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Prefurbia, Part II: Nonlinear Organic Approach to Design

by Rick Harrison, Rick Harrison Site Design Studio

The top image shows a "brow" built in an Omaha housing tract to stretch the setback line to gain density, but it fills almost the entire area with paving. If we keep the setback line as is and eliminate the brow paving (bottom photo), the area takes on an entirely different appearance. "Coving" relies on a different foundation, stretching the setback line and reducing street length. The home fronts now face a more organic "park-like" area that forms a "cove" along the street.
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In part one on the methods of Prefurbia (LASN Sept. issue) we demonstrated the concept of designing the main pedestrian trails first, then the street pattern. We touched on the concept of flow and traffic diffusers and in general using fluid design instead of linear thinking.

Part II concentrates on expanding upon this nonlinear organic approach to design, which should be a natural for landscape architects to embrace.

To further explain "coving," we look at two site plans, the before plan (above), and the after plan of Placitas de La Paz in Coachella, Calif. The before plan is a half-mile long and has a one-side fronted street along each side. Essentially a half-mile of street not being used (at $300 a linear foot, that almost $800,000)! The after plan has 18 percent less linear feet of street. Also note the walks that cut through blocks for pedestrian connectivity.

The shortest distance between any two points is a straight line, right? It is natural to think that a linear tight grid pattern would be more efficient than the free-form and willy-nilly patterns of streets stereo-typical of the suburbs. You will soon find out what appears obvious is not necessarily so!

Prefurbia began as an evolution of a singular design called coving. Coving was a new design technique in land planning that:

  • Created an independent relationship between the shape formed by the homes along the front setback and the shape of the street.
  • Promised economic and environmental advantage to the developer and municipality.
  • Had the ability to increase density and space if the municipality would allow density increases.

Coving is simply a geometric pattern. If done correctly it can have tremendous advantages over conventional geometry. Because coving is more art than science it is difficult for linear thinkers (surveyors and engineers) to master. Coving takes somewhat of a vision, making it an ideal foundation to advance landscape architectural design.

Entering the Placitas de La Paz neighborhood in Coachella, Calif., you are lead to a central circular park along streets that discourage speeding and maintain a constant rate of flow, reducing time and energy.

Prefurbia does not require coving, as Prefurbia is a collection of methods that balances livability, economics and environment. However, when coving is applied to a multitude of design situations it opens up opportunities.

Stretch the Setback Line and Reduce the Street Length
Before coving, density was a function of creating as much street frontage as possible. Home fronts that paralleled the street achieved density only by lengthening the street. Thus, the more street, the more lots. However, you have the most costs and environmental impacts with the smallest possible lot size. The top left image shows a massive amount of street built to form a "brow". The reason for this brow is to stretch the setback line to gain density, but it fills almost this entire area with paving, destroying the economics and environment. If we were to keep the setback line as is, and eliminate the paving, the area takes on an entirely different appearance.

The homes (okay, the garage doors) now overlook more of an organic "park-like" area that forms a "cove" along the street. We separated the rigid relationship that is commonplace between the setback line and the curb. No regulations were broken, nothing moved, the developer does not pay for the expense of the brow, and the city (Omaha) no longer pays for repaving and snow removal. The length of the walk along the brow is now smaller, it meanders making it more inviting, and driveways taper efficient.

Landscape architects can work their magic to make the below more attractive and literally have tens of thousands of extra dollars that would have gone towards extra paving now go into character building elements.
A "cove" is the meandering open space that forms along the streetscape when the homes are set precisely to form shapes that create interest and character.

With coving, the secret to gain density is to use as much street frontage as possible. Build less street, you have more land area to work with. You also incorporate walks that cut through blocks, providing pedestrian connectivity.

This image shows only the shapes created in the Performance Planning System that comprise the exact areas of manmade structures as well as the data structure of ownerships (lots, common areas, etc). All line work is deactivated. The meandering front yards (coving) are in dark green to emphasize the park-like setting of the streetscape. Common areas are in a lawn green color. The private rear yards that can become fenced or cluttered with stuff people collect over time is in lighter green.

Harnessing the Curves
It is possible to produce a coved plan using a straight street grid, and we have done those in urban redevelopment work where the grid street pattern could not change. The efficiency however, comes from harnessing the curves.

Again, without the ability to "flow" the street pattern, taught in Performance Planning System (PPS), a curved design could spell connectivity disaster! Entering the Placitas de La Paz neighborhood in Coachella, Calif. (photo at left), street design discourages speeding and maintains a constant rate of flow, reducing time and energy. Note how the built environment is almost exactly like the original proposed plan (p. 101 photo). This brings us to another point about coving. There is no room for a fudge factor. The plans must be precise at the sketch stage to assure a high level of street efficiency.

Almost all ordinances have two requirements: lot lines perpendicular or radial to the street, and most regulations require a tangent between curves. These regulations originated before automation, when every plan had to go through a manual "plat check," which would have been extremely difficult to accomplish if these two rules did not exist. Today these two regulations make about as much sense as requiring a hand crank to start a car. So, for the past 650 neighborhoods we have designed, we have ignored these two rules.

This drawing shows the initial setting of groups of homes and the lot lines that pass through or past the minimum "setback" lines. This form of design always assures that the home setting is given priority, not an afterthought somewhere long after the development is under construction, as is typical with subdivision platting.

Civil Engineers and Land Surveyors
Engineers and surveyors who designs as if CAD had only two commands, the line and the offset command, is likely to tell the developers behind closed doors they are making a serious mistake going this more organic route, which will put a burden on them to design and stakeout outside the box. You need to determine this right away - before you even think about taking on a coved design. If you fear the engineers and surveyors will not be an asset, you must bring this up to the developer who can find consultants that do embrace this new era of design.

Once you embark on coving you are likely to find that all others will embrace the design. You might think the plat would be very different, from a conventional one. Street right-of-way, side and rear lot lines remain the same as well as lot ownership and responsibility. The meandering walks are typically set in public access easements (not indicated here). The setback line is typically represented with dimensions to the setback line along the lot sides.

The homes must be built so that the home front matches the recorded setback for the effect of coving and the advantages to work properly. This requires engineering and surveying to be on board at the beginning and through completion. When we teach coving, we recommend placing the homes first with phantom (temporary) lines representing front, side and rear setback minimums.

The Home Setting is the Priority
While PPS does not specifically teach how to cove, it recommends this form of planning for all residential design. This form of design always assures that the home setting is given priority, not an afterthought somewhere long after the development is under construction, which is typical with subdivision platting.

Unlike Smart growth, New Urbanism, TND, etc., planning which dictates a long list of strict set of rules to follow, coving has only one rule that is critical. That rule is there are no rules. Let your imagination and artistry soar. What we have is recommendations from almost two decades of experience that can be downloaded at

High-Level Organic Design
PPS was specifically developed for high-level organic design, so we concurrently developed methods, technology and education to help those that want to take on coving and master it.

Coving requires a lot of practice to maintain density, while reducing a significant amount of infrastructure without allowing the curved design to be dysfunctional.

Now throw in the design advantages of Prefurbia on top of coving and you have the equivalent of the kind of experience an instrument rated pilot has. It's not easy, but worth the effort.

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August 24, 2019, 5:39 am PDT

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