Building the Container of Dreams Pt.4

(Extracts from my PhD Thesis) 
This series of posts provides a step-by-step description of the construction and conversion processes involved in building the Container of Dreams. They outline my studio investigations and experimentation and document both accomplishments and failures experienced throughout the project. This is Part 4.

Part 4:
Western and End Exterior Walls

The western and end exterior walls of the container have been dressed in plastic drainage cell, generously donated to the project by Ausdrain. Drainage cell is a black plastic product manufactured for use as a horizontal drainage application for roof gardens, planter boxes, green roofs, paving and sporting fields. This application of drainage cell as an exterior finishing for buildings is a completely new and innovative way of utilising this product. 

Mounting the drainage cell over the wallboard

I first thought about using drainage cells in this manner after watching an episode of Grand Designs Australia. In this episode the builders were installing a grow wall in a house that was being constructed. The grow wall product being used in the build in this episode was specifically designed and manufactured for this purpose and was large, cumbersome and moderately expensive. I thought that it had an interesting aesthetic quality on its own, before growing medium, or potting mix, and plants were placed into it, and I began to contemplate how I might incorporate a comparable aesthetic into my project. This prompted me to look into alternatives, both lighter, in terms of weight capacity for the structure, and cheaper, to improve affordable aspects of my project. While conducting an online search I discovered drainage cell and conceived the idea to employ the product as exterior wall cladding. I then approached Ausdrain to support the project. The implications for the alternative application of this product are significant and could generate opportunities for potential future market expansion for the company. Ausdrain happily agreed to supply sufficient product to cover the exterior of the container and were impressed with the outcome of the repurposing of their product. Gerard Jorna, the CEO of Ausdrain, commented on our Container of Dreams Instagram page with a “Wow!” and thanked me for showcasing their product in a new way.

​The drainage cell is fabricated into 500mm by 500mm interlocking panels which made the installation process very simple. These panels were straightforward to mount and fastened into place using galvanised screws secured through the pre-set fixing holes in the cell panels. Simple cutting with a hand saw trimmed the excess at the wall ends. 

Container exterior showing completed drainage cell installation

Grow Wall Experiments

I have done various testing and experimentation into additional uses of the plastic drainage cell. As indicated I had always intended to use the product in an alternative manner to the one for which it is designed. My trials were related to supplementary treatment on the exterior surface of the container, in this instance their effective application as a grow wall or green wall.

I trialled two different approaches for this experiment. One was to use the drainage cells in a horizontal configuration and the other was to assemble the cells in a vertical arrangement. Both investigations were conducted in unison to establish the best format to apply to the construction of the container itself. My rationale for conducting the two research methods was to determine whether it was preferable to establish the plants in the cells first and then attach to the container or whether it was easier to fix the empty cells on to the exterior and then plant out.

I wanted to use edible species of plants for my initial trials to add an element of self-sufficiency to the project to enhance its sustainable aspects. Consequently, I elected to use common garden mint and strawberries for these preliminary experiments. These were chosen for their growing qualities and their root systems. Mint has an extensive spreading root system and I considered this would assist in keeping the growing medium in place in the cells. Strawberries are shallow rooted and have a trailing root system. They are easily grown in vertical arrangements.

The first trial was to lay the drainage cell horizontally, or flat, to allow the growing medium and plants to establish before lifting cells into their vertical position. Part one of this process, the horizontal arrangement, was considered successful. Two single cells were used in this experiment and were not connected to one another. The growing medium chosen was a high quality potting mix and the plant selected was common garden mint. 

The second method of experimentation was to fix the drainage cell into a vertical position prior to the application of any additional substances. This was considered to be the preferred technique due to the processes required in the construction phase of the container home.
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Cells were fixed to a temporary vertical wall, in this instance, a wooden pallet, using galvanised screws and then filled with potting mix. The addition of straw was required to aid the potting mix to remain in place and assist with moisture retention and release of nutrients. Coconut husk, known as coir, was also considered as an alternative growing medium. Builder’s film was used to protect the surface of the wooden wall from any damage arising from moisture. Strawberries were selected for the trial of this method and the planting of strawberry seedlings for this testing is pictured in the Image below.

Planting strawberry seedlings into prepared drainage cell

Both experiment types were very consuming of both time and resources. They both necessitated daily watering, although the vertical trial required much more water than its horizontal counterpart. This was believed to be due, in part, to the size of the drainage cell used. The cells used are only 30mm deep which exposed their limitations for their capacity to retain moisture. The vertical configuration meant that moisture drained away faster due to the forces of gravity than it did in the horizontal rendering.

In the summer of 2016 and 2017 a heatwave hit. It was categorised as the hottest Australian Summer on record at the time (Australian Government Bureau of Meteorology 2017). The place where I reside in Northern New South Wales experienced several consecutive days where the temperature regularly reached 48 and forty-nine 49 degrees Celsius over the months of December 2016 and January/February 2017. These dangerous conditions even saw temperatures reaching 50 Celsius on a couple of occasions. This extreme weather event had critical consequences for the Container of Dreams project, and this green wall experiment was one of the first casualties.
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The trials failed. The plants died in the extreme heat. I was unable to maintain sufficient water to preserve them and they literally fried in the high temperatures. Nevertheless, I concluded that while the experiment itself failed due to lack of moisture, the concept could still have been successful with some minor alterations.

Had the drainage cell been that of 50mm in depth, instead of the 30mm type which were used in my research, the plants would have had an improved prospect of survival. However this would have resulted in much greater weight being placed on the supporting structure of the container and would need to be considered in the construction phase. The use of steel for exterior framing would offset this problem.

After the breakdown of these investigations I concluded that I would not integrate the green wall component into my construction. I made this evaluation after reflecting on the findings of the experiments. It was a major undertaking to retrofit the container to enable it to support such weights as would be required by a grow wall. This would add considerable expense to an already restricted budget and one that was not practicable under the conditions of the project. However, that is not to say that it cannot be done, just not under the parameters of this particular project. I concluded that I had initially investigated the drainage cell as a wall dressing because of its aesthetic attributes and I was more than satisfied with the outcome of that exploration.

I hope you are enjoying my weekly series of the building processes undertaken during my research. Next week I will present the treatment methods and process used for the exterior of the Eastern Wall. Stay tuned...