Terracing and the Green Machine
Making meaningful green spaces in high places
This article is part of a series that compose the main verticality narrative. The full series is located here.
The Hanging Gardens of Babylon, one of the Seven Wonders of the Ancient World, and possibly our first major attempt at linking our high places with greenery and vegetation. Image source.
Two things that every human being needs are to escape the surface of the earth through verticality, and to be around plants and vegetation. Ever since the beginnings of permanent shelter and architecture, humans have been attempting to escape the surface of the earth by creating and inhabiting high places. We’ve also been repeatedly trying to recreate the experience of the surface by linking these spaces with greenery. Take the Hanging Gardens of Babylon for example. It was most likely built in the 6th century BC and is considered one of the seven wonders of the ancient world. It also represents one of the first attempts by humanity to link our high places with the experience of the surface through the inclusion of plants and vegetation. There is little evidence of this building actually existing today, but the idea of creating high places with vegetation and green space was so profound that written accounts of the building have survived, and throughout time many artists have created representations of how the building may have looked.
Torre Guinigi in Lucca, Italy. An early example of incorporating greenery high above the surface. Drawing by Minty Sainsbury. Image source.
Another early example is Torre Guinigi in Lucca, Italy from the late 14th century. The tower was most likely built by a wealthy family as a symbol of status and for defense, but just having a high place to occupy wasn’t enough for them. They went a step further by planting a group of Holm Oak trees on the roof. This was a deliberate attempt to recreate the experience of the surface in the sky. No doubt it took extra effort and cost to plant and maintain this roof garden, and the fact that it still exists today is a testament to the timelessness of the idea.
Human beings are surface dwellers. Ever since our ancestors descended from the trees and out onto the savannah, every one of us has lived a surface-based existence. The surface is where we get our food from, where all our buildings are anchored to, and where nearly all human movement and recreation occur. It is where the action happens, and because of this when we build and inhabit high places we often attempt to recreate the experience of the surface in the sky.
Unfortunately, for all our attempts to recreate the surface in the sky, it’s an impossible feat. There is only one surface, and this is why it’s where all the action is. Oh, do we try though; the history of architecture and urban planning is full of attempts to separate out or recreate part of the surface experience in high places. In their 1927 film Metropolis, Fritz Lang and Erich Kettelhut imagined a future city with sky bridges and a multi-layered surface experience. Around the same time in 1930, Le Corbusier’s unbuilt Ville Radieuse (The Radiant City) separated fast-moving street traffic in favor of open space and pedestrian activity at ground level. A couple decades later, Peter and Alison Smithson famously attempted their ‘streets in the sky’ concept by lifting the pedestrian experience up above the ground and into their buildings. Numerous other examples of concepts for ‘the city of the future’ throughout the 20th century include a separation of city functions, usually by burying unsightly or fast-moving traffic below a more human-friendly surface experience. In the rare cases where these concepts are actually built, they never fully recreate the surface experience in the sky, and are not as successful as the architect imagined; The Smithson’s Robin Hood Gardens, built with their ‘streets in the sky’ had problems with vandalism since opening, and was recently demolished after falling into disrepair.[1]
Left: Harvey Wily Corbett's City of the Future from 1913. Right: Le Corbusier's Ville Radieuse (Radient City) proposal from 1930. Each of these drawings depicts a vertical separation of the city's surface functions, effectively reducing the vibrancy and activity of the actual surface.
So what can we do to make our high places more meaningful and pleasant? We can't recreate the surface, but we can do a few things that would make these spaces more successful. Greenery is found throughout the natural environment and we are drawn to it. It represents life. We utilize parks and natural landscapes to escape the modern urban existence and to recharge our minds. Proximity to plants on a regular basis makes us happier, reduces stress levels, and can increase productivity and reaction time.[2] Plants also clean our air and remove VOCs from our environment.[3] We need to be around plants, and we’re happier and healthier when we are.
