I used to think that a city is made up of buildings, people, utilities, social and political relationships, communication networks, green areas and so on, and that its limits are visible and recognizable. Later on, it became clear that a city has an extended area of influence, derived from complex territorial relationships, administrative borders, long distance transportation routes… But only recently I read a study on Hong Kong from the perspective of food consumption in relation to the city [1]. Seen from the perspective of the surface needed to grow food for its inhabitants, a city’s surface grows beyond visible and administrative territories, expanding widely…

The calculations state that for a city of 1.000.000 people, with a density of 300 persons/hectare, that determine a occupied surface of 3333 hectares, a surface of 1.500.000 hectares is acctually needed to grow food. This is a diagram made to envision the difference between built territory and the surface needed to grow food, for HK…

HK area necessary for food

… and it made me think about growing a roof garden. I also tried to calculate my carbon footprint for the first time, and it seems that all the bicycling I did this summer doesn’t compensate for the heating system I’m currently using.

[1] – Brenda Vale, Rober Vale. Is the High-Density City the Only Option?, Designing High-Density Cities for Social and Environmental Sustainability, by Edward Ng


The growth of population is currently one of the general global issues, its severity being increased in relation to resource depletion. From the perspective of the continuous growth of population, generating built environments capable of housing the entire population and adapted properly to the context is a major challenge of contemporary architecture. Proper relationship to a dynamic context in which the social, political, environmental and economic components are constantly changing is even a greater challenge.

However, density as unique criterion for generating built environment and urban quality has limitations. General attitudes towards high density architectures so far are dual. The positive arguments take into account the rational use of urban land resources, in relation to maintaining a compact urban and infrastructure development, with minimal impact upon the surrounding rural and natural areas, with efficient use of urban transportation systems and fuel resources. Also, areas including major population become themselves sources of variation and intensity, providing a very rich exchange of ideas, as Patrick Schumacher1 notices. On the other hand, negative implications arise in relation to the same urban components, identified by the congestion of urban landscapes, reduction of urban green areas and the occurrence of heat islands, deterioration of urban networks and traffic infrastructure by overloading, and not least an increase of psychological stress for the inhabitants.

Architecture is cyclically rewriting its formal and morphological language, generally as a counteraction to previous negative experiences in relation to context changes. In the past 30 years, constructions of large scale developments were accompanied by homogenization of the built product, resulting in maximizing the economic value of the project at the expense of social value2. Today, we are witnessing a new transition in the writing style of architecture, where the expansion of the built environment based solely on making a profit and speculative investments becomes abandoned by the manifestation of the recent economic crisis. Urban societies undergo a subtle transition in parallel, due to jobs migration from the perspective of the same crises and recent changes in family structure. The mononuclear monogamous family as it existed in the last century is no longer exclusively the norm. In relation to this background, new rules are needed for composing the built environment.

Architectural experience so far has shown that large-scale urban projects are generally incapable of long-term adaptation, generating urban and social conflicts and eventually being blamed in the end by being left empty. A design that vertically multiplies the same plan scheme or over determines constructions while looking for the perfect match of form and function is no longer viable in light of current changes. The main theme of contemporary design is relating to a constantly changing context. The process of urban development itself is a complex process constantly evolving, and the nature of contemporary urban life is very different from that of the traditional town, being more complex, heterogeneous, interrelated and dynamic3. For the contemporary city, consisting of a dense and varied overlapping of layers, information, populations, activities and relationships, a complex design strategy is required, able to incorporate all these components.

50 years ago Jane Jacobs, in her book The Death and Life of Great American Cities4, identified a series of principles that support a dense and vital city. The same principles remain valid until now, namely supporting the density of the built environment through diversity, of constructions as well as of activities, through multiple functions, small building components forming larger units, a mix of buildings of different conditions and a high concentration of population, all for the purpose of supporting diverse actions and interactions. Density of the built environment itself cannot generate quality and direct benefits by exclusively applying principles of quantity, for density must be related to other factors such as building shape, mixed use or organisation of activities, in order to generate environments of rich activities. The principle of sustainability is also important in relation to the qualitative aspect of future developments. Architectures must relate in a sensitive manner to the existing urban character, to incorporate local influences while promoting diversity and being adapted to climatic, cultural and social local character.

