Hardscape (the man-made features used in landscape architecture, e.g. paths or walls, as contrasted with vegetation) serves as the structure and framework for your home garden. This makes it an essential item to address in a design or redesign, especially if you want to create a sustainable garden. Being informed about different material choices will help you make the right decisions to reduce your environmental impact when building or shopping for your dream garden. In this blog post, we will take a high-level look at the topic but know that just like most things, one could dive much deeper into the subject.
Not all materials are created the same! There are many things to consider when it comes to evaluating a physical building material’s environmental friendliness. Anything from the carbon intensity needed to manufacture it, to sustainable practices when it comes to harvesting (if it's a natural material like stone, wood, or aggregates). Other things to take into consideration are how far your material is traveling to get to your doorstep or material yard (think carbon footprint here: local/regional is usually better), material or production certifications, the material life-cycle (Cradle to Cradle) and durability, as well as its potential to be re-used or recycled. As mentioned, we won't be taking a deep dive into each of these sections, but rather list a few hardscape materials we see as environmentally friendly and why. Using a similar lens, with the above specifications, will give you the toolkit to evaluate if materials will check the boxes you want them to or not. Searching for green building solutions for the outdoor landscape is not all that dissimilar to shopping for indoor green building solutions.
It should also be noted that hardscape materials that already exist in the garden, and if they are in good condition, will not only be the most budget-friendly to keep but also have the least environmental impact. That’s because they are already in place and getting rid of them has environmental implications from waste refusal to recycling and the carbon footprint of transport. Sure, your existing old concrete pathway would be better or more attractive as permeable paving or gravel to percolate water into the soil, but using that budget to perhaps plant more native pollinator plants around the garden would be money better spent.
Although typically one of the more expensive material choices for outdoor paving, it can be one of the most aesthetically pleasing, durable, and effective hardscape materials. However, there are a few criteria that should be met. Primarily, the stone should come from a certified source or quarry. The criteria for this are a bit convoluted, but luckily the ANSI/NSC 373-Certifications seals of approval make these easy to identify. Sadly a good amount of beautiful stone you will find at stone yards or materials places have traveled many, many miles, and often from abroad like China, countries in Europe or elsewhere, where material is cheap, and is sometimes harvested unethically. Secondly and ideally, the stone should come from local or regional sources to be considered more sustainable, as there are transportation costs associated with its environmental footprint. However, this, unfortunately, is not always possible, depending on where you live.
Permeable stone paving is arguably one of the best forms of hardscape because it allows water to percolate through the joints back into the water table and surrounding landscape. This is a form of low-impact development, which reduces runoff and pollution in the surrounding urban and suburban context. Please note that permeable paving needs to be set up properly to function well, with adequate subgrade aggregates, setting beds, edging, compaction rates, and so forth. It’s best to consult a professional on this piece, but a seasoned DIYer could certainly take this on after doing some research!
Wood is another excellent environmentally friendly landscape material that can be used for all sorts of purposes like screening, siding, furniture, paving (decking & boardwalks), structures, and many more. The incredible benefit of wood is that it is renewable and can be regenerated. However, like stone, wood comes with a huge caveat, which is that it needs to be grown and harvested sustainably and ethically. The main seal of approval to look for here is FSC certification. Sourcing domestically grown wood would be the most sustainable. However, you will be limited in the types of wood you can buy (tropical hardwoods like IPE, for example, will always have to be imported).
Luckily, wood comes in many types and production methods as well. Many folks like to use natural woods, which can be sealed and protected to last longer (we won't get into the weeds on sustainable sealants here, but generally, I would always recommend natural oils vs. petroleum-based sealants and lacquers). Many woods have natural elements that make them durable and pest-resistant, like their composition, oils, and other characteristics. However, other new technologies are coming out each year that showcase different wood preservation techniques that make softwoods more durable and sustainable, too, like Thermally modified ash or even pickled pine, just to name a couple. Last but not least, there is always the option to use fake or composite wood. The company Trex might come to mind. While they typically are plastic (which is a petroleum-based product), they tend to use high amounts of recycled material, which helps offset its negative carbon footprint. There are many brands to sift through when it comes to composite decking, and each uses their own technologies, base ingredients, processes, and pricing, so we would invite you to browse a couple to your liking if composite is the way you want to go.
Small aggregates like gravel or decomposed granite can be really great garden materials for your pathways, patios, and driveways. You may be starting to sense a theme here, that just like with wood and stone, the material is really only as environmentally sensible as its harvesting, production, and transportation methods.
It should be noted that the benefits of decomposed granite are more enhanced if the material is ‘stabilized’ (meaning it gets sealed and hardened to hold together better). This makes DG last longer, have less runoff, and permeate moisture better. Unfortunately, many of these binders on the market today have toxic elements in them. Luckily, there are brands coming about that are using plant-based polymers and non-toxic binders, so we would strongly urge you to use those.
Gravel is a bit more straightforward as it sits over a compacted aggregate base, and is simply laid down without a binder. So, the main way to ensure it is considered more ‘sustainable’ is to use local materials. This will also ensure that your garden pathways feel ‘of the place’, as the textures, colors, and finish will all look and feel more local.
Concrete is the most popular building material in the world, with about 70% of us living in some type of concrete-supported structure. Unfortunately, it also accounts for a huge amount of pollution and negative environmental impacts, mainly due to its energy-intensive production methods. However, it is tough to beat its cost-effectiveness, variability, durability, and other factors, which is why so many folks still use it today. It has many applications in the landscape from pathways, to pavers, walls, and structure foundations.
Fortunately, there are companies out there who are disrupting the concrete industry, and there are a variety of more ‘green alternatives’ coming about. For example, using reclaimed fly ash, waste slag or other industrial manufacturing byproducts instead of Portland cement, using different more sustainably sourced aggregates, and partially recycled material. Others are actually injecting carbon back into concrete during the production process to lessen its negative effects, creating pavers that actually absorb carbon, or crafting machinery that can capture the negative byproducts from the concrete production process to be then re-used elsewhere in the cycle.
Unfortunately, many of these ideas aren't at full scale availability to the average consumer, so we would still advise using minimal amounts of concrete whenever possible, and use sustainable practices that are available when possible, such as more porous approaches to hardscape.
We have gone over a few materials and what makes them more sustainable. Generally speaking, we are looking for local and regional materials whenever possible. Closer to home means less transport emissions. Then, we want to make sure they are ethically sourced through the various rating systems depending on what material we are looking for. Lastly, we want to make sure the material is appropriate for the site, fits the budget, is durable and/or recyclable, and, of course, functions well for what you need. We like low-impact yet durable materials that allow nature to do its thing and allow us to have a symbiotic relationship with the land.
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