Architects and designers understand this link, but very few of them are properly trained to integrate vegetation into their spaces. This lack of training leads architects to ‘greenwash’ their projects, meaning any rooftop, terrace, or unprogrammed space gets rendered with trees and vegetation in an attempt to make spaces more inviting or more ‘human’. On balance, this is a good thing. Green space is great when it’s included in and around our buildings, but in reality, properly integrated green spaces require much more design, upkeep and physical space than greenwashing would suggest. This is a job for landscape architects, and when done properly it also requires an involved and invested client.
Another crutch of architects is to draw vegetation as a lush, overgrowing jungle of tropical plants and trees with crowds of people enjoying them. These utopian visions are often presented regardless of a project’s location or climate. Most climates on earth don’t support this type of vegetation, and many are either too hot or too cold for people to use the spaces with regularity. Solutions based on informed design decisions that consider local climate and human behavior are crucial to the success of greenery in our high spaces. This includes properly sized, dedicated space for root balls, and space for vegetation that is deeper and more integrated than a single box for each plant. This also includes green spaces that work as part of a larger design narrative rather than applying a green pastiche after the building has been designed.
Fear not, however: the good news is that many world-class architects already work to create meaningful green spaces throughout their projects. Also, I should mention that some green space is almost always better than no green space, so architects who make it a point to include green space in their designs should be commended. I should also mention that I’m a big fan of each of the architects and buildings discussed below, and I regard them all as near the top of the industry; the following commentary is not meant to denigrate these excellent buildings, but merely to point out a few ways to get the most out of our green spaces in the sky. Let’s jump in.
First, plants should grow from foot-level. This seemingly simple concept is all too often avoided due to the space required below floor-level for soil, root and drainage infrastructure. The common solution is to raise the soil above foot-level and into planters. This creates three issues. First, planters create a manufactured-feeling, putting the plants 'on display'. Second, they result in a disconnection between human and vegetation. With planters, the surface you walk on is not the surface the plants grow on. Third, planters restrict human movement. Parks and natural landscapes all have plants growing from the ground, meaning you could walk off the path and onto the green space if you so choose.
Norman Foster's Commerzbank Tower in Germany, completed in 1997. The sky gardens utilize vegetation in planters, creating a disconnect between human and plant. Image © Die Bitumenbahn. Image source.
David Chipperfield's Amorepacific Headquarters in South Korea, completed in 2017. The vegetation is planted at foot level, making it more accessible and integrated into the experience, much like natural vegetation. Image © Noshe. Image source.
Take a look at these two examples, both from world class architects. First is Norman Foster’s Commerzbank Tower in Germany, completed in 1997, and second is David Chipperfield’s Amorepacific Headquarters from South Korea, completed in 2017. In Foster’s design, he uses the planter strategy, resulting in raised beds of planting and a disconnection between human and vegetation. In the Chipperfield example, the plants grow from foot-level, resulting in a much deeper connection between human and vegetation. Much like a park or natural landscape, you could walk onto it if you wanted. In fact, it would be easy to confuse this high space with a ground-floor space, mainly because of the trees growing at foot-level.
A look at the contrasting building sections (pictured below) tells a deeper story. In Foster’s design, everything occurs above the floor slab; this is much easier and cheaper to build, which is why it’s so common. Contrast this to Chipperfield’s section, in which the entire level below is given over to the soil bed infrastructure. This requires more investment by the design team and more money from the client, but results in a much more meaningful human-to-plant experience.
Partial section through Foster's Commerzbank Tower. All the plantings exist above the floor slab, which is less expensive, but comes at the cost of isolation. Image © Foster + Partners. Image source.
Partial section through Chipperfield's Amorepacific Headquarters. The plantings grow from foot-level, requiring the soil and drainage infrastructure to take up space on the floor below. This requires more design integration and cost, but results in a much more immersive experience. Image © David Chipperfield Architects. Image source.