The key to sustainable future high density architectures lies in generating built environments capable of adapting to changes. These models will be flexible, renewable, adaptable and capable of transformation and self-redefinition in relation to context changes. The adaptability of the built environment in a future scenario can result either from the compositional pattern of designing the whole, either through over-engineering and bio-mechanization of building materials and technologies. I am interested in the first approach, that of context adaptation through the composition of the whole made out of small-scale units, various and vaguely defined, basically a large-scale object constructed ​​of many small sub-units. The granulation of the whole is what generates spatial quality as well as quality of use, enabling the adaptation to context. A possible future scenario includes large-scale spatial organizations made up of multiple parts that can interact in complex ways and generate simultaneous responses to the challenges of context. Their adaptation can be achieved either by changing the inhabitants and the use, either by physical regeneration done by removing or grafting new subunits according to needs.

Monolithic spatial growth / fine-grained spatial growth

Img 1 – Monolithic spatial growth / fine-grained spatial growth

From a functional perspective, projects being build, managed and adapted incrementally can accommodate a wide range of functions and users. In relation to function, it is important to avoid both formal and functional over-determination in the design process, the primary objective being that of generating various support spaces with vague definition that can accommodate manifestations and activities as varied as possible. Those spaces are capable of physical and moral sustainability in the long term, compared to rigidly modeled spaces correlated with a unique function, whose chance of survival is small if the function vanishes. The solution is to produce spatial ambiguous models, whose ambiguities can support functional changes or ongoing uses and may lead to changes in the urban tissue in relation to changes in context. Viability of an architectural model is ultimately verified by its user’s satisfaction and the built environment must be able to negotiate almost in real-time with the needs of each actor involved in urban life.

Decomposition of a solid into micro-units / model of adaptive growth consisting of micro-units

Img 2 – Decomposition of a solid into micro-units / model of adaptive growth consisting of micro-units

Adaptable spatial growths, fine-grained and composed of agglutinated micro-units already exist as architectures of the limit, of vernacular architecture, in slums and in the areas illegally occupied by the poor communities. Spontaneous architecture is an incremental process, and its developments are able to constantly adjust to the situation of the physical and social immediate context, being more adaptable to changes and thus more resistant. To imprint these qualities to a large scale high density architecture can generate an architecture that’s sustainable and responsive towards its context, and the product acquires regenerative qualities. There are a series of contemporary projects of exploratory type in this regard, much of them being generated by architectural competitions. Projects using principles of spontaneous growth have emerged in studies, exploratory researches or competition projects, suggesting possible models of adaptive architectures. One such project is Scrap Skyscraper belonging to the group Projeto Colectivo, which uses a fix vertical circulation core and a solid base for generating a housing complex with augmentative growth, consisting of residential units that add up over time, with an additional exoskeleton-like supporting structure that enhances and extends in relation to the growth of the built body. The master thesis project Favela Cloud developed by Johan Kure, Kemo Usto and Thiru Manickam proposes a fluid incremental growth model composed of micro-units with different functions consisting of a mix of housing and cultural functions, related to knowledge and learning processes. The composition of units is the result of a computational process that follows the growth principles of the favelas and the generation of a compact “cloud” hovering above ground, placed on stilts.  Similar principles have begun to migrate towards constructed projects such as 56 Leonard Street by Herzog & de Meuron, a residential skyscraper  in New York, which proposes a series of 145 residential units with unique character, although diversity here appears to be more a commercial asset.

An important challenge in generating adaptable architectures is related to the design process, which involves the integration of diversity as a constructive force, as opposed to the multiplicative process so far. Either it is sought to design a generic framework that functions as skeleton, onto which basic modules are inserted, while other modules will appear or disappear over time, driven by the change context, either a finite object resulted by running all possible future scenarios. The process of growth and adaptation in the first case is not necessarily programmed by design, the original framework acting as a directing skeleton onto which growth can occur spontaneously.

One of the main challenges of the future is adaptation – to the decrease of resources, to the sociopolitical and economical context, to climate changes. Architecture will have to find its own way to adapt.

