Landscaping trends are constantly evolving, as we contend with changes in climate, and innovate new and better means of dealing with the challenges of shaping a landscape to our tastes. One technique that has gained popularity in recent decades is permeable versions of traditional surface materials such as concrete and asphalt. While this may not sound particularly exciting, this can have a huge host of benefits (and, yes, a few drawbacks as well).
Pervious concrete, sometimes called permeable concrete or porous concrete, has been in use since the 1800s, but until the 1970s it was nothing more than a cost-cutting measure: its porosity naturally means that it requires less material than traditional, solid concrete. Only in the last fifty years have we discovered the many useful attributes of building with permeable materials.
Regular concrete is made by mixing aggregates (variously-sized particulate materials such as sand or gravel) with cement and water to bind the aggregates together. To make pervious concrete, you simply refrain from using fine aggregates. Where the minuscule bits of sand and crushed rock would fit into the structure of regular concrete, you are left with negative space. When prepared correctly, these voids form a network of interconnected tunnels that allows liquid to pass directly through, as they would through a sieve. As with regular concrete, however, it’s not as easy as it sounds: factors like temperature and fine-tuned ratios of the aforementioned ingredients can have outsized effects on the durability of the final product.
Arguably the biggest upside of building concrete flatwork out of permeable materials is the environmental impact. Pervious concrete allows water to drain directly through it, reducing runoff from paved areas. This means less flooding and erosion, and it greatly obviates the need for things like stormwater retention ponds and high-capacity storm sewers. Additionally, this direct drainage greatly increases the recharge of local groundwater, a precious resource in many places. Pervious concrete can even prevent a great deal of pollution from entering the groundwater reserves, both by reducing the amount of road dust and other harmful particulates picked up by the water during runoff, and by actively filtering the water as it drains. The local flora will also benefit from the significantly increased airflow and water flow through the pavement to the root systems.
In other areas, there exists a mixed bag of pros and cons. Pervious concrete is generally more expensive than its nonporous counterpart, although this gap is shrinking gradually as pervious building materials become more mainstream. In many cases, however, it could end up paying for itself, as it might save you having to deal with expensive property damage from flooding and erosion, and (depending on the specifics of the construction project) it may alleviate the need for more complex and expensive auxiliary drainage systems.
Finally, cold climates present a challenge to those looking to pave with permeable materials. Due to the negative space within the structure, pervious concrete will always be less durable than standard concrete, which is why it is not used in load-bearing projects like highway overpasses and bridges. This also means that pervious concrete is prone to breakage in situations where water freezes before it has had time to drain out of the concrete, making standard concrete a much more viable option in some climates. On the other hand, while standard concrete may not break in such situations, it will instead develop a layer of ice on top, presenting a hazard to pedestrians which is not a risk with permeable concrete.
Not all of these attributes will factor into your choice to use permeable or standard concrete in the construction of your perfect backyard landscape. Your situation, vision, and priorities are unique to you, and it’s important to take into consideration things like climate, soil and bedrock composition, incline, vegetation, and many more, before committing one way or the other. Our visionary landscape experts are here to guide you through every pro, con, and what-if, so that you can be confident in this decision, and all of your landscaping decisions. Book a consultation today, and take the next step toward the property of your dreams.