Second, Include vegetation you can be under. This means trees large enough to have a canopy you can be under. People love to sit under trees; the light quality is better, they’re cooler and they feel protected by the canopy.[4] Humans also have a deep, primal connection to trees, since our ancestors once resided in them before descending down from them and out onto the savannah. Think about it: any street experience is made better with trees, and parks are much more inviting when you can sit or stroll under a canopy of trees.
Tree root structure. On the left is what people typically think a tree root system looks like, with a structure similar to the canopy. In reality, it's much more like the drawing on the right, with a shallow but broad structure, which maximizes the amount of nutrients the roots can gather from the soil.
Third, group together many plants; don’t isolate them from one another. Many projects that include planters tend to isolate trees and plants from one another, effectively rendering them ‘on display’ rather than an integrated, immersive part of the experience, and they don’t recreate the surface experience. Isolated planters also rarely provide enough space for a tree’s root system to properly function.
WOHA's Oasia Hotel in Singapore, completed in 2016. The gardens here are large and include trees, providing a pleasant canopy to be under as well as a large space for vegetation to grow together. Image © Patrick Bingham-Hall. Image source.
Instead, green spaces should be designed big enough for a grouping of trees and plants, which is how they exist in the natural landscape. An excellent example of this strategy is WOHA’s Oasia Hotel in Singapore and completed in 2016. The greenery surrounding the pictured terrace is integrated together and growing from foot-level, making the space much more effective and comfortable to be in.
Vo Trong Nghia's FPT University Building, completed in 2017. The balcony trees are singular elements, effectively rendering them as 'on display' rather than integrated into a larger garden. Image © Hiroyuki Oki. Image source.
Contrast this strategy with the singular, isolated trees of Vo Trong Nghia’s FPT University Building in Vietnam, completed in 2017. Each balcony gets a single tree, which results in them being ‘on display’ rather than part of a larger garden. This is an abstraction of the natural world, and is not as immersive or meaningful as WOHA’s strategy in Singapore.
Section through WOHA's Oasia Hotel in Singapore, completed in 2016. All the elements discussed here come together into a series of green spaces in the sky that provide immersive experiences for the people using them. This is no doubt the result of an informed design process and an invested client. Image © WOHA. Image source.
In conclusion, humans have been linking their high places with plants and vegetation since the beginnings of architecture and shelter, and we’ve been continually trying to solve the problem of recreating the surface in the sky to this day. A true recreation may be impossible, but we’ve explored a few strategies here that can help to make these spaces more meaningful. After all, humanity will most likely never stop trying to escape the surface of the earth, but with each attempt we should keep striving to create meaningful experiences with greenery in our high places.
Check out other posts about architecture and verticality here.
[1]: To be fair, the story of Robin Hood Gardens is complex and multi-faceted, and the 'streets in the sky' concept wasn't the only factor in its eventual demise. It was indeed a factor, however, which is why I use the example here.
[2]: Grinde, Bjørn, and Grete Grindal Patil. “Biophilia: Does Visual Contact with Nature Impact on Health and Well-Being?” International Journal of Environmental Research and Public Health 6 (2009): 2332-2343. Jumeno, Desto, and Hiroshi Matsumoto. "The Effects of Indoor Foliage Plants on Perceived Air Quality, Mood, Attention, and Productivity." Journal of Civil Engineering and Architecture Research 3, no. 4 (2016): 1359-370. Keniger, Lucy E., and Kevin J. Gaston, Katherine N. Irvine, Richard A. Fuller. “What are the Benefits of Interacting with Nature?” International Journal of Environmental Research and Public Health 10 (2013): 913-935.
[3]: NASA. "Plants Clean Air and Water for Indoor Environments." NASA Spinoff. Available at https://spinoff.nasa.gov/.
[4]: Whyte, William H. The Social Life of Small Urban Spaces. New York: Project for Public Spaces, 2001. 46-47.