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The Density Debate – A Personal View Christine Whitehead London School of Economics and Cambridge Centre for Housing and Planning Research East Thames Housing Group The Building Centre London 24 January 2008 . How Do We Define Density?.

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The Density Debate –

A Personal View

Christine Whitehead

London School of Economics and

Cambridge Centre for Housing and Planning Research

East Thames Housing Group

The Building Centre London

24 January 2008

How do we define density
How Do We Define Density?

Density is defined very differently by planners and


  • Planning densities are defined in terms of physical attributes – numbers of dwellings or habitable rooms per hectare;

  • Economists are interested in outcomes in terms of population per hectare and densities of occupation;

  • The two are usually related to one another but not always; the relationship is changing; and sometimes inconsistent

Why are we interested
Why Are We Interested?

  • Important element in the debate about whether planning policy is too constraining and whether the emphasis on density is helping to increase prices;

  • Regarded as a core element in the sustainability and regeneration agenda;

  • Strongly related to other policies notably on brownfield development; Section 106; and mixed communities – but the linkages often not understood

Government policy on densities
Government Policy on Densities

  • Requirement to increase residential planning densities placed on regions and local authorities;

  • Formal requirements in PPS3 (2006) actually no tougher than those in PPG 3 introduced in 2000. But the rhetoric and the pressures put on authorities much stronger;

  • Interpreted differently in different areas but generally the pattern is based on location in relation to the centre and on transportation. Little emphasis on other aspects of sustainability (assumed able to respond);

  • London’s policy in the London Plan very much stronger than anywhere else in the country – with major implications for the size of dwellings and built form

Actual densities
Actual Densities

  • Outside London, densities have been falling – in suburban as well as central areas;

  • In London immigration and population growth have necessarily increased densities;

  • Densities of occupation vary greatly between different groups of households; between tenures; and most importantly by income;

  • Location and space per dwelling are highly correlated with one another, in part because of their relationship to income distribution

Fundamental tensions
Fundamental Tensions

  • In a growing economy demand for housing increases roughly in proportion to income growth – so if incomes rise by 2% p.a. for twenty years we want about 50% more housing overall;

  • As supply is constrained this pressure increases house prices; differentially increases the price of larger units; and increases problems of affordability at the bottom end of the market;

  • Role of planners impossible? Must aim to use less land; build on more brownfield; achieve mixed communities; provide more space per person; provide more units; ensure better design; and improve quality and services for both

    additional and established households

Economic principles of planning
Economic Principles of Planning

  • Economic rationale for planning is to overcome market failures – encourage positive externalities and discourage negative; improve information; assist adjustment; and ensure adequate provision of public open space and services;

  • Higher densities address issues of urban sprawl and the need for diverse and productive economy – but also costs of too high densities in terms of pollution, congestion and the loss of value to individuals;

  • Fundamental objective to maximise social value of development – but while general objectives are clear, relationships are complex and target based approaches may produce perverse results

Market pressures
Market Pressures

  • Demand for separate units increases with demographic growth but equally with incomes across established as well as additional households;

  • Income elasticities similar for internal and external space – and stronger for houses than flats;

  • Also evidence of pressures to live closer to the countryside – but value of local open space particularly high;

  • Some types of household value central locations and newer migrants generally demand less housing per household;

  • Given a growing economy one would expect to build at high standards suitable for the future and to allow older/less appropriate housing filtering down the system

The evidence in densities
The Evidence in Densities

  • Population densities fell significantly from 1945 up to the 1980s. They stabilised in the 1990s (1% decline) while densities in London actually rose by 8%;

  • This is partly the outcome of constrained supply and rising prices;

  • England’s urban areas are relatively dense as compared to other high income countries – except for central London;

  • On wider definitions of London, densities are high by international standards

The evidence on sustainability
The Evidence on Sustainability

  • The most quoted estimates that doubling density halves energy use is based on a simple correlation and reflects stage of development rather than a direct relationship;

  • Corrected estimates show an impact of well below 10% and would involve quite unrealistic policy constraints;

  • Higher densities support better public transport – but the critical figures for this are between 25dph and 60dph ;

  • The position with respect to local services – and healthy living – is even less clear – but again 50-60dph appears to be the relevant benchmark

Do higher densities deliver
Do Higher Densities Deliver?

