Tuesday, March 5, 2013

Urbanite the stuff of...oh nevermind!

Welcome back to another episode of lost in the farmer’s market! As you can see we are getting closer to the wonders of spring and the delightful harvests of summer. Outside the birds are back as scores of sparrows, catbirds, cardinals, thrashers and, robins are out singing their little heads off. As for you the gardener you have heard me talk about seed catalogs and planning and well I think I sort of beat those topics to death.  Today’s topic is a wild card that came up while out on a work site this week.

Today’s topic is “Urbanite” and no, this is not a country term for a city dweller. Urbanite is a residual byproduct of urban development and is commonly available for free where ever construction is going on. In short the material called Urbanite is really scrap cement from sidewalks and foundations, its cheap durable and no harder to use then field stone. I admittedly have no idea who first came up with the term “urbanite” but I do know that it is a catchy term that sounds much better then ‘scrap cement’. Plus I can imagine if one were driving about town in a pickup truck looking for areas to “quarry” urbanite it probably would not be that hard to find. New construction or refurbishments of buildings or even the replacement of a sidewalk can provide a lot of urbanite. I have to state that of course as with any salvage item you should ask permission before hauling anything off.

I realize that some of you out there may be thinking we’ve gone bonkers at LITFM with the urbanite suggestion. Others might be flat out thinking something like the following.

“Eww its busted cement why would I use that?!”

The obvious answer is the cost of stone and brick. For note a ton of ‘black forest’ field stone costs between $150 and $200. A single band of Pinehurst type bricks at retail level will easily run you a little below or above a hundred dollars. When I say castle block typically used to make retaining walls isn’t cheap, I mean it. Honestly shelling out two to three dollars per 22 pound castle block and knowing you will need at least three concourses means you will be digging deep in your pockets.

 I might add I am no fan of impermeable surfaces such as pavement but since concrete is generally a mix of sand, gravel, lime and a major sticking agent it is actually semi-permeable.  Since Urbanite is semi-permeable, this means it can aid in moisture retention, and since it’s essentially artificial sand stone it could aid in keeping the soil warm. There is also the chance that if the urbanite you use was made with lime as it weathers it may help in countering acidic soil Ph.

This is the naturally occurring form of urbanite.

That aside I won’t sit up here and say that urbanite is the wonder material of tomorrow as it has its difficulties. As you can see in the above picture, the urbanite pieces are quite variable in size and shape. The below picture depicts a retaining wall-raised garden bed combination is made of irregular pieces of urbanite some of which are four to six inches thick. This leads to a clear observation of the first and second natures of urbanite, the pieces are often irregularly shaped, and may be rather heavy. Even so, the above urbanite was used to make the below retaining wall. Now that’s not bad,  we have a curved retaining wall that is relatively pet-proof due to height and can be cultivated to add to existing garden space.

Stacked Urbanite can make for interesting raised beds.


A major use of Urbanite can be found at the link above. That link goes to the web log of the Suburban Hermit of Fayetteville.  Look closely at the walls used to make his terraces, that’s finely lain urbanite but you wouldn’t be able to tell if you didn’t see it in person. It looks comparable to the finest dry laid field stone walls. Quite literally that is the best case scenario, think of how much urbanite is not in a dump somewhere because he turned a waste byproduct into a functional material.  I might add that you too could do this; it would only take some initiative and a source of urbanite.

Now I have to make some observations about the two demonstrated uses of urbanite. In the first example the retaining wall has visible amounts of tumblehome; as the bottom is visibly wider then the top. This design aspect is common in load-bearing walls because it spreads out the weight of the earth behind the wall and any water weight across a greater surface area.  Additionally the slope, height and curvature serves both to stop soil erosion, create a micro-climate and it happens to be pet proofed.

In the case of the Hermit’s work, his contoured urbanite walls are part of a cleverly designed and complex integrated terracing system. The core of what he did is to negate a bare slope with little in the way making this potential terraced backyard garden utopia. If you looked at his blog photos you can see he crew all kinds of cool stuff very successfully. This means that both his terracing is wildly successful but also his accompanying plant selections approved of his design and rewarded his efforts with serious productivity.

In short we are both combating erosion with the same material. Our style of construction and the reasons for why we built what we built are as different as the environments we built them in. In the end the Urbanite walls are unique, functional and work in different environments, and only you can determine which approach is best for you.  This brings us to the end of today’s episode and I might note that you can always contact myself via this blog, the Suburban Hermit of Fayetteville through his blog  or the meetup.org group Sustainable Neighbors on their meetup page about anything pertaining to urbanite.

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