DIY Rooftop Urban Greenhouse

This instructable details the construction of a small hydroponic greenhouse system I built on my roof. The system consists of 3 100 lt boxes with 6 planters each, plus 2 19lt buckets with 7 plants each, but it can be easily scaled to accommodate any size of greenhouse.

I decided to make this greenhouse because I was very interested in hydroponics and I wanted a way to experiment while also producing considerable and varied ammounts of food, and as a demonstration of how urban gardening can be very productive with a very small space. On the roof of the building where I live, there are cyclonic mesh cages which correspond to each flat and are intended to dry clothes. I decided to repurpose mine as an urban greenhouse. On the big boxes I mainly planted tomatoes, lettuce and other herbs, and on the small buckets I mainly planted herbs such as mint, peppermint, cilantro and basil.

The system is designed so that it is as simple as possible to make, set up and maintain in an urban environment, and very productive! I am very impressed with the results and I never would have thought that such a small space can be so productive with so little work!

I hope this instructable inspires you and serves to pave the way for more people to begin producing their own food in urban areas as not only is it very productive and efficient, but the taste of the produce is much superior to supermarket food, and as fresh as can be!

A great addition to this greenhouse would be a Garden Tower 2!

For this project you will need;

• 3x 100lt plastic boxes.
• 18x plastic pots (6 for each box).
• 1x 3m aluminium profile.
• 5x standard 2x4 wood.
• a few thin strips of wood.
• 14x small plastic containers (recycled, 7 for each bucket).
• 2x 19lt buckets (Recycled, these are the standard paint buckets).
• 6m length of 6m wide Greenhouse plastic. (Make sure it has a UV coating, or it will degrade quickly).
• a small roll of annealed wire.
• 3x 120xm x 60cm metal grids.
• Vermiculite substrate.
• Hydroponic nutrients (I recommend Ultrasol for ease of use or FloraSeries for maximum control).

Because the greenhouse is atop my roof, a wooden deck is needed as a base in order to allow airflow and prevent humidity problems on the roof below. Additionally, this helps maintain the inside air fresh and prevent overheating.

For the deck I used 6x 2"x4" 120cm segments connected on the top with 15 strips of thinner wood. These are where you will stand, so the spacing must be small enough to step comfortably and safely! To join everything, I simply used a 3" nail on each node.

This is probably the most important step for the greenhouse. It might seem a little tricky but it is actually quite easy to do if you do it methodically.

First, you must measure the cage and cut the plastic to proper size, adding about 20cm all arround to ensure proper fit and closure. In my case, since the cage I was using measured 1.40m x 1.40m x 2.50m, I cut the plastic into a 6m x 2.60m strip and a 1.60m x 1.60m square.

The plastic is thin and can be torn if not fixed correctly so, in order to prevent this, I cut several lengths of thin wooden strips to hold the plastic on all edges from the inside.

To fix these in place, first position the plastic, then place a wooden strip on the corner from the inside of the plastic, and then secure the strip to the outlying cage with a few lengths of annealed wire piercing through the plastic and tightly tied around the other side. In order to prevent tearing, make sure the wire pulls the wooden strip tightly, such that the wood, and not the wire, holds the plastic.

Hydroponics simply means that the plants are grown in a medium which provides no nutrients to the plants, but allows them to soak their roots into a nutrient solution which provides all the nutrition the plant needs. This method of cultivation allows the nutrition of the plant to be properly controlled and adjusted, and allows the plant to absorb and take advantage of the nutrients as easily as possible, greatly boosting production and growth speed.

The hydroponic system I used is about the simplest it can possibly get. It consists of a water container which holds, suspended above the water, some smaller containers with an inert substrate (I used vermiculite, but it can also be perlite, coco coir or stonewool) and holes on the bottom. This container, in turn, holds the plants and allows the roots to grow down and reach the nutrient rich water solution. Even though it is not a necessity, a small air pump into the nutrient solution will greatly increase aeration and ease nutrient absorption.

For my greenhouse, I decided to build the system in 2 sizes; on 100lt boxes for big plants like tomatoes, and on 19lt buckets for small plants such as mint, basil and cilantro. This system works very well for it's simplicity and, in order to germinate the seeds, all you need to do is fill the containers a bit more so that the water reaches the substrate in the pots, which will absorb it and remain evenly moist. Afterwards, you only need to make sure the roots reach the water. Once set up and running, the system can be left unattended for periods of up to 2 weeks.

For each 6 planter box you will need;

• 1x 100lt box
• 6x plastic pot
• 1x 100cm aluminium profile.

To make the boxes first lay out the pots over the box lid and mark the center of each one. Then, drill a small hole on each mark and, using a dremel, cut a circle around it of the proper size. Next, you need to drill a ton of holes on the bottom of each pot, so that the roots can come out into the water. Finally, Add an aluminium reinforcement across the bottom of the lid to be able to support the weight of the plats, as we have greatly reduced it's strength.

This version of the system is basically the same as the larger one, but scaled down.

For each 7 plant bucket you will need;

• 1x 19lt bucket
• 7x small plastic containers (I recycled mine from some kirkland grapefruits)
• black paint (If your buckets are white)

Making the buckets is easier than the boxes, as the holes can be drilled directly and the lid does not need to be reinforced. To make them I first marked the center of each pot by using a compass, and then simply drilled each 3" hole with a 3" holesaw directly. To make the holes on the small containers I heated a 1/4" metal rod and melted the plastic. The only added step is that the buckets need to be painted black. This is very important! as it will prevent light from reaching the nutrient solution, which would cause algae to grow, depleting the solution of nutrients and making it rot.

Because of it's simplicity, this system is very easy to use and maintain. All you need to do is make sure the containers have enough water, and to add some nutrients when you refill them. I use Ultrasol nutrients, which come as a powder which is added at a rate of 0.5g/lt of water. If you want to have more control over the nutrition of your plants, you can switch to FloraSeries nutrients, which is a 3 part hydroponic nutrient system.

Normally, the containers need to be filled about halfway to thre quarters of the way up, but to get seeds started all you need to do is fill the containers up so that the water reaches the substrate in the pots. Because hydroponic substrates are very absorbant, the water will permeate up and keep it evenly moist, allowing the seeds to sprout.

Once the plants are growing, hang some metal grids from the top to provide support for the taller plants.

After just a few weeks, you will start having very abundant results! I managed to get about 1 kg of tomatoes a week, plus a few lettuce heads and several other herbs. I encourage you to experiment with other plants and share your results in the comments.

The system is designed so that it is as simple as possible to make, set up and maintain in an urban environment, and very productive! I am very impressed with the results and I never would have thought that such a small space can be so productive with so little work!

I hope this Instructable inspires you and serves to pave the way for more people to begin producing their own food in urban areas as not only is it very productive and efficient, but the taste of the produce is much superior to supermarket food, and as fresh as can be!

There is still much room for improvement so please let me know what you think and, if you have any suggestions and ideas drop them in the comments below.

I hope you liked the project and, if you consider it worthy, please vote for it on the gardening contest!

One amazing addition to this greenhouse would be a Garden Tower 2, as this would allow me to go organic and process my organic residues in-situ, creating a completely local food system.