Tall buildings and the public realm

The love affair with tall buildings is undeniable. Initially very much a western society symbol of power and progress that started in the late 19th century, the tall building love affair has well and truly infected developing nations throughout Asia and the Middle East, for many of the same reasons. Keen to be seen as the new power-houses of the world, these nations are falling over themselves to build the biggest and greatest symbols of their city's and creator's success. However, do tall buildings actually make these cities better places?

I will leave it to the architects out there to debate the merits and attributes of the tower design itself. A tall building is very hard to hide, so the importance of getting it right and designing an object of beauty is paramount.

A common concern with tall buildings is the way the building relates to the street or ground level. Can you remember the last time a tall building was promoted by its relationship to the street? The promotional visualisations always focus on the impact on the city skyline or the bird's eye view of the tower. Too often the designers are so absorbed in the iconic form of the tower structure that the lower levels are designed as an afterthought.

Typically the ground level is dominated by blank walls, security grilles, service and plant rooms, and car park access ramps. Token provision of retail or commercial outlets to activate the street often fail due to poor siting, economic feasibility and microclimatic conditions on the ground caused by the building itself.

It''s not just the ground floor that is of concern. The lower levels of the building also have a vital role to play in activating the street. Studies have shown that beyond a four to five storey height the occupants of the building lose their connection and interaction with the street. When these lower levels consist of car parking podium levels, the effect is obviously detrimental.

In relation to the Australia 108 tower, Melbourne Mayor Robert Doyle said: "We've got to keep an eye on where we want area like Southbank going. We don't want a canyon of enormous buildings with no life at street level."

Common problems with the public realm around tall buildings include:

• Restricted sunlight
• Exacerbated wind conditions
• Lack of activation at ground lower levels resulting in poor safety and surveillance
• Poor contextual response

But these can be tackled with good landscape and urban design.

Wind Conditions

Tall buildings are known to exacerbate wind conditions at street level, often causing very unpleasant and potentially dangerous micro-climatic conditions. Early engagement with wind modeling specialists is vital before the building design has gone too far. The modernist box may need to be relaxed if we wish to create a public realm that people can enjoy without the buffeting effects of the wind. It is about being contextually appropriate to the conditions and location of the proposed tower. Strategic planning should also look to address wind issues and determine what the collective result of many tall towers in a precinct may be.

Apart from the form, orientation and permeability of the building itself, the public realm can be designed to further ameliorate wind conditions at the street level. Canopies of trees or structures around the base of the building can help disperse winds; pathways can be directed away from specific spots that modelling suggests will be highly wind prone, shrubs and screens can create protected areas.

Active Edges

The most successful public realms and streets in our cities are those with mid-rise buildings providing a near continuous building frontage that supports an active street life.

In contrast, tall buildings that sit as freestanding objects in a plaza (think Le Corbusier) seek to remove themselves from city and street life with the result being soulless spaces that no one spends time in. Developing cities in the Middle East and Asia continue along this disastrous path.

The failure of the freestanding object in a space is obvious when one considers that buildings need to have areas for services, car park access, and other non-active uses. A building in a plaza has nowhere to hide or ability to place these out of view.

A hybrid solution exists whereby the tower is placed on a podium which creates built form at the street level of a human scale and form. The podium however must contain active uses ands access for the public, not simply at ground level of retail with levels of car parking above. This solution still allows the tower component to be a creative and unique design. If the tower is setback from the podium, the podium can also assist with wind amelioration. Service areas should be located on side or rear lanes.

Restricted Sunlight

Very simple and effective tools now exist to measure the effects of shadow caused by tall buildings. Using these tools early on in the design process is of great benefit. Towers should be slender and aligned to allow light into public gathering areas. The number of tall towers in an area should be carefully monitored so that the collective result is not detrimental. Strategic Plans should be prepared for precinct undergoing this type of development pressure so that this impact can be understood.

Undoubtedly, increased shadowing will be an inevitable result of tall building. Public realm design must respond to this and consider such things as plant and tree selection for these conditions, creation of public space where it can be modeled that sunlight will be captured, especially during peak times (ie lunch breaks), use of lighter coloured materials and potentially artificial lighting.

Understanding where areas will be heavily shaded should also determine the location of active ground level uses. Retail outlets typically prefer a sunny outlook. Don't waste sunny aspects on car park ramps, service areas and blank walls.

In very hot climates, the reverse situation to the above might be true. Public realm design in some Middle Eastern cities seeks to take advantage of the self shading caused by buildings to ameliorate the temperature and provide for more pleasant pedestrian conditions.

Contextual Response

Neighbourhood character is a dirty term where tall buildings are concerned, specially when proposed in areas previously devoid of such structures. How for example, does an area like Fishermans Bend in Melbourne successfully transform from a low-rise industrial area to a suburb of tall residential towers? Within the central CBD's of most cities it is a different story, where the tall tower is the accepted form.

For places like Fishermans Bend, a structure plan is essential that sets out the scale, form and uses of future development. Allowing open slather could result in 50 storey or greater towers across the entire area creating many of the problems outlined earlier in this article. Design and planning principles must be established such as ensuring towers are placed on or behind human scaled podiums, that building frontages have active edges including doors and windows, that floor levels respond to the public realm, that service areas are placed away from the prominent street frontages and many of the other suggestions already outlines in this article.

However, even these aideas may still result in a development that is largely out of context with its surrounds. We can either accept that this is an inevitable outcome of urban development or perhaps take a more radical (perhaps more conservative) approach that seeks to adjust the character of an area more slowly over time.

The first few tall buildings in an area like Fishermans Bend will vastly alter the area's character. What if instead, the first number of buildings are only allowed to be say, 20 storeys and then gradually over time as more and more is developed, this height limit be increased. This is really not so different from how the Melbourne CBD has evolved and allows the city and its inhabitants to embrace this change with less angst.

The unifying element in all this is the public realm, which fills in all the spaces between and around these tall buildings. Melbourne is much more defined by its great streets and lanes than by its tall buildings. If we want these streets and lanes to remain as a defining element of a livable city, then we must be very careful that our love affair with the tall building does not destroy them.

Jon Brock is National Director of Land Development at Meinhardt, a multi-disciplinary engineering and professional technical services consulting firm with a strong presence in the Melbourne and Australian market.