  1. Patrick Schumacher, My kind of town, http://www.architecturetoday.co.uk/?p=22997, accesed in 10.09.2012
  2. Nic Clear, A Near Future, in: Castle, H., Clear, N. (eds.), “The Near Futures”, Architectural Design Vol. 79, No. 5, September/October, Wiley, London, 2009, p. 6-11
  3. Chye Kiang Heng, Lai Choo Malone-Lee, Density and Urban Sustainability: An Exploration of Critical Issues, in: Designing High-Density Cities for Social and Environmental Sustainability, Edward Ng (ed.), Earthscan, London, 2010, p. 41-52
  4. Jane Jacobs, The Death and Life of Great American Cities, Random House Inc, New York, 1961

The need for housing is a basic need, which in its elementary form is translated as need for spatial support and shelter, being a direct follow up of the population growth and of people’s migration towards large cities. Globalization, urbanization and other sociopolitical factors have also heightened the dynamic of the relationship between cities and their surrounding outer urban areas. In relation to rapid urbanization, more people are attracted to cities in a dynamic shift from rural to urban. Most of them leave behind an agricultural life just to start from scratch in an environment they are unfamiliar with. Employment is one of the major factors in determining migration.


All large developing cities attract slums, as a natural and necessary part of the urbanization process. By attracting cheap labor that exceeds the possibility of the city to ensure housing in accordance to the needs of the newly arrived, overpopulation in poor peripheral areas is created. Most of the people that come to large cities in search for work are poor and cannot afford to pay rent. Therefore, living in slums becomes the norm for many, simply out of necessity and not by choice. According to current numbers, one in seven people live in squatter communities – illegally grouped communities or neighborhoods on terrains on which they lack ownership. The act of squatting can be either linked to poverty and to basic deprivation, being also described as “third world squatting”, or can be based on political grounds. Squatting due to poverty derives out of a conflict between power, property and urban development that creates the need for housing but fails to provide a solution. As a result, people are trying to solve the housing problem on their own, generating social and legal conflicts.

The definition of slums is complex, depending on a group of factors that point out the basic deprivations in the living conditions in poor neighborhoods, according to UN-Habitat, the United Nations Human Settlements Programme. The main deprivations are: the nature of housing, not being permanent and durable, sufficient living space, easy access to safe water, access to adequate sanitation and the security of property. These deprivations are not homogeneous for all slums and do not necessarily manifest themselves simultaneously [1]. Overall, one in five slum dwellers suffers from at least three basic deprivations and is living in extreme poverty. Slums can also generally be defined as invasions of public or private land with self-build shelters developed by poor groups; the groups of dwellings lack infrastructure and planning. Those communities lack ownership in a legal sense, lack government and city services. Living conditions in all slums are very low, and basic urban services like water, sewers or electricity are missing. The main reason they exist and function is that they offer cheap housing and also ways to earn a minimal living, while the cost of housing here is much lower than in legal urban areas.


The architecture of the slums is determined by local conditions and local materials, and can be therefore defined as vernacular architecture. Slum architecture itself doesn’t follow any trend or architecture style and is solely the outcome of direct sheltering necessities. Still, this architecture manages to bear similar characteristics all over the world, being done in a similar fashion and having an easily recognizable image for everybody [2]. The pattern of land occupation, the size of the outer volume and the interior dimensions of a living cubicle are all derived from minimal living necessities. All those characteristics, as well as the similar general image of slum buildings lead the architecture of urban slums to become a global phenomenon, with slight regional differences given by site conditions. The main reason why an architectural phenomenon outside the boundaries of legitimate architecture manages to generate a global current is found in the constant similarity of the contexts of implementation – slums are almost organic growths generated in urban environments, inside urban landscapes, and have similar composition principles. The overall way of construction and composition is not planned, being random and lacking hierarchy. The relation between parts is chaotic, but the assembly take a precise account on all the characteristics of the natural or artificial terrain, onto which it moulds onto, as in the slums of Rio de Janeiro or Sao Paulo in Brazil.

Figure 1. Comparative study of occupation patterns and urban grain.Some common features of slum housing recognizable everywhere include: similar building indexes and similar densities; the minimal character of the volume, being a minor architecture build according to possibilities; similar sizing of the interior space generally defined as a unique multifunctional and fickle space in which the life of a whole family evolves; making use of simple volumes and construction techniques; very short construction time, compared to the period that other urban structures need to grow and develop, partially due to the simple building method that doesn’t require long building processes and also due to the lack of planning phases prior to the beginning of the construction; the constant need of improvement and renewal due to the temporary character of the constructions.

Figure 1. Comparative study of occupation patterns and urban grain.

