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Did you know that the environmental impacts of concrete are out of control and that the worldwide consumption of concrete is on its way to being four times greater in 2050 than it was in 1990? Did you also know that concrete is the most widely used material on earth?
Concrete is made primarily from cement, which is derived from calcium-rich materials like limestone or chalk, crushed up and mixed with clay or fly ash, heated to a high temperature and then ground into a fine powder which we know as cement. Cement, when mixed with water, sand and gravel, forms a paste which coats the sand and gravel particles, and then a chemical reaction called hydration hardens the mix into a single mass known as concrete. CO2 is released both from the energy used to fire the limestone, as well as in the chemical reaction as it forms concrete.
The first law of thermodynamics shows us that energy production needs to be curbed if we believe the law of conversion of energy. Energy can be transformed from one form to another, but is unable to be created or destroyed. In other words, without access to an external energy source, there is not an unlimited amount of energy available.
We are currently using the available energy at a rapid pace. It cannot continue. Fossil fuels are definitely a problem, but so is concrete production. Cement manufacturing is highly energy– and -emissions intensive because of the extreme heat required to produce it. It also releases a significant amount of CO2, about 5% of man-made global emissions. Its key ingredients – limestone, clay, gravel and sand are all mined, and are finite resources.
Concrete is used throughout the building industry for homes and commercial premises. It is the most widely used building material because of its strength in many situations. As landscape designers and garden-makers we need to stop and think – is its use in gardens appropriate? Or necessary? And what are we contributing to a global problem of depletion of finite resources and increasing CO2 emissions?
If retaining walls are required, in my area, cypress pine is a wonderful product sold as sleepers, as an alternative to rendered concrete retaining walls or garden boxes. Its longevity is around 100 years I have been told and it is naturally termite resistant so has none of the toxins as does treated pine. These sleepers can then be used as a retaining wall. Old fashioned? Is there a problem with this, if it is in sync with nature?
There is, in my opinion, no place for concrete. I don’t need to use concrete in my designs, because I work with nature and use what is naturally occurring.
Reused cypress timber palisade-style retaining wall. Design Fiona Brockhoff
The continuous use of concrete is strongly out of step with of a normal, sustainable garden – it is not clever garden design; it increases the project cost considerably and it is unnecessary, especially considering the environmental impacts. And this style of landscape design by most, but not all, landscape architects and landscape designers is becoming the norm.
Rendered walls used to create raised vegie beds
Clients are asking for gardens with raised garden beds, usually rendered concrete, on flat sites, which is a worry. People need to be made aware of the negative impacts of this extensive and unnecessary use of concrete and stop requesting it; they also need to use landscape architects and landscape designers who are aware of environmentally sensitive issues.
According to the Concise Oxford Dictionary, a ‘garden’ is:
‘a piece of ground devoted to growing flowers, fruit or vegetables’.
There is no mention of rendered, raised planter boxes or concrete en masse. A garden is about plants.
Working as a landscape designer I know that there are so many more sustainable alternatives to concrete – its just a matter of changing direction and taking the client with you. If you have a passion, and confidence in what you are talking about, the client will respect the advice when sustainable alternatives are suggested and why.
We all really need to start becoming more aware of the excessive use of concrete. And it is excessive. We need to start the conversation with others about this worldwide problem – it has to stop. We are all now fully aware of the impacts of fossil fuels, with the exception of those who lack any capacity for common-sense, so we need to make the world more aware of the effects of concrete. It is a major global problem that needs addressing now.
very good point Alison, added to which the excessive use of concrete is contributing to (causing!) the heat island effect and in a garden makes our gardens hotter places. Not to mention the concrete industry is also a very large user of water, which came to light during severe water restrictions a few years ago. We can certainly do better in our gardens, your upright timber sleeper retaining wall looks so much better than any concrete alternative!
