Leon Krier – Transect T4 – american towns
The 30-minute slide lecture presents a formidable challenge: Can we boil down a message as complex and multi-facetted as ‘good’ urbanism into a small set of manageable principles? Probably not, but that’s no reason to stop trying.
Main and 3rd Avenue
Five Principles for Mount Pleasant Urbanism
- Neighbourhood footprint
- Built Form
- Street Space
- Social functioning
- GHG-Zero Transportation
Five principles in urbanism can deliver walkable neighbourhoods and livable streets to our longstanding, most venerable neighbourhoods. We can obtain these results in the places we call home by restructuring them as a series of quartiers centered on the place of original settlement; building the urban paradigm with human-scale buildout; delivering social housing in sufficient numbers to meet demand; rebuilding arterials to support social functioning; and removing car trips from the street.
1. The footprint of urban neighbourhoods
The district is the cellular unit of the quartier. In turn, the quartier is the cellular unit of the neighbourhood, and the neighbourhood is the cellular unit of the city. We build great cities one ‘good’ neighbourhood at a time, and we build good neighbourhoods one ‘good’ quatier and district at a time. The word ‘good’ is used in quotations to remind us that the performance of cities, neighbourhoods, quartiers and districts can be expressed in concrete and verifiable terms. In other words, urbanism is a normative science, and urban planning practice consists of the prescriptive application of its tenets.
Urban districts should present continuity of character and diversity of built form. The pattern of districts can be shaped to support social functioning by placing build out within easy walking distance of local destinations and transit (see 5 below).
In memorable historic neighbourhoods we find:
- The heart is near the place of original settlement.
- A Civic Space occupies the heart.
- Neighbourhoods are composed of clusters of quartiers centred on the heart.
- Quartiers are shaped by districts focused on local places or destinations.
- There is a park or square within a 5-minute walk of every home.
In Mount Pleasant—the most significant of Vancouver’s first neighbourhoods developing outside the downtown—additional opportunities present:
- Add a transit stop in each quartier or pedestrian shed.
- Plan incremental build out and transit implementation together to repair urban fabric and achieve revitalization in the arterials.
- Calculate buildout density for each quartier, then tabulate the total supported density for Mount Peasant as a whole.
West side of Main Street between 8th and 7th Avenues (1922)
2. Built Form
Memorable historic places achieve urbanism with human-scale product. Human-scale product in Vancouver—expressed as Floor Space Ratios (FSR: total building area divided by lot area)—yields the following densities:
- 2.0 FSR outright;
- 2.5 FSR on sites providing social housing; and
- 3.0 FSR when the additional space is located below grade.
Human-scale buildout on single family lots fronting arterials can achieve urban densities combining perimeter block massing and continuity of the streetwall. Continuity of the streetwall adds definition to the public realm; while perimeter block massing achieves separation between units in the block middle.
3. Street Space
Human-scale streets result from setting the height of the streetwall in proportion to the width of the fronting right-of-way. The proportion of streetwall height to width of fronting right of way is the street aspect ratio (SAR). The SAR determines the separation between fronting units; retains views of the sky; and achieves solar penetration to the ground plane year-round.
- In northern cities SAR is calculated to maximize solar penetration year-round.
- In Vancouver an SAR of 1 : 3 (17°) allows year-round solar penetration to the sidewalk.
- SAR applies to ALL fronting rights-of-way including the fronting street, flanking street and lane side.
- Rear gardens & courtyard spaces help achieve 1 : 3 SAR lane side.
- The building mass is set below the extended line describing the Street Aspect Ratio.
4. Social Functioning
The manner in which buildings front public rights of way can support social functioning and enhance the sense of place.
- Building lots give back the first 10-feet of property to widen the public ROW;
- 22-foot sidewalks support outdoor uses & cafés;
- Residential front doors and front door yards open on the street;
- Pedestrian oriented street lights enhance the sense of safety at night;
- Street tree planting at close centres can adjust the sense of place in the street.
5. GHG-Zero Transportation
Transportation and neighbourhood planning should be integrated.
- A transit stop is within easy walking distance of all units.
- The old streetcar network is rebuilt as a GHG-szero electrified network of trolleys and trams.
The 5 Principles have been tested against proposed new development in Mount Pleasant today. The results are consistent and suggest that the Mount Pleasant principles should apply to all redevelopment in Vancouver neighbourhoods outside the downtown core in order to safe guard values of community and values of place.