The houses build by the poor are the direct outcome of the opportunities, building skills and knowledge of the owners in relation to the location, to resources and to the economic status, houses being build by their owners alone or in cooperation with their neighbors. The former dwellers of the rural areas have enough vernacular construction knowledge due to the specific activities sustained in the rural environment, where they usually built their homes by themselves or benefited of the support of the community and where grew their own food. The materials used for buildings are generally scrap materials, recycled or recuperated materials, which directly influence the quality of housing. Those dwellings are actually shelters, constructions of temporary character that need constant maintenance, refurbishment and re-construction. They generally offer a simple protective shell, which in most cases doesn’t even guarantee the most basic protection for their inhabitants. Bad housing conditions are the main cause for physical illnesses, due to the absence of minimal sanitation and poorly insulated construction elements, but they also draw other more subtle dangers, such as the lack of education due to lack of electricity, lack of security due to lack of construction sturdiness, but also risks of fire and burglary. This is also the main reason why slum communities are the most endangered group in case of natural disasters. It becomes obvious that a bad housing quality directly affects a large number of people, and therefore perpetuates poverty. Still, sturdier constructions are only generated where the local government policies accept the slums and do not fight to eradicate them [3]. Otherwise, it makes no sense to invest labour and money into a building that might be demolished anytime in the near future, and therefore the slum remains primitive in its composition.


Although slums are located right on the edge highly developed urban areas, their inhabitants often remain inside the limit of the slums and are only active within them, remaining apparently unseen for the rest of the city. Major slums are partially or totally self-governed by persons within the group and develop specific economies in the form of light industries, commerce and services. All those activities manage to produce enough money for the inhabitants in order to ensure them a life from day to day. Beyond the direct benefit brought to their dwellers, subterranean economies directly help the economy of the broader urban body of which they belong. In relation to the developed city, the prices of products resulted from slum production are highly profitable, and the market of the slum is a fertile trade ground. In slums, street vendors and various non-licensed operators managed to generate sufficient jobs for all residents out of sheer necessity of survival. Those small enterprises have proved to be competitive in the global market economy. On the other hand, many major corporations have admitted the possibility to explore the power of unlicensed entrepreneurship, such as the case of the mobile telephone industry that uses the slum retail market [3]. Informal economy is characterized by a larger dynamic compared to its legal forms, strengthened by a great sustainability of specializations. Another feature that helps to the success of these businesses is the fact that they take place in urban areas, and due to the high density of slums, business activities cover a small area of land in relation to the city, so that there is no need for transport services towards users. It is much cheaper and easier to provide services and products in a small area, offering a service from a fixed location, or providing services that require minimal travel by primitive transportation means that do not consume fuels that might lead to increased costs. Still, the paradox of this functional informal economy is that the poor earn exactly enough money to survive, but never enough to advance up the social leather.


Throughout history, most of the major cities have been built using poor populations that contributed in the construction itself and in strengthening the economy of the central urban core. In contemporary culture, poor satellite towns and slums were considered sources of conflict and negative areas compared to cities in development, but now their importance in the overall process of urban growth is being reviewed. Many contemporary viewpoints consider the slums as a resource for the global future, by the force embedded in this dense structure of people, activities and relationships. The specific force of slums is based on the dense environment, on the social relations and the resilience of their inhabitants, strengthened by the age of the population, which is generally young. The entrepreneurial spirit of the inhabitants keeps the community alive through the economy and the constant housing rebuilding, while the social ties within the slums are very tight, based on relationships of caring, arising from the condition of poverty. Slums contain qualities often invoked by architects and urban planners as attracting the quality of an urban space: they are easy to navigate on foot, containing mixed functions obtained both by the practiced trade and through the multiple uses of housing, and have high density [4], while they are in a continuous process of rewriting and transforming.

