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Prefurbia

by Rick Harrison, Rick Harrison Site Design Studio




We begin by designing the main pedestrian area. The yellow lines indicate the main eight ft. wide walk connecting pedestrians to commercial uses to the north, the multi-family to the west and single family to the east.
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Prefurbia is a collection of new methods to design sustainable neighborhoods. You have probably heard that term before, but these articles will prove the economic, environmental and social benefits of Prefurbia.

Moving planning beyond simple geometry is all about knowledge. It’s not about technology, but many of the new methods are made practical to implement because of technological advancements. Landscape architects can now create “plat” accurate plans that are more fluid in design, embracing natural systems.

 




Now we set the street geometry. The prior plan used the “offset” command in CAD to create rigid patterns. The meandering Prefurbia “Main Street” incorporates a series of island traffic diffusers to maintain flow and provide one-way lanes for pedestrians to cross, increasing safety.


This article showcases some design advantages Prefurbia offers.

In this first example, we have a before plan used to benchmark advantages. Performance Planning System (PPS), a blend of software technology and education, was specifically developed to handle the demands of advanced planning and analysis and is the platform used in this series. PPS combines the accuracy of a land surveying, the spatial power of GIS, a graphic editing presentation and the simplicity modeled after PowerPoint.

The Before Plan

  • High-density apartments along the north.
  • 76 town homes to the west.
  • 52 single family lots to the east.
  • Commercial uses buried in the center of the site.

There are 7.7 acres in the southwest section of the site that are not part of this design. The site slopes down gently from east to west.

The plan is geometric, something easy to create in any CAD system. There are many repetitive patterns, which in CAD could be designed with a few keystrokes. There are also many problems with the design from a regulatory perspective. The single-family street is 24-ft. wide (the city minimum is 34 ft.) and there was no right-of-way, which would have zero chance of approval. The main street lanes are 8 ft. narrower than minimums.

After importing the original plan into PPS, we create shapes on all of the improvements. Pointing into a closed area, PPS compiles the boundary with a “shape name” you determine. To compile walk geometry, name those shapes “walk.” Each name is on a list and assigned a color, texture, or crosshatch pattern and also flagged as being impervious, pervious, or ignored for determining environmental density (E.D.).

 




Light grey = fronted public streets. Red = public streets built without useable frontage. Darker grey= private drives. Light blue = drives not used for parking. Darker blue = half-wasted drives. White = five ft. wide walkways. Twenty-six percent of the paved areas were “wasted” space.


After creating shapes, a clear picture of the before plan efficiency emerges.

  • Light grey represents public streets that are fronted (being utilized). —Red areas are public streets built without useable frontage (we counted commercial exposure as useable frontage).
  • Darker grey areas are private drives.
  • Light blue areas represent drives not used for parking (creating waste).
  • Darker blue represents areas of half wasted drives.
  • White areas are five ft. wide walkways.

Of the 6.95 acres of private paved surfaces serving multi-family and commercial uses, we identified 26 percent wasted space. Of the 4.19 acres of public street surface area, 55 percent is waste! To conform to regulations the public streets, the actual paved surface area would consume six acres!

P.O.D. (Pedestrian-Oriented Design)

We begin by designing the main pedestrian system.

The yellow lines indicate the main eight ft. wide walk connecting pedestrians to commercial uses to the north, the multi-family to the west and single family to the east. Because this site is flat we will use straight walks that can be tree-lined. Every site is different, but in general our style is to use straight paths if possible.

Prefurbia neighborhoods encourage residents to take a stroll.

Next we set the street geometry. The prior plan used the “offset” command in CAD to create rigid patterns. The meandering “Main Street” incorporates a series of island traffic diffusers—each with their unique identity to maintain flow (reducing time and energy), and provide one-way lanes for pedestrians to cross, increasing safety. The easterly street meanders to calm traffic through the single-family area and provide a foundation for “coved” geometry. We saved the trees.

 




Emulating natural systems, we throw out the tee-square and triangle, and concentrate instead on fluid shapes.


Emulating natural systems, we throw out the tee-square and triangle, and concentrate instead on fluid shapes.

  • Setting homes so each structure forms a meandering shape eliminating monotony while increasing efficiency.
  • Varying space along the streetscape provides a low-density feel while creating a foundation for landscape architects to create some wonderful effects.
  • Gently winding the secondary walkways.

We typically place the main trail as eight ft. wide and the secondary walks at a useable six ft. width. Every home on the development has a walk convenient to their front porch.

Prefurbia design theory hides unsightly rear yards when driving or strolling along the streetscapes. The homes are shaped to fit the lots.

The goal in the conversion from a plan that did not conform to existing regulations (unapprovable) to Prefurbia was to create a better neighborhood, conforming to existing minimums, with the same density and commercial lease area by converted the apartment area to commercial uses on the after plan.

 




Varying space along the streetscape provides a low-density. We typically place the main trail as eight ft. wide and the secondary walks at a useable six ft. width. Every home on the development has a walk convenient to their front porch.

 

Enviromental Density

The main pedestrian trail interlinks the neighborhood and creates shops as a destination (neighborhood marketplace) within the open space.

The environmental density (ED) is a new term in planning made possible by the automation in PPS to measure the impervious surface area (manmade structures). This has two important impacts: one environmental, one financial.

ED is a way to measure efficiency of the neighborhood design.

The conventional plan ED from the original CAD is 0.457910, or 45.8 percent of an acre is manmade surface.

The plan delivers an ED of 0.402606, or 40.2 percent of an acre is manmade.

To comply to regulations, the original plan’s ED would be approx. 46.1 percent.

A reduction of 5.9 percent might not sound significant, but that represents a reduction of 2,570 sq. ft. for each acre or 3.1 acres less “manmade stuff” on the 52-acre site. The plan has 60 more parking spaces and the residential units are about 10 percent larger. There are 64 single-family homes and 64 town homes (50 percent each), as opposed to the original plan where 68 percent of the units were lower income attached.

The organic nature of Prefurbia conforms to odd-shaped sites and difficult topography. The time and energy to traverse through the neighborhood by foot or by car is far less, and the environmental impacts plummet. Prefurbia does not meet the minimums demanded by the cities ordinances—it exceeds all minimums, thus is easily approvable!

The foundational theory of Prefurbia can be found in the book by the same name, and PPS provides both the teachings and technology to make this form of organic design practical.


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August 24, 2019, 10:47 pm PDT

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