How dense is too dense?Build up, build out – Brighton's need for new housing must have rational answers, writes David Robson.
We live in the most densely populated country in Europe – our towns and cities already cover around 15 per cent of our land. In the face of an unexpected surge in population and a shortage of affordable housing, we have to find ways to build within existing conurbations and we have to build to higher densities if we are to protect our shrinking countryside.
Nowhere is this more true than in Brighton, a city hemmed in by the Downs and the sea, where little land is available for building and where the council is under pressure from government to commit to ambitious housing totals in its new City Plan. But all of this begs a question: what densities are feasible, what densities are compatible with healthy and happy living? How dense is too dense?
We can measure density in terms of dwellings per hectare but it’s more meaningful to consider bedspaces – the number of dwellings multiplied by the number of theoretical bedspaces that they contain, which gives a more accurate indication of the potential number of occupants. We can also measure density in terms of floor-area-ratio or FAR, which measures the area of a building against the area of the site on which it sits.
Gehry's King Alfred plans: too tall?
One of the problems with the failed King Alfred development in Hove was that the city, which owned the land, failed adequately to assess its capacity in terms of either bedspace density or FAR and issued an unrealistic planning brief which was little more than a shopping list. As a result, the developers were encouraged to put more on the site than it could reasonably accommodate.
Brighton exhibits densities which range from as little as 40 bedspaces per hectare in outer suburbs such as Westdene to 500 bedspaces per hectare in the tight grid of Southover. High-rise flats built between the wars, such as seven-storey Furze Croft in Hove, achieved densities of around 600 bedspaces per hectare, densities that have rarely been exceeded since. This range of densities implies huge inequalities in terms of amenity and environment.
Of course, increasing the density saves land and reduces the cost of infrastructure and services but studies have shown that once densities exceed 400 bedspaces per hectare, a law of diminishing returns sets in.
Anson House: a wasted opportunity
A given population still needs access to open space, schools, shops and other facilities, while increases in residential density produce diminishing overall savings in land.A reasonable hypothesis suggests that densities in excess of 600 bedspaces per hectare are undesirable in terms of social and physical well-being and achieve only marginal savings in land.
As density increases, other factors take on a heightened significance. An increase in the number of dwellings produces a corresponding increase in the number of parked cars, prams, wheelchairs and bicycles as well as quantities of waste. It is salutary to note that 100 parked cars need an area of about 2,500 square metres.
More people put additional pressure on a diminishing area of open space and include more children who need play space and more old people who need a seat in the sun. And high density living leads one to reconsider space standards within the dwelling and the need to provide adequate storage and useable balcony space.
Then there is the question of height. Should we build tall and thin or short and fat? A development with a footprint of 50 per cent and a FAR of four will require an average height of eight floors; increase the height to 16 floors and you reduce the footprint to 25 per cent, freeing more of the site for landscape and increasing the space between buildings. People objected to the first Gehry scheme for King Alfred on the grounds of its excessive height but the second scheme, although lower, was far bulkier, more obtrusive and less attractive.
In considering recent proposals for the Anson House site and Circus Street, the Regency Society has concluded that there is a need for a city-wide debate about development parameters. What floor-area-ratios are appropriate for different sites? What height restrictions should be imposed? What bedspace densities are feasible? What dwelling mixes and space standards should be adopted?
When a major planning proposal fails, this should not be a cause for rejoicing. Each proposal involves a huge investment in time and resources and failure means that valuable land remains fallow. The fact that so many schemes have failed during recent years suggests that it is time for the council to review its planning strategies in order to ensure that targets are realistic.
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