Rethinking urban density

Density in urban development refers to the concept of concentrating buildings and all associated infrastructure to service them. Density’s two key objectives are:

1. Efficient quantity – optimised resource use (land / materials / energy / services)
2. Efficient quality – improved spatial values (privacy / health / community / character)

National and international policy guidance, and various academic research have over decades covered density for new and regenerative urban development, particularly. Most of these are very useful, particularly the 2024 Sustainable Residential Development and Compact Settlements and the 2018 Urban Development and Building Heights guidelines.

The built density of our urban environment affects our social life and economic performance. The very reason why we built cities and towns and why these keep growing is: to participate in social and economic activities, in the safest and most convenient manner. Building dense is economic land use, in optimised built form while reducing unnecessary land cover, use of resources, and travel distance to a minimum.

Ireland is facing increasing demand for high quality living in dwellings that are affordable, central, suitable, and diverse, when household sizes are shrinking. Ireland is also facing increasing pressure to reduce resource consumption and GHG emissions. The logical response, backed by best practice examples and policy guidance is increasing urban density, in central locations, with quality public transport access, and appropriate to existing surrounding built form and scale.

This approach includes the critical review of existing development, where density does not meet the requirements of resource efficient land use, transport infrastructure and services. Densification here would secure the performance standards of these places into the future. Successful places (Jacobs 1961) are characterised by a healthy balance of the following four spatial qualities:

• Density
• Diversity
• Distinctiveness
• Connectivity

Throughout the 20^th century, Ireland has experienced drastic social and physical changes. A lifestyle evolving around private car use has shaped our cities, towns, and landscape.

Our previous planning culture has supported this trend by policies and practice for suburban sprawl and hinterland development while historic town and city centres declined, in population and socio-economic activity, hence becoming less safe and attractive places to live, work and socialise. Increasing density in our centres will break these vicious cycles and will reverse negative trends towards virtuous cycles.

Densifying existing neighbourhoods should be applied with caution, and with the objective to heal communities that have been severed by car dominated transport corridors and are disjointed by missing critical mass to activate land (Engwicht 2007). Therefore, a mix and balanced distribution of uses, sustainable mobility, responsive built form and quality public realm are paramount.

Applying density is a just tool to generate a critical mass for sufficient footfall, ideally 24/7. This footfall alone will create safe and attractive urban centres, make public transport and critical infrastructure efficient and will support successful placemaking. If we don’t manage to bring more population back into our cities and towns, their decline will continue.

Vacancy and dereliction will increasingly scar our urban centres, making them feel unattractive, unsafe places to live, work, visit and invest. It should be noted that the Irish Government has introduced supportive policies and funding for the regeneration of our urban centres, foremost the Town Centre First Policy, the Town Centre Living Initiative and the Croí Cónaithe (Cities) Scheme to bridge the current ‘viability gap’ between construction costs and market sale price of apartments. The Heritage Council and the RIAI have contributed further useful initiatives.

Density in Ireland is mainly measured in DPH (dwellings per hectare). While this measure might be suited for assessing suburban land capacity and general built form (detached / semi-D / terraced), it remains one-dimensional when it comes to floor space and occupancy. 40 DPH 2-bed houses generate a very different density to 40 DPH 4-bed houses.

Number of bedrooms appears an outdated measure when it comes to smart urban development, predominantly in apartment form, to comply with sustainable development targets.

Hence, plot cover and plot ratio appear to be a much more suited measure, to calculate demand, supply and certainly building and occupation and maintenance costs. The European continent has applied this approach successfully for decades and applies it across board for the mix of use a city or town would display.

In public discourse, density is often perceived synonymous with high-rise development, yet need not be, as recent residential developments in Dublin and Cork demonstrate. Very efficient density can be achieved with less than 10 storeys, while providing excellent quality (light, privacy, health) and a congruous response to scale and form – here, Paris and Milano are two leading example cities, among many others.

Developments of semi-detached and terraced houses achieve a density of 40 DPH max., an insufficient critical mass to support economically viable streets, public transport, green, services and facilities. Best practice illustrates how higher densities, in form of mixed town house, duplex and apartment arrangements work well, and pay for all required infrastructure.

Nonetheless, the economic paradox that building apartments is financially not viable for many private developers, while building houses at suburban scale is, has not yet been unfolded. Amply available, affordable greenfield sites being more attractive than expensive urban sites is only one part of the answer.

According to CSO figures, only 26% of units completed in 2024 were apartments, leaving 74% to the housing market (CSO, 2024). A market supplying a traditional demand drives this trend, against national and local policy guidance: People still want a house, no apartment – full stop!

It comes down to the preference of own door access, which is comprehensible and needs to be reflected in the supply. The solution lies in the creative design to provide such, either directly from the street, or via attractive, lobbied shared access that is perceived as a private address and entrance to a home. Compact own door houses, in duplex and triplex arrangement can generate densities of up to 100 DPH, achieving compact settlement targets.

Further to above-noted context, density is the prerequisite to many of our current Compact Settlement models, such as the 15 Minute City / 10 Minute Town concept, Town Centre First, Low Traffic Neighbourhoods, New European Bauhaus, Nature-Based Solutions.

All these have in common that buildings and facilities are used much more efficiently, often shared, and journeys to work, school, to shop and socialise, to exercise and enjoy culture, to avail of public and medical services are only a short walk or cycle, with quality public transport to avail of nearby.

Without a doubt, Ireland’s built environment will have to become denser to meet our legally binding Climate Action Plan targets!