Dublin's
Density Targets
Dublin's density is a complicated story. With a reputation of a low-density city, Dublin has neighbourhoods that are some of the densest in Europe. Where should density be increased and how can this be done sustainably?
WHAT DENSITY DO WE HAVE?
In Ireland there has never been, to our knowledge, a mature, researched assessment to establish what exactly a sustainable city or town looks like or means.
Policy has been to let the market decide what works. As well as the headline density of the entire city being 4,820 people per sq.km., (which compares well with Amsterdam, for instance, which has far better infrastructure than Dublin), some city wards have densities in excess of 23,916 p/sq.km.
Dublin’s historic urban core is not specifically in need of densification.
The 2016 Census showed that Dublin City’s population was 544, 544. Its area is 116 square kilometres and it had 240,553 households. The same Census counted the population of Dublin City and Suburbs, with an area of 318 square kilometres, at 1,173,179 in 468,372 households.
DUBLIN'S DENSITY TARGETS
The National Planning Framework predicts an increase of 235,000 to 293,000 people in the city and suburbs by 2040. Given that their definition of Dublin city and suburbs conforms to that of the Central Statistics Office, with a land area of 318 sq.km., this means an increase in density of between 740 to 920 people per square kilometre.
For Dublin City, The Regional Spatial and Economic Strategy predicts 100,000 additional inhabitants by 2031. At an area of 116 sq.km., this means providing for 860 more people per square kilometre. In Part 1 of the Pre-Draft Development Plan 2022-2028, "Context", Dublin City Council foresees between 58,000 to 70,000, which means an increase of between 500 and 600 people per square kilometre. The current population of Dublin city (2016) is 554,554 – a density of 4,800 people per square kilometre. This means an increase of 12.5%, resulting in a density of 5,400 p/sq.km.
There are future projections of 400,000 plus, so we should probably over-plan for increased numbers. Added to the population projections are the demographic changes, which will affect the number of homes needed in the future.
There are so many variables in measuring or programming that density that it is impossible to have a “one size fits all” target. It depends on geography – Sea, mountains, rivers and lakes, for instance might determine the “habitable area” of a place. It depends on infrastructure such as transport, water, waste treatment, hospitals and schools, for example, both current and planned.
It depends on topography, which is the arrangement of natural and artificial physical features. For example, in Dublin City, parks and the Dublin Port take up 23 of the 116.6 square kilometres of the area of the city – the Phoenix Park alone is more than 7 sq.km. In the suburbs, there are large parks, industrial areas and the Dublin Airport alone occupies 10 square kilometres. Roads, canals and other surface features occupy land areas that impact on the measuring of density.
Dublin Airport, Port and Parks
Measuring Density
If you measure in Units per Hectare (UPH) you will have net and gross densities. These two maps illustrate the difference. The first one measures the density in UPH of two-storey houses along the River Dodder. This gives a “gross” measure of 155 UPH. The second map measures a wider area, so that it includes open space, roads, rivers, linear parks, etc. This gives a “net” measure of 38 UPH and includes localised developments ranging from 25 to 120 UPH “gross”.
We can see that using Units per Hectare can be quite misleading. When we add into the equation occupancy rates, the figures get even more variable. At present, the average occupancy of a home in Dublin is approximately 2.4 people per unit. If that figure drops, we need more homes. If that figure increases, we need fewer homes.
Population and demographic trends also crucially impact how we measure use and need.
The dwelling unit type also affects density. For example, one two-bedroom home might have the same population density as two one-bedroom homes. So, the type of housing also matters in how we measure and plan density.
Taking all these and other factors into account, the best measure of density is population density – the number of people we need in a given area to support sustainable communities. This is the basis of the “15-Minute City”. There appears to be general consensus that a population of 25,000 aligns with the “Sustainable Neighbourhood” put forward by many and the 2002 Goodbody report that that figure was needed to sustain public transport.
The 15-Minute City
Walking, the 15-Minute City means a diameter of 1.25 kilometres. This gives an area of 5 square kilometres. With the “sustainable” figure of 25,000 inhabitants, this gives us an “ideal” density of 5,000 people per square kilometre (ppkm2). We can see from the 2016 CSO statistics that Dublin City has a density of 4,800 ppkm2, so our 2016 density was approaching a sustainable level.
For Dublin City and Suburbs, the 2016 density was 3,700 ppkm2, some way off the ideal. If we could raise this figure to 5,000 ppkm2, we could accommodate a further population of over 400,000.
For the RSES projections for the population of Dublin City to increase by 100,000, we will need to increase the density by 860 ppkm2, giving an overall density of 5,660 ppkm2. It would, in our opinion, be wise to plan for 6,500 ppkm2, to allow for further compact growth, or more open space, if the growth does not materialise.
In translating this data into how many new homes we need in the city, we should take account of demographic changes, which will impact on the occupancy of the existing and new building stock.
All of this indicates that densities should range from 65 to 100 UPH – and higher where appropriate in the context of a specific site’s size and context - whether that be through the re-use of existing buildings, the development on underused infill sites, the regeneration of existing neighbourhoods and the development – where appropriate - of serviced greenfield sites. This could be achieved on the city’s zoned lands, as well as the surrounding suburbs.
