The great density debate

by Sue James, Lovejoy

Seminar held on 28th February 2007 at the Innovations for the Built Environment Event


Bywater court, Leeds (courtesy, PRP)

A seemingly simple subject demonstrated its complexity by stimulating a well attended all day debate chaired by Dr Patrick Clarke of Llewelyn Davies Yeang with presentations on specific aspects by experts in their field. The day fitted into two parts with the morning spent exploring density themes and issues and the afternoon considering them in terms of case studies and delivery with a final summary and assessment by Professor Drew Stevenson, the Mayor of London’s Policy Adviser.

‘Density’ was explored through the housing density debate, but, as successful housing requires an integrated infrastructure (whether new or existing), it was clear that the discussion related to the urban realm as a whole. The difficulties of measuring density were discussed and it was agreed that, although ‘dwellings per hectare’ is a common measurement, people per hectare (pph) was a more useful way of measuring the actual density of an area in terms of numbers of users and therefore both capacity and intensity of use.

Dr Patrick Clarke set the scene by reviewing the situation after ten years of high density urban policy. Having described the need to establish virtuous circles for successful development he then demolished some “density myths”, for example, the notion that high density means high rise, since low rise can often actually provide a higher density proving that high density does not necessarily mean less living space in or around the dwelling. Density itself is a poor predictor of built form which is often circumscribed by other planning standards and a substantial array of design guidance documents.

What is more relevant is the link between density and land economy as the biggest land saving is achieved at densities of 30 dph and gains then start to fall. Another key measurement was the link between density and critical mass as a critical mass of people is clearly required to support adequate community and neighbourhood infrastructure services and facilities.

Urban land is being wasted

Recently much of the density debate has focused on areas of the Thames Gateway which offers a relatively clean sheet for developing ‘sustainable communities’. But research just published by Llewelyn Davies Yeang for the Campaign for the Protection of Rural England (CPRE) shows the very significant land bank of development opportunities within existing urban areas where, to a large extent, adequate infrastructure, services and amenities already exist and would, in many cases, be revitalised and improved if these developments took place.

Many potential sites are already within the “ped-shed” area i.e. close to existing urban centres. Dr Clarke concluded that there are lessons to learn from Europe because many European cities have continuously built on their urban traditions by honing and refining them over time. This is a very different approach to that taken in the UK since World War II where we seem to need to take major changes in approach to urban development, which are then reviewed and changed at regular intervals.

Urban vision: Suburbia or Eurotown or somewhere in between?

Professor Robert Bruegmann addressed the question of Urban vision: Suburbia or Eurotown or somewhere in between? How does high density urban development relate to the UK’s urban heritage and culture? Robert Bruegmann is Professor of Architecture, Art History and Urban Planning at the University of Illinois in Chicago and has been studying the issues of decentralisation and urban sprawl for the last fifteen or so years. (Sprawl: A compact history. University of Chicago press 2005).

Book cover of Bruegmann's book:Sprawl  
Density gradient

His contention is that there is nothing new about “sprawl” but it is an historical and intrinsic aspect of urban development – most people throughout history have moved out of cities as soon as they could afford to do so. He challenged many of the arguments of the “anti-sprawl” lobby. For example, Los Angeles, far from being an example of low density urban sprawl, covers a large area but since 1950 has been establishing itself as one of the densest urban areas in North America in terms of people per hectare. Most people, anywhere in the world, ask for detached houses on their own land.

This requires suburban development or “sprawl” usually encouraging greater use of private cars which creates more pollution. Is this true? In Kansas, a low density city, the journey time to work is 20 minutes while in Tokyo, a high density compact city, the journey time to work is 46 minutes. In Paris a commute by car of 26 minutes can take 57 minutes by public transport.

Does low density development necessarily present the adverse environmental conditions that the detractors of “sprawl” claim? In New South Wales in 2005 it was found that single family houses used less energy per capita than apartments and at low densities of 1 or 2 dwellings per hectare, each dwelling could generate all its energy on site. Equally, it is also the case that, provided people have enough money to live in dense city centres, there are those who respond to the social and cultural stimulation of central city living. People often make different choices for different reasons at different times in their lives.

When considering aesthetic issues, Professor Bruegmann, explained that, while central London slum dwellers were grateful to move to the newly built 19th century suburban terrace houses, intellectuals and architects of the day saw the concept as a nightmare of sprawl encouraged by greedy developers. These are the very terraces that today are claimed as part of London’s urban heritage, which demonstrates how dramatically we are able to change our minds.

