bow to provide some extra height. When attaching these pipes, ensure to trim a section from one side, it obstructs the fitting over the footing. It's worth noting that all the pipes have a narrower side that fits into the wider side.

To join the pipes together, you have a few options. You can either tack weld them or use bolts. Self-drilling screws can also be utilized. It's even possible to leave them without any bolts or welds, depending on your preference.

Additionally, four of the bow pieces come with mounting pipes for the footers. However, I removed them using an angle grinder. This step is not necessary, but it can simplify the assembly process.

With these instructions, you'll be able to construct the bows and assemble the greenhouse effectively.

Step 3: Mounting the Bows

Next, it's time to join the bows and footers of the greenhouse. This step should be relatively straightforward. Begin by determining the desired width of your greenhouse. You can adjust the width by fastening one side of the footer and pulling on the other side. To secure the footers in place, you can use L-shaped rebar. Pound the bent part of the rebar into the ground to hold the footer down. Make sure to measure and cross-measure to ensure the greenhouse is fairly straight. For added stability, use more rebar to secure the footers firmly.

To further stabilize the bows, I recommend welding tabs onto the center of each bow. These tabs will allow you to mount a pressure-treated board. While this step is optional, it helps enhance the stability of the bows. However, it's possible that the greenhouse will still function adequately without this addition.

By following these guidelines, you'll be able to effectively join the bows and footers, ensuring a sturdy and straight greenhouse structure.

Step 4: The Doorway

Additionally, let's cover the construction of the doorway for your greenhouse. Here's how you can create a functional doorway:

Find suitable pipes for the doorway, which can be sourced from a yard sale or any other available materials.
Utilize thinner pipes to construct the door frame, making use of the trampoline security net to form the door itself.
Attach a couple of hinges to both the door and the doorway. Welding the hinges securely is one option, but alternatively, you can use wood to create the doorway and attach the hinges to it.
If you prefer a simpler approach, you can construct the doorway entirely out of wood. This involves building a wooden frame and using appropriate hardware to attach the hinges for the door.

By following these instructions, you'll create a functional doorway for your greenhouse using either pipes or wood, depending on your preference and the materials available to you.

Step 5: Covering the Greenhouse

Now let's move on to covering the greenhouse with the greenhouse tarp. If you have a 4 x 8-meter tarp, follow these steps:

Begin by centering the first tarp and aligning it with the first bow of the greenhouse structure.
Secure the tarp in place using zip-ties and construction tape along the bow, ensuring it is stretched correctly to avoid sagging.
Join the two tarps together using tape where they meet.
For the end of the greenhouse, cut the tarp as needed to fit and securely tape it onto the bow.
In case the last tarp is too small to cover one of the short sides, cut it into pieces and join them together using tape.
Make sure to cover the door area as well, using the tarp.
For the backside of the greenhouse, you can use construction plastic and secure it with more tape.
Finally, to weigh down the tarp and keep it in place, put some sand or dirt on the bottom of the tarp.

By following these instructions, you'll effectively cover the greenhouse structure with the greenhouse tarp, ensuring a proper and secure enclosure for your plants.