Eminent Ground: tall buildings in the city

The arguments and counter-arguments for the protection or the development of the urban skyline have become a central aspect of the debate regarding the future evolution of our cities. While there are number of cities in which urban form and tower form have developed a successful symbiotic relationship - New York, Chicago, Hong Kong and Singapore - and there are also instances, as in Yemen, where local vernacular tradition has evolved a fusion between the city block and tower - in contemporary Europe the integration of tall buildings into the streets of our cities remains problematic. The debate in the UK has tended to focus on three issues: on the perceived threat of the tower typology itself, on the impact of towers on the skyline and on the relative merits of different rationales for their location. If one accepts however that tall buildings are inevitable components of our major cities, driven by land values, public transport accessibility and accommodation shortage, what becomes really important is how towers are integrated into the fabric of the city and the quality of the places that they make at street level.

While the processes that define the location of tall buildings at the macro scale are largely out of the hands of architects, the task of embedding these forms into the fabric of the city – its streets, squares and lanes – at the micro scale, falls squarely within the realm of architectural practice, contingent as it is on the scale of the human being, public space and movement.

Just as the architect defines the form, profile, material and detail of the building, determines the organisation of the plan, tests the building for environmental impacts such as wind and overshadowing, so the architect has to take responsibility for integrating the building with the city at its base.

The relationships formed between the building and the public realm – the configuration of the building envelope, the location of entrances and cores, the selection of ground floor uses and the accommodation of service requirements (delivery bays, car park entrances, refuse storage) – are an essential aspect of its integration with the city. The location of the cores, for example, interlocks the vertical figure of the tower to the horizontal patterns of movement and public spaces of the city. In respect of this civic responsibility it is not enough that towers should be shapely and beautifully clad; they must also support the logic of the existing urban fabric and provide relevant ground floor relationships. They should facilitate, rather than frustrate new connections and, when possible, form the edges of public spaces, stimulating and supporting civic life. The way in which these relationships contribute to the quality and coherence of the city now defines the critical territory for the design of tall buildings.

The indisputable prominence that tall buildings enjoy has led many urban commentators to conclude that tall buildings should be treated as landmarks in the city, signifiers of concentrated activity or key locations and to argue that the architecture of towers should be developed accordingly. There is however an alternative position which seeks to draw tall buildings into a closer relationship with the urban fabric of cities and, whilst acknowledging the importance of their visibility from a distance, accepts that at ground level they may benefit from a less assertive approach. What this implies is that tall buildings might assume a more modest role within the city: the idea of a tower as part of a differentiated yet continuous urban fabric rather than as an individual set piece suggests the possibility that tall buildings might be considered as ‘background’ elements rather than primary figures of the cityscape.

Exactly this approach can be found in many Italian towns and cities. The Romanesque campanile of Lucca bristle above the town in brick and stone, dispersed, not clustered, orientating citizens to its various parishes. Narrow converging streets frame the campanile of San Frediano set in a small public space behind the basilica. The campanile of San Marino is embedded in a corner of the Piazza Di San Marino, terraced to one side with the great duomo and to the other with secondary buildings that together form the edge of the piazza, whilst the Torre Guinigi is differentiated by a rooftop garden of mature oak trees. Each is both a legible, grounded volume and a component of the city fabric, forming the edges of streets and piazzas, growing from the everyday bustle of terraced buildings. Whereas in Pisa the famous circular bell tower stands alone, acting, like the baptistery, as a foil to the duomo, an isolated statement in a loosely defined open space orientating the people of the city to its religious heart, in Lucca the tower is both subservient to the space it addresses and continuous with the city fabric, pointing to a model for dense urban centres. In contrast, the Pisa model finds its echo in the idea of the ‘iconic’ tower – the eminence that sets itself apart.

In London the towers of St Mary Axe by Foster + Partners and the Shard by Renzo Piano provide a similar contrast, one a free standing building, circular in plan, standing within a site opened up to receive its idealised form, the other a complex plan shape, continually adjusting as it meets the ground and thereby capable of establishing a relationship with the complex urban fabric – streets, station platforms, railway viaducts – that form its context.

At the Shard two distinct techniques of urban integration are evident. The first is the erosion of the floor-plates to create a transition of form from the base to the top, articulated through the tapering facets which slide past each other to align, define and enclose the public spaces. The second is the use of a mediating building – the Mini Shard – which both establishes a clear relationship with the main tower and shares the scale and typology of the surrounding building context.

The technique of the erosion or the evolution of building floor plates from one level to the next has been explored in a number of contexts. The stepping floor plates of New York skyscrapers enable a densely packed order of tall buildings to coexist. Each undergoes a transition from the discipline of the city block at its base to a proliferation of diverse accommodation above, benefiting from the resultant terraces and balconies as well as the articulation of the facades. More recently the capability to transform a tall building from one plan shape to another by incrementally adjusting its floor plates has been supported by digital technology and offers alternative possibilities for architects to respond simultaneously to ground level and high level conditions by twisting and tapering the form of the tall building.

The technique of using mediating buildings as part of a masterplan approach to contextualise a tall building is also exemplified by a New York precedent, the Rockefeller Centre. In this case the low rise retail buildings define a series of exceptional public spaces that both set it apart as a civic destination and relate to the scale of ‘Old New York’, creating a context in which the eminence of the main tower feels appropriate.

Other examples, by contrast, point to a condition where the tall building can be integrated with its context as a background element within a site masterplan or an existing city block. Our student housing scheme on Great Suffolk Street, London, places the tall element at the back of its site, close to a railway viaduct, rather than addressing the street. A terrace building forms the foreground element on the street and completes the perimeter block thereby cutting off lines of sight to the taller element from the immediate public realm. In a similar, earlier, example at One Kemble Street in Covent Garden, Richard Seifert situated a tall cylindrical office building at the corner of two secondary streets off Drury Lane, behind a block that occupies the primary, Kingsway frontage and continues the level of the street frontage established by its nineteenth-century neighbours. In this case the placement of the tower not only allows the urban continuity of Kingsway to be respected but also secures the continuity of the city block, despite the use of the circular plan form.

As cities embark upon a new wave of tall building developments it is essential that we develop a greater understanding of the role that tall buildings play and recognise how their ground floor relationships and the routes and public spaces they create can make more positive, long lasting contributions to an ever more thriving context for city life.