Yes Kate, you are correct about the added heat effect. Concrete significantly increases ambient temperatures. And the amount of water that is used, and wasted with concrete, is mind-boggling. Thank you for your comments. Alison
Thank you for this article. Even though I was aware of the environmental impacts of concrete I wasn’t aware of the extent. I am known to use concrete in some of my gardens. In my head I justify this because it is hard wearing, long lasting and it can be recycled. I use it in high traffic areas and never just because it “looks good” I hate superficial use of any material and think it is a waste and poor design. My gardens are also full of plants so there is a balance between hard and soft landscaping leaning toward soft and until now I didn’t consider that I was overusing concrete. From now on I will look into alternatives and try to resist it’s use.
Unfortunately I am a bit of a lover of Brutalist Architecture and I am drawn to concrete and find beauty in its strength – I also love cypress pine so I guess I’ll just need to focus my love there.
From an equally Brutalist Architectural lover Stephen, we don’t want our gardens to all be built from cypress pine. I do have an issue with the ‘organic looking’ aesthetic and the constraints thereof.
I did see a lovely driveway today, (how do I post a photo?) recycled concrete, random paving, mid century architecture.
If the preference is for geometry as an expression of modern architecture, it can be very limited for us designers if the budget doesn’t conform.
I also am a designer, Rae, who specialises in sustainable landscapes. My designs and landscaping are significantly cheaper to implement because I don’t use concrete or other hard landscaping. My gardens are about looking at the site holistically, and managing the site with minimal disruption. I use aggregates instead of materials that require expensive drainage systems to remove excessive runoff from hard landscaping, often with this water going straight into the storm-water systems.
I wasn’t aware, Stephen of the vast use of concrete until I started doing some research. Much of the problem lies in the fact that it is used so extensively in commercial premises world-wide, and has now become an accepted product for external use with both commercial and domestic because of its ease of use.
But there are so many environmental ramifications about the external use, that this is why I have chosen to highlight the negative impacts of concrete use.
I prefer to work with consideration of environmental impacts at all times. And I believe that it is our duty, as landscape designers, to be cognisant of these environmental issues when we design gardens for our clients.
I also like the clean lines of concrete. But I figure that the environment is more important to us.
Does anyone have a suggestion other than paving for a narrow treed area at the back of the house, not much sun but funnily enough plenty of weeds?
Compacted decomposed granite would work, and around 100mm thick should be enough for pedestrian traffic. It will pack down harder if you do it in 2 layers and add a finer material such as cement dust or lime, which will also deter weed growth but it will still allow water to penetrate. If the weeds are of the really pernicious type, you can also install weed mat underneath the deco granite.
Thanks so much, i will follow your advice and save the planet a tiny bit!
Thank you for your article, Alison. The stark truth about concrete needs to be more widely known (I didn’t know!)
Thank you Judi for your comment. It was only when I started doing research that I realised how environmentally bad concrete is. There are some who wont change their ideas about concrete use. But I believe that industry leaders will see the need for change; the devastating impact from unregulated use cannot continue indefinitely.
Great article and a reminder to all landscaper designers that concrete is a material that we need to use less. So I often you hear designers talking about the plants softening the edges of the hard, usually concrete, lines.
We also need to be reminded that it is the production of concrete, not the use of it that is unsustainable.
Hi Dianne
Thank you for your comments.
I do have a minor argument about the use of concrete not being unsustainable [sorry double negative so may be hard to understand!]. My issue would be that laying concrete is labour intensive. You need concrete trucks to take the wet cement to the site, then a labour force to spread this wet material. There is also the preliminary boxing of the areas to receive the wet concrete. So this labour is also using energy. If you consider that energy is finite, then this means that the use of concrete would theoretically be unsustainable.
Thanks Alison, your post is really eye opening. Recently i have also build retaining wall using Treated pine, that really gives color to the backyard, while the cemented retaining wall looks cold.
I have to do paving in my driveway and perimeter along house, do you have better solution. Apart from that i am also planning of having fruit trees around my house and planning to steel poles to make espalier, do you think i should use Pine poles.
Hello Arun
As a strongly principled sustainable landscape designer, I do not use paving. I find much more aesthetically appealing is the use of aggregate, especially the fine forms, some of which settle as solid as concrete, but remain porous. These need to be laid on a base.
Hardwood posts or cypress pine are great posts.
And yes, concrete looks cold. The minimalist, cold look won’t last. People look at the finished product and instantly want to ‘soften’ it. Fads never last.
Alison