Appropriate Buildings
A key issue is defining the appropriate built form for any particular location. The lower street-based models – from three to six storeys – balance density with streetscape quality, and open space with residential amenity. Being more economical to build and maintain, it is therefore more affordable. Point blocks make for generally less-successful streets and public spaces, they create wind and microclimate issues, and their internal corridors are less conducive to the development of social capital. It is exponentially more expensive to build and maintain, and therefore outside the rental or purchase range of most salary earners.
The recently published Housing Design Handbook by David Levitt and Jo McCafferty is an excellent source of information on both residential densities and best- practice exemplars. The case studies it contains indicate that net densities of 65 dwellings per hectare can be achieved in three-bedroom terraced townhouses, and at two and three storey heights.
Bristol - a city with a population of 693,552 and an overall density of 3,900 ppkm2 - permits densities of 50 dwellings per hectare only where it is essential to safeguard the character and special interest of a historic location. Elsewhere, the optimum densities recommended in its Urban Living SPD (Supplementary Planning Document) range from 100 UPH in urban areas to 200 UPH in the city centre. By comparison, in Planning for Less Car Use, Friends of the Earth recommend densities of around 100 UPH, and higher in city centres - accompanied by ‘clear design guidance to ensure that housing quality, character, mix and sense of place are protected and enhanced.’
What the long-term impact of the Covid-19 Pandemic will have on the way that we live and where we live is yet to be analysed. However, it may have a major impact on the way that we use our cities.
Gross density (155 UPH)
Net density (38 UPH)
DUBLIN’S DENSITY COMPARED TO OTHER EUROPEAN CITIES
There is a view that Dublin is a low-density city and that we are somehow equivalent to Los Angeles in terms of “sprawl”. To put this in context, Greater Los Angeles has an area of 87,940 square kilometres; our entire country has a land area of 70,273 square kilometres. The frustration of the commuter, badly served by public transport, stuck in their car every day, is understandable, but it should not colour our perception of reality. Dublin is not a low-density city.
At 4,800 people per sq.km., we are not out of tune with the European cities that we admire. We are denser than Berlin and Bristol (3,900 ppkm2), Vienna (4,326 ppkm2) and Manchester (4,680 ppkm2). We are similar to Stockholm (4,900 ppkm2), Sevilla (4,900 ppkm2), Amsterdam (4.994 ppkm2), and Madrid (5,200 ppkm2). We are behind London (5,432 ppkm2), Copenhagen (6,900 ppkm2), Barcelona (16,000 ppkm2) and Paris, with its extraordinary 21,000 ppkm2.
All of these cities to which we aspire are low-rise, with careful urban planning to the scale of the inhabitant. They do not overpower or overdevelop their places. Unlike Dublin, they have already invested in infrastructure such as high-density, high-speed transit systems. In Dublin, we appear to paint white lines on existing roads and call that transport infrastructure. These other cities have built the capacity that allows for higher densities.
Inspired by Ebenezer Howard’s Garden City theories, the default 12 houses per acre model on which Dublin expanded from the fifties onwards delivered the densities found in most of the city’s middle-class outer suburbs.
Despite Howard’s ’there’s nothing to be gained by overcrowding’ philosophy, numerous European projects over the past decades have illustrated that there is little to be feared from higher densities. Bo01 in Malmö, Vauban in Freiburg and Hammarby in Stockholm are excellent examples of sustainable urban expansion. All are mixed-use, but predominately residential; all employ state-of- the-art water, waste and energy infrastructure; all have urban structures that promote walking and cycling; all have high quality landscaped open spaces; and all are generally no taller than five floors.
As seen from the figures above, population density is the only empiric measure of how densely populated are neighbourhoods, towns or cities. Population is the ultimate measure of vitality, vibrancy and viability.
Marino, Dublin
THE DIVERSITY OF DUBLIN’S DENSITY
Dublin’s density, like many other cities, is very variable. Below the headline figure of 4,820 people per sq.km., lies a wide variety of scales, densities and layouts.
Some of the most desirable places to live in the City are very dense enclaves that have little parking and small measures of private space. The outer edges of the city boundaries have population densities of between 3,000 – 4,000 ppkm2. Areas closer to the canals have densities between 4,000 – 6,000 ppkm2. Areas such as Crumlin and Marino are in the order of 7,500 ppkm2 and some of the most populated areas, such as Kilmainham, Potrobello and Stonetbatter, all within the canals, reach 10,000 ppkm2 or more. The most compact area of Dublin City is the Rotunda Ward, with a population density of 23,916 ppkm2.
The pursuit of higher density development today is driven by the universally accepted truth that compact cities and towns are more sustainable - economically, environmentally and socially: infrastructure and services, including public transport, are more viable; private car-use and air pollution are reduced as density increases; social capital and public health are enhanced as people have access to a greater range of facilities and amenities within walking distance of their homes.
The Pre-Draft issue of the Dublin City Development Plan 2022-2028 notes at 2.6, “The emphasis of the current City Plan is that Dublin City is fundamentally a low rise city and that there is a need to protect and enhance the skyline of the city and ensure that all mid-rise and taller buildings make a positive contribution to the urban character of the city and prevent visual clutter of the skyline.”
It also notes that: “The key challenge in the new city plan, therefore, will be to ensure that the future densification of the city takes place in a managed way to ensure that sustainable communities and neighbourhoods are fostered and that such development is delivered in tandem with the necessary social and physical infrastructure. The plan must provide for opportunities for increased density and height in a sustainable way, in a manner that contributes to compact growth whilst ensuring the highest standard of design and the protection of existing amenities and the natural and historical assets of the city.”