The great British anti-sprawl campaign began with the Abercrombie London Plan in 1944 which established a Green Belt around London and ultimately encouraged the development of garden cities and new towns to accommodate the excess urban population. One effect of this policy, Professor Bruegmann contended, is that restrictions created by the Green Belt and greenfield policies have restricted the supply of land and pushed up house prices to levels compared to income that have never been seen before.

This has created a backlash to anti-sprawl and high density campaigns led in the UK by groups such as Audacity who consider that 5 million houses are needed and to make them affordable relative to income they may need to be built on greenfield sites.

So, suburbia or Eurotown or somewhere in between? Professor Bruegmann said that he was an agnostic on the subject, but it is probably somewhere in between.

Happiness per hectare: is high density development delivering?

The second stage of the morning’s discussions considered the question of Happiness per hectare: is high density development delivering? The first of three speakers, Ben Page of Ipsos-Mori, speaking in a personal capacity, said that his research could find no correlation between density and happiness. What matters to most people are amenities, appearance, good public transport links, and quiet areas.

When considering what is important for quality of life, people identified low crime, activities for teenagers, decent roads and quiet streets with low levels of traffic and a well-cared for public realm. Is it just about being clean, safe and green? Certainly leafy places score highly but also good design and good maintenance – places that are cared for, with no sense of dereliction - are important for enhancing happiness. But what do people’s preferences in terms of housing choice mean for density?

Most people over 54 prefer bungalows; 16-54 year olds are comfortable with the concept of “Poundbury” type developments and, although 10% of young people expressed a preference for modern housing, most preferred the Poundbury model. No one canvassed wanted to live in tower blocks.

High quality design is essential

Andy von Bradsky from PRP Architects considered a customer driven approach. He suggested that housing designers could learn allot from the car industry with a focus on the needs of the user and continuous production development constantly responding to the customer. What people want mostly seem to be houses and gardens rather than flats; low rather than high densities; places to accommodate cars; suburbs rather than town centres and these aspirations are in conflict with the high density/brownfield approach.

Choices are influenced by location, schools, access to shops and services and perception of the quality of a place. If the Thames Gateway, for example, has no or limited infrastructure and poor design then it will not attract higher income owners. People perceive high density areas to suffer from higher levels of crime and anti-social behaviour. Higher density designs can create customer satisfaction if they get the mix right – integrated communities with a housing mix that includes family homes; early establishment of physical, social and cultural infrastructure and identifying sites which extend the edges of town locations or regenerate existing suburbs.

Above all, ensure high quality designs which also satisfy practical needs such as security, sound insulation between dwellings and privacy from overlooking with a well-designed and well-maintained and managed public realm and amenity spaces.

Paradise St, Oxford (courtesy PRP)

How much open space do we need?

Martin Kelly of Lovejoy London reminded us that there is no one size that fits all solution and successful schemes are a combination of character, location and context. As a landscape architect Martin focused on external spaces and the value attached to open space and key issues relating to creating a successful public realm such as intensity and type of use as well as maintenance and long term stewardship.

How much open space should be provided per person in housing developments? There are guidelines but no statutory requirements for this. In 1944 Patrick Abercrombie proposed about 16 square metres per person. Today, the Mayor of London has defined areas of deficiency as more than a one kilometre walk from accessible Metropolitan and Borough sites.

In terms of user satisfaction, research on Density by The LSE Cities team showed that satisfaction in higher density areas was increased if there was access to open green space of more than 10 hectares within a 10-15 minute walk from the home (800-1200 metres) and that smaller green spaces needed to be well-maintained and feel safe, but would be used for brief events such as lunch breaks rather than places to spend more extensive periods of time over holidays and week-ends.

What is now recognised is that outdoor spaces close to houses as well as pocket parks or larger open spaces are needed to provide satisfactory settings for daily life in the home environment and these can be provided in the form of private gardens, shared or community gardens, balconies or roof gardens. It seems that successful developments have a range of age groups in the resident mix but child densities should not exceed 25%. A recent CABE report on the views of residents on the design of new housing noted that people want to see the car “tamed” but not banned and many would sacrifice private open space for parking.

Martin Kelly also explained that it is important to recognise capacity and intensity of use as some areas are particularly vulnerable to over use – areas such as lawns, play areas and areas of biodiversity and natural landscape. It is important to understand the needs and aspirations of existing or anticipated users groups. At the same time public and private open spaces should have flexibility so that they can change as required over time. Maintenance and long term stewardship is another key component of successful developments. These should be designed in from the outset and long term maintenance programmes and funding should be considered at the development planning stage.

