Have you thought about building a vegetable rooftop garden with Alpha Blocks (YTONG block)? It’s a simple construction and it has a low cost.
For the construction of the garden, we use alpha blocks because they are lightweight and do not stress our building with their weight and we can build it in the dimensions we want. For example, with 14 pieces of alpha blocks we make a garden of 2.40 * 1.80 m or 4.32m2 and with a height of half a meter (0.60m * 4 = 2.40m, 0.60m * 3 = 1.80m)
In my example, I chose a corner spot for cost reasons. In the case of free space, we could make a complete parallelogram, so we would need twice as many alpha blocks pieces.
Instructions for building a rooftop garden with alpha blocks
1) Prepare the special glue and glue the alpha blocks (Ytong blocks) in a row, taking care to put glue on the bottom as well so that they stick to the roof floor and minimize the possibility of water running underneath. We place a second row of alpha blocks, on top, gluing them in the same way.
2) Calculating the soaking of the roof (they usually have a soaking towards the gutter), we drill holes on the side facing the gutter and place the pipe pieces in such a way that they protrude 2-3 cm on both sides (inside and outside of our garden). It is important that the pipes touch the floor of the terrace so that as little water as possible stays inside our garden. We fill the gaps with putty, keeping in mind that these are the places where the wear and tear will start over time.
There are two ways to open up the holes for the pipes (I should point out that alpha block is very easy to cut with a simple hand saw):
- at first by cutting the alpha block piece with a simple hand saw before gluing it, depending on the cross-section of the pipe,
- after the wall has been set up, using an electric drill and drilling successive holes (see diagram)
3) After the glue has dried, prime the alpha block, the roof floor and the mantra section inside and out up to the height of the alpha block and allow to dry.
4) Stack with care especially at the joints with the mantra and the roof and in those places where there are gaps of more than one to two millimeters.
With a piece of shower paper, sand to smooth the surfaces. After dusting thoroughly, go over with a hand of primer, if desired, and allow to dry.
5) Then with a large brush we go over the same areas with the insulator, making sure to dilute it first by adding water in the proportions given by the manufacturer.
The next day we apply a second coat of insulator.
CAUTION: All these operations must be done after making sure it will not rain in the next 24 hours.
6) Finally we paint with exterior paint.
How much soil will we need?
7) The next day we can fill with soil after putting gravel only where the drainage pipes are located, covering them to get good drainage without soil coming out.
Now to calculate how much soil we will need we calculate the sides of our garden. That is, if we have used 4 pieces of alpha block for one side, and 3 pieces for the second side then we have: 4 * 0.60m = 2.40m, 3 * 0.60m = 1.80m, 2.40m * 1.80m = 4.32m2.
The height of each alpha block is 0.25m. We, in the example, have put two rows, so the height of the wall is 0.50m. The soil is good to reach a height of 0.40m, so we have: 4.32m2 * 0.40m = 1.728m3 (cubic meters) of soil or 1.728 liters of soil or 35 bags of 50 liters. If each bag costs us 4 Euro, then the soil will cost us: 35 * 4€ = 140€
The soil I used is soil for outdoor plants.
What can we plant in the garden on the terrace?
8) If we take the example of Elias’s 1 m2 garden, which is a cheap and easy solution, we can plant: Radishes, carrots, parsley, beets, dill, rocket and many more. Imagine what the 4 m2 garden can hold.
It also has the following advantage, you can plant tomatoes, eggplant, melons and general plants that need depth.
Thanks to Greek Infographic designer Notis Rigas, for the text and the graph!