One of the most appreciated qualities of slums in this moment is their extremely low energy footprint and their ecological quality, despite low sanitary conditions. Although it seems rather hypocritical to appreciate a quality resulting partly from extreme poverty and partly due to the closed manner in which these communities work, in a world concerned with minimizing the energy footprint per capita it is essentially to study the patterns that regulate this mechanism. The compactness of housing units in the settlement makes the slum itself an ecological model of maximum energy efficiency. Another environmental quality of these communities is their extreme inclination towards recycling, which in most slums represents a way of life. All materials that can be used for constructions are collected and recycled, and the job of collecting garbage for recycling purposes is an occupation that ensures survival. Perhaps the greatest virtue of slums lies right within the qualities of the people that make up the community. Most people are originating from rural areas where they grew their own food and built their own homes, so their knowledge in these areas is vital for surviving in minimum conditions. In addition, the resilience of people from rural areas to harsh conditions is increased and exercised, compared to people raised in urban areas, less trained in the sense of surviving in minimum conditions and with limited resources available. Among the specific spatial qualities that stand out are the opened private spaces, especially in warm climate environments, and the strong relationship with the exterior, their openness towards the public space and neighborhood. Each one sees and is seen constantly, and this fact leads to strengthen the communitarian spirit and lowers crime rates. Slums manage to generate a continuous space of activities and social communication.


For the future development of cities and especially that of architecture, understanding the mechanisms that lead to the functioning of slums is essential. Therefore, the architecture of slums can serve as a model for improving the living conditions in slums, as well as for the future design of sustainable high density residential environments. Concerning the way of operating with these urban growths, it is clear from past experience that denying or destroying them without following any coherent politics of compensation will not bring any positive outcome. Leading an official punitive policy by using force, unrelated to the reality of life in slums, is wrong. Collaboration between government, local municipality and slum communities is necessary. Those communities contain within them a huge social and economic power, managing to survive and resist to all forced attempts to remove them.  A possible solution in managing these growths is to regulate them partially, in a fragmentary and elastic manner, providing legal support and a minimal utility network that would work like a vague framework. The main principles to be followed are retrieving principles of composition from existing built structures of slums and the direct involvement of the community in the construction process. The community is in fact the main actor in shaping and determining the built environment [5].

Minor architecture, of marginal areas and slums, represents s process of densification from within, made out of growths done by additive transformations, sensitive to context and to vicinities. Spontaneous architecture is an incremental process, and those developments are capable of constant adjustment to the physical and social immediate context, being much more adaptable to changes and therefore more resistant. Spontaneous growths, through the lack of regulation and design, include a greater capability for adapting. They are flexible and vibrant urban structures, which can be sustainable physically and socially in the long term. The principles that can be extracted from the architecture of slums can theoretically generate sustainability for any pattern of high density architecture.

One of the main challenges of the future is adaptation – to decreasing resources, to the socio-political and economical context, to climate changes. In this regard, correct future planning involves generating a complex agglomeration of multiple organisms, whose parts interact in rich and complex ways, in order to meet in synergy the city functions.


[1] UN-HABITAT, United Nations Human Settlements Programme,http://www.unhabitat.org/documents/media_centre/sowcr2006/SOWCR%205.pdf

[2] García, Tere,The Vernacular Architecture of Swelling Cities, February 8, 2011, 12:41 pm, http://archithoughts.wordpress.com/2011/02/08/the-vernacular-architecture-of-swelling-cities/, accessed in 5.07.2012.

[3] Neuwirth, Robert, Global Bazaar, Shantytowns, favelas and jhopadpattis turn out to be places of surprising innovation, Scientific American, Volume 305; 2011, pp. 56-63.

[4] Tuhus-Dubrow, Rebecca,  Learning from slums, March 1, 2009, http://www.boston.com/bostonglobe/ideas/articles/2009/03/01/learning_from_slums/?page=full, accessed in 20.07.2012.

[5] Quick Guides for Policymakers no. 1 – Urbanization, Housing the Poor in Asian Cities, United Nations Economic and Social Commission for Asia and the Pacific, Bangkok, 2008.


photo by: http://www.photomichaelwolf.com/hongkongarchitecture/unten.html

The continuous growth of the human population is stressing out profoundly the global resources, out of which one is physical space. It is expected that in the near future the population and especially the number of people living in the cities will continue to rise. The population growth must be provided with physical and spatial support in the form of dense urban environments and architecture with similar qualities. Under those conditions, high density architectural forms represent the most viable models for the future in general and for living environments in particular.

The architectural object is a spatial system that offers support for a complex network of social relations that facilitate mutual proximity. Understanding the models of high density architecture can offer a key to successful and healthy architectural design. The main concern should focus on identifying best models for future living environments, and how they can offer a correct support for residents in relation to the crowding degree.

I would first focus on studying social implications of high density environments, followed by a definition of the concept of density in relation to the build environment, and further on an overview of the relations between highly populated environments and the forms of dense architecture, following especially positive models of design.