Case studies of high density schemes

Tom McCartney launched the afternoon debate by presenting his successfully delivered scheme for the Crown Street project in Glasgow (pictured above) and his recent work as CEO of Sunderland ARC. Tom’s view was that if you put density into context you will see that there is nothing new but the density discussion runs in cycles of preferences for higher and lower densities.

Crown Street is in the Gorbals in Glasgow. The Gorbals are close to Glasgow city centre and every type of improvement policy has been tried out there. In the early 20th century the Gorbals were canyons of 4 storey tenements with the highest densities outside Calcutta! The flats were very small and the residents response was to create an active street life. In the 1950s and 60s Basil Spence and Robert Matthew were the architects for the area’s redevelopment. These were urbane, educated architects with a vision of building a brighter future for Britain. The results proved to be a disaster and demolition took place in the 1970s.

The replacement scheme by Piers Gough of CZWG recreated the urban grid pattern and achieved relatively high densities of 3-4000 residents (110 dph) but these are low in comparison to the 120,000 crammed into the original tenements. The emphasis of the new scheme was on high quality design and good maintenance.

The same focus was used for the Vaux Brewery scheme proposed for Sunderland. Tom McCartney considers it vital that an independent team should set a high standard before a developer is invited in to build out the scheme because if you work with the developer from the outset a different agenda can take precedence. He also concluded that certain factors are needed if high density schemes are to be successful and provide user satisfaction.

These include high quality design which has been properly thought through, although this does not mean that the built project has to be expensive (good design is achieved by appointing good architects and locking the quality of design into legal agreements); accessible and reliable public transport; good and accessible local facilities and services and effective housing management systems and when we build, let us work hard to get it right and think that we build forever.

The Vaux Brewery area of Sunderland,
and an impression of what the new high
density development will look like

Unfortunately Christopher Carvill of the Carvill Group was unexpectedly unable to attend the debate but the thrust of his presentation (made on his behalf by Patrick Clarke) was that there must be an emphasis on design excellence and quality construction. The concept of “high density” often implies cramming with damaged communities on a downward spiral. Whereas, in fact, high density living can be very satisfying and low density living can be problematic as it is often car-dependent and does not necessarily work for older people who may no longer be able to drive.

On the whole people are social beings and like being together so that low density is somewhat counter-intuitive. Arguments in favour of higher densities include sustainability issues, creating more diverse communities and the opportunity for a greater live-work balance.

Interestingly many of the Carvill Group’s developments require great sensitivity of approach as they are in the sectarian heartlands of Belfast which raises the importance of understanding the context of areas and the interface between them. Carvill has delivered successful schemes of over 100 dph and up to 350 dph in Central Belfast and one important facet has been the provision of both apartments and family homes in developments to create more balanced communities. Another valuable approach is to talk to the communities first and set up situations where local communities can talk together. The greatest resident satisfaction comes through achieving safety and security and attractiveness and local pride. If places are well-designed and well-maintained then everyone take pride in them and cares for them.

It is important to avoid the mistakes of the past and one way to do this is through study tours so that everyone involved in a project can gain confidence from understanding best practice examples and work towards the same standards. Developments should add to cities and not just to developers’ profits.

The importance of holistic masterplanning

Rory Brooke of the URS Corporation had the task of explaining the importance of holistic planning and ensuring the delivery of the necessary infrastructure to support higher density communities. The key to providing satisfactory levels of infrastructure is to assess needs, consider existing supply, identify any gaps and make recommendations for delivery. These issues need to be explored through a range of infrastructure requirements including schools, health facilities, open space and employment. Sometimes the solutions need to be sought outside the box.

For example at the Leamouth Peninsular development Ballymore are proposing to build 2000 housing units with a private school on site. The GAP analysis has shown that households buying into this development could afford private schools. The Millennium School in Manhattan rented three floors of an office block which it converted into a school as this was more feasible than finding a suitable school site in that densely developed city.

For healthcare the HUDU (Healthier Urban Development Unit) model promotes the health agenda and assesses the health infrastructure needed for new housing including mental health facilities. The necessary revenue funding could be achieved, for example, for, say, three years from developers as part of the Planning Gain package (Circular 505).

Housing Density Matrix

Holistic planning means that it is important to integrate the social infrastructure to the high density masterplan. The Housing Density Matrix originally developed by Patrick Clarke of Llewelyn Davies Yeang and recently reviewed by URS set bands of density linked to urban character and transport. An alternative to measuring density through dwellings per hectare (dph) is to use plot ratios of all users rather than housing density alone particularly for mixed-use schemes where more than 35% of floor space is non-residential. (There is no scientific basis for fixing on 35% but it seems to make sense for mixed-use developments).