  • Higher densities traditionally generate more but shorter trips, using more public transport

  • Evidence from the “revived” central urban areas such as Leeds suggests that as individual networks expand these trips are getting longer

  • The growth of second and weekend homes is also relevant here as, if people have less space in the urban area, they substitute other (less sustainable?) lifestyles

  • The most important issues are how the demand for space can be satisfied and the ways in which the construction industry is responding to market and policy pressures

The policy response
The Policy Response

  • Rapidly increasing planning densities;

  • Smaller units with less space per room;

  • More flats;

  • Inflexible built form;

  • More shared ownership rather than social rented dwellings

Outcomes completions

  • Rising planning densities but stable or falling actual densities outside London;

  • The London phenomenon – densities rising for new construction 50% faster than elsewhere;

  • A massive change in dwelling composition linked to declining space standards;

  • Increasing reliance on one and two bedroom flats often with no through ventilation;

  • Is there a gap in the market provision of small units?

  • Are we actually adding to the total stock measured by space?

  • Can the mixed communities agenda operate?

What do people want market evidence
What do People Want?: completionsMarket Evidence

  • Declining occupancy rates in owner-occupied sector even in face of rapidly rising prices; relative decline in the prices of small flats (supply v demand/distribution of income) – although new dwelling premium; even initially occupancy lower than planned;

  • Higher densities in the private rented sector – especially among those relatively new to the country; increasing overcrowding; rents still based on capacity to pay not quality;

  • Groups who like central/dense living – young; single; students; less established households; older people looking for services?

Survey evidence
Survey Evidence and time in the UK

People buying in the market want:

  • Houses rather than flats;

  • Larger rooms even if fewer;

  • Quality kitchens/bathrooms;

  • Flexibility

  • Privacy, private space and well managed communal space;

  • Access to shops, transport, and parking;

  • Energy and environmental efficiency;

  • Not to live in featureless boxes

What do social tenants want
What do Social Tenants Want? and time in the UK

  • More space and larger rooms;

  • Better and more storage – inside and out;

  • Houses rather than flats;

  • To avoid noise pollution and poorly managed/ used communal space;

  • Better design – flexibility; ventilation; kitchens and bathrooms;

  • Good maintenance and rubbish disposal;

  • Access to parking, shops and transport;

  • Adequate security

Attitudes to density
Attitudes to Density and time in the UK

  • Density as such rarely the issue except for those spending large proportions of time at home;

  • Those overcrowded in the home notice – and dislike crowding in the area more;

  • Conflation between density and high rise – in people’s attitudes ;

  • Concerns about interaction between new high density buildings and the established neighbourhood

Three examples
Three Examples and time in the UK

  • Vienna 1929 – Luxury Art Deco for the masses (50 sq m per unit and lots of services) – now 80% plus “known to the police”

  • China in 1990s – 7 sq m per person; 2007 28m2 per permanent resident for new construction; current government aspiration 100 sq m per unit

  • London 2007: Homes for nurses at St Thomas’ Hospital – 230 flats for 400 plus hospital workers in 5-20 storey apartment blocks mixed with 330 private flats in separate buildings

Conclusions 1
Conclusions (1) and time in the UK

  • Perceptions of density thoroughly mixed up with overcrowding; built form; location; and attitudes to the neighbourhood

  • Urban England remains relatively densely populated. Only very central areas have below average densities as compared to other richer countries

  • The benefits of higher densities are overstated and anyway depend on existing development far more than on new construction – especially if people move away because of higher density development

  • Only in central London is there a case for much higher densities

Conclusions 2
Conclusions (2) and time in the UK

  • Higher densities, and especially high rise must be associated with high quality design and better services. Even so they will only be suitable for relatively small groups of mainly better off households;

  • Within central London a case can be made for iconic; well-managed; high service charged, super density close to good open space, local services and transport;

  • If these attributes are forgotten the result is likely at best to be extremely poor value for money and at worst the slums of the future

Conclusions 3
Conclusions (3) and time in the UK

  • The case for increasing planning densities at the lower end of the density scale is strong in order to maintain efficient services. However to be successful this policy must be combined with better designed homes which provide more space per household and greater flexibility – so that people actually want to live there now and in the future