I don’t usually get all gushy about cement. As a self-professed “softscaper” and plant lover I don’t have much use for the stuff. I opt for plantscapes and permeable surfaces over concrete. Then urbanite comes along and I’m just about ready to write a love sonnet.
“Urbanite” is the affectionate name for re-purposed concrete pieces. It’s a funny made-up-name for a common solution to a waste problem. I would even argue that the concept of urbanite could be raised to the level of metaphor because of its transformative role in restoring impervious, compacted, lifeless areas. This common resource is surprisingly available and is often used by creative landscape designers who seek building materials sourced from the urban waste stream. In ecological landscaping, urbanite is a material of choice and it has been a darling of the Permaculture movement for good reason.
Urbanite is easy to like for these reasons:
- It is a free material. However, it does take time to locate, and labor to load and transport.
- It is upcycled, which is the process of converting waste materials or useless products into materials or products with new value.
- There is no mining involved, unlike much of the raw material found in landscape supply yards which are mined in quarries. Flagstone and mossy field stone, for example. Yup, there’s a hole where that bolder once was.
- It is versatile. It can be used for a variety of hardscape purposes like patios, walkways, stairs, retaining walls, raised garden beds – and even herb spirals.
- It lasts. Isn’t that the definition of concrete?
The term “Cradle to Cradle” applies nicely to urbanite because it has been repurposed and can be repurposed ad infinitum. The upside of upcycling urbanite is that the embodied energy of the original concrete is captured. Embodied energy is a term to describe all of the energy that goes into the production of a product. It includes the manufacture, acquisition of natural resources, mining, transport, office administration and all other aspects of producing a product. Reuse of building materials commonly saves about 95% of the embodied energy that would otherwise be wasted.
Its usability is urbanites primary benefit because the manufacturing process of concrete has one of the heaviest carbon footprints of all building materials. The high temperature needed for cement manufacturing makes it an energy-intensive process. The average energy input required to make one ton of cement is 4.7 million BTUs—the equivalent of burning about 418 pounds of coal. For ready-mix cement it takes from 1,075 to 4,085 BTUs per pound. A BTU, short for British Thermal Unit, is a basic measure of thermal (heat) energy and is one way to measure embodied energy. Comparatively, it takes 123 BTUs per pound to produce adobe brick.
One of the tasks of ecological landscaping is to reduce overall inputs by sourcing materials with low BTUs per pound or by finding ways to capture embodied energy by upcycling, enter urbanite. Often in the process of redesigning a landscape existing concrete walkways and patios can be carefully deconstructed and turned into urbanite for the regenerated landscape. A brilliant way of capturing embodied energy right on site.
While the “embodied energy” assessment is an important piece in knowing the environmental impact of a product like cement, true full impact accounting takes it a step further by assessing all impacts on people and planet. In business this is referred to as “triple bottom line” accounting which includes “profit and loss” analysis in all the three realms of economy, ecology and equity. This includes considering the impacts of things like: Strip Mining, Clear Cutting, CO2 Production, Air Pollution, Fossil Fuel Use, Energy Consumption, Resource Depletion, Polluted Runoff, Disposal Problems, Worker Health Problems, Support of Irresponsible Companies, Damage to Cultures and the Effect on Communities. This is a stunning list of impacts that to a surprising degree come with the production of cement, the “feedstock” of urbanite. While each of these impacts can be debated, what is clear is that urbanite is a creative way to turn a nasty problem into an elegant solution.
The installation of urbanite takes some forethought. Like with other hardscape materials (such as flagstone), it is important to give urbanite a sturdy foundation. For instance, in preparation for installing walkways, patios or retaining walls, it is best to excavate 5 or 6 inches below grade and then install drainage rock and tamp well. The result is both good drainage and a solid foundation. This is important for liability reasons and because there are few things as disconcerting as a shaky retaining wall or shifting stepping stones.
Because concrete pieces are often chunky careful stacking is best done using guidelines from the mason trade. Dry-stacking, which means the process of laying pieces together without mortar keeps the material expense low. For a safe, tight result stack level using a hammer and chisel to correct uneven surfaces as you go always using protective eye wear. Because urbanite is heavy stuff get plenty of help when lifting and use your knees! Finally, a new stain is a good finishing touch. This can be achieved using non-toxic stains like iron sulphate (which is also is a fertilizer) or a product called SoyCrete for that new finished look. With all these environmentally and socially friendly reasons, when it is designed well and installed correctly we are very happy to give it the affectionate moniker of “urbanite”. – Ken Foster