In answer to a subsequent question on plot ratios, it was explained that central Paris has not been redeveloped not because of a strong conservation lobby but because plot ratio control across the whole of central Paris was lower than existing plot ratios, so there is no incentive to rebuild.

Summing up the day

In summary it is necessary to review and question the policy framework; to assess need for all social infrastructure and compare this with supply; to look at options for filling gaps both on and off site and to think laterally for alternative ways of finding solutions; to work with architects and masterplanners through an iterative process of adjusting densities and unit mixes to find the optimum for each development and to enter local engagement at the appropriate stage in the project.

In the final session Professor Drew Stevenson gave a key note address on designing the communities of the future. He set the stage by proposing that it is not possible to design communities at all but it is possible to help people to live better lives by trying to find the answers to four key questions:

  • who lives at higher densities and what are their likes and dislikes?
  • how are things changing?
  • what are the key issues for successful developments?
  • what conclusions can be drawn?

Who lives at higher densities? One person households, particularly single older men (SOMs); young people particularly in central and inner London (an earlier question had raised the question of whether there was an emerging demographic divide with over 35 year olds living out of London and under 35s living in London); black and minority ethnic communities; “urbanites”; trapped residents particularly long-term council tenants, the elderly and the poor and suburban leavers.

What are their likes? Having access to good facilities, public transport and parks as well as friendly neighbours. Dislikes included lack of consultation; crime and vandalism and being trapped at home especially the elderly, those with poor public transport or those who are fearful of crime. At this point Professor Stevenson dispelled some density myths such as the fact that there are no real links between density and overall satisfaction or anti-social behaviour or increased use of local shops. High density need not mean high rise and some of the richest people in London live in the highest density areas, for example the Royal Borough of Kensington and Chelsea.

How are things changing? People tend to form their values between 18 and 24 and hold these values throughout their lives. Values change through generations but not within a generation. Younger people are moving to London for the racial and cultural diversity offered in high density areas. They seem to be more independent and more tolerant of ethnic groups than their parents. Working from home and the emergence of the café society are good for high density developments. People will also accept smaller living spaces for central locations. Average densities in London, especially towards the north-east were 131 dph in 2005/6. There are also 2½ million jobs in London and so transport access to effective public transport is critical.

So what are the key issues for successful developments? The physical issues include the housing mix where there is a serious lack of 3-4 bedroom family homes for both private and social housing. In this regard Professor Stevenson emphasised that people (pph) or bed spaces per hectare are more important as a measure of density than dwellings per hectare. Unfortunately general standards such as internal space standards are controlled through Building Regulations and not Planning.

On the Continent the dwellings are bigger with more storage space, more clearly understood refuse and recycling systems, private balconies, properly managed open space and good access to public transport. Social issues include getting the social infrastructure right; providing the right mix of community facilities for all age groups; avoiding “entrapment” situations as it is hard to retrofit and create social infrastructure in existing areas; good design recognising people’s preferences for varied designs that fit into the urban grain rather than large developments with identical blocks; affordable service charges for social housing.

Management issues for successful schemes need to ensure that there are a higher proportion of older residents, fewer children, with a range of ages for resident children; mixed tenure developments and at least 35% of residents should be in full time or part-time employment. Encouragement to be considerate neighbours will help to achieve care of the communal areas. Drew Stevenson concluded that high density can work provided the key issues described above are properly addressed and people are consulted and involved so that they have a greater sense of well-being by being given greater control over their lives.

Lessons learned

It was interesting that density in itself is not a major issue since it can both work very well and fail very badly for reasons other than actual density.

It is clearly important that there is a holistic approach and every member of the “team” is following the same vision for the end user and also has an equal hearing in decision making. This includes policy makers, design teams, management teams, developers and investors and, of course, users so that the outcome is not driven by any one agenda. That said there are some agendas that should be non-negotiable and will provide both constraints and opportunities.

For example, the sustainability agenda where the requirements of environmental sustainability and climate change adaptation policies may conflict with other desires and aspirations. Common ground among all presenters included the importance of achieving high quality designs (It is interesting that this is at a time when CABE has shown that about 80% of buildings have no involvement from architects) and the importance of good management and aftercare for buildings, open amenity space and the wider public realm.

The overall message was that with thought and consideration we can avoid the mistakes of the past and build for the long term. Each presenter was able to show examples of clearly unsuccessful schemes and as Ben Page said, having put up an image of a particularly dire scheme, “Is this what we want to be famous for?”