In relation to dense residential environments, I am also interested in the study of collective housing typologies.

Collective or mass housing is defined primarily by quantity and it acquires its spatial quality through grouping. This type of dwelling houses large numbers of people with varying degrees of housing quality. Within it the housing units are closely grouped, according to rules of horizontal or vertical assemblage, generating spaces with public, semi-public or private character in which certain social practices of housing unfold. Collective housing draws its name origin from the way in which the building is accessed, namely by a common path serving all the units [1].
In an attempted typological classification of contemporary collective housing models of high-density, I turned towards a non-exhaustive generic formal classification, based on the studies of Mozas J and Per AF from the “Density Series” books [2]. Each of the typologies uses as starting point the individual housing unit, the apartment, which is consequently multiplied in an identical or variable pattern of configuration. The typological categories vary according to composition principles based on the housing unit, on size and by the way in which the building relates to the urban tissue.


Starting from the singular and abstract typological unit represented by the individual house, the first category is driven by multiplying, joining or overlapping multiple units. The configurations generated by those operations are either classical attached or row houses, either contemporary types of folded row or stacked houses.
The individual unit is usually related to the terrain, benefiting of a court or a terrace and of direct individual or paired access from the ground level. This category makes the transition from individual housing to collective housing of a higher degree of density.



The second typology represents a quantitative increase in size, in number of individual units and scale compared to the “house” typology. The block height is moderate, usually ranging between 3 and 5 levels; this height is traditionally justified by the number of levels convenient for walking. Its relative low configuration, its flexible footprint on the ground and its scale allow the object to enroll organically within the context.
The block can be freestanding on the plot, it can have free sides or it can continue an existing building by cleaving onto a party wall.


City Blocks

The city block  is an urban building flanked on all sides by streets in relation to the urban fabric. Its scale is directly related to the scale of the city. The city block generally involves a large spatial diversity and a relatively high privacy degree. It can have the same height as the block typology or higher, depending on the context. Buildings ranging between 4 to 7 levels are ideal in terms of energy footprint, which is lower than that of taller buildings.


High-Rise Buildings

The high-rise type, also known as tower block, is represented by tall buildings with multiple levels. There is no universal definition for the number of levels that determines a building to gain this status; this height is variable according to different geographic areas.
This typology is justified by economic considerations, not only in relation to construction costs, but also in relation to urban infrastructure and land resources. Their impact on the neighboring urban tissue is high and the main disadvantages are excessive shading and energy consumption.
The stacked units block is the most interesting type from my point of view, being able to generate spatial quality and diversity. It derives from additive processes of small scale units or overlapped uneven floors.


Mixed Solutions

The mixed solution typology involves combinations of the above, justified by context and project brief. There are no precise formal categories for this typology.


[1]   Zahariade AM. Arhitectură Locuire Oraș, ALO 2009-10. Second year’s course, second semester. Department of Hystory & Theory of Architecture, Faculty of Architecture, UAUIM, Bucharest.

[2]   Mozas J, Per AF. Density: New Collective Housing. A+t ediciones, Vitoria-Gasteiz; pp. 14-17, 2004.


Population density is a phenomenon related to the way in which the population is distributed on the land surface. The population is unevenly distributed across the land, reaching high concentrations in large urban areas while large areas of land remain uninhabited, because people naturally tend to concentrate in areas with desirable conditions, like those of urban areas. The differences in population distribution are high both across countries and between regions of the same country [1], and thus the concept of density of the built environment has relative connotations when trying to compare indices of different areas.

Starting from this fact, it becomes clear that the exact definition of the term high-density architecture can be difficult. The term “density” is itself a complex concept, involving some diversity in terms, and defining it is important before beginning a discussion on density in relation to architecture.

The Definition of Density

High density refers either to physical density, namely the density of a large number of people or the built density related to the land surface, either to subjectively perceived density in relation to the environment and to other participants into a certain space. Physical density is a numeric measure of the concentration of individuals or of physical structures in a certain geographic unit, being a spatial objective indicator, quantitative and neutral. In practice, it only makes sense when linked with a specific reference scale. On the other hand, perceived density represents the individual perception of an estimated number of people present in a given area, of the vacant space and its organization. The character of space itself is important for the perception of density, but the interaction between individuals and environment as a whole is more important. Also the individual cognitive attributes and socio-cultural norms are factors that contribute to this interaction. Perceived density doesn’t only refer to the relative relations between individual and space, but also to the relations between individuals located in the same space.

The definition of density in relation to built environment can have different meanings or different quantification according to the method of analysis and spatial indices taken into account. There is no universal standard formula, only some of the formulas are being used more as opposed to others. Usually, in architecture and town planning, two categories of measurement are used for physical density: population density (Fig. 1) and building density (Fig. 2). Population density is defined as the number of individuals or households per given area, and the building density is defined as the ratio of building structures related to plot surface. All those measures are used in urban planning policies.

population density
Figure 1. Population density

built density
Figure 2. Building density

Building density has a complex relation to urban morphology, playing an important role in determining the urban form. Different combinations between the plot ratio and site coverage will manifest into a variety of different built forms, and urban development of the same density can take very different urban forms [2].

The differences between the surface distribution of population density and that of building density are visible when comparing data of almost every urban tissue. The following example illustrates the difference between the two densities in the case of Timișoara, by graphically expressing the data for the year 2011.

Z:1_PROIECTE63_pug4_work1_urbanism1_ETAPA ANALIZA2_PRED

Figure 3. The difference between the distribution of densities of people and buildings in Timișoara.

Source: illustration from the board Development Analysis I 13_Densities, General Urban Plan (PUG) of Timișoara, drawn by Vitamin Architects based on data provided by the City Hall of Timișoara and used with the consent of Vitamin Architects [3].

In reality, especially when the geographic reference unit is one at large scale, the distribution pattern of people or buildings can vary significantly. To solve the spatial variation of density, different measures have been introduced, such as density gradient or density profile. The density gradient is a composite measure of density and is defined as the rate in which density decreases in relation to the distance towards a reference location, usually calculated according to concentric circles (Fig. 4). By comparing the patterns of density over a period of time, the process of spatial evolution of the city can be depicted, showing either decentralization with a drop of population density in the center and increased density towards the outskirts, either centralization with a growth in population density in both center and outskirts, and the expansion of the borders (Fig. 5) [2].

gradient densitate ENG

Figure 4. Population density gradient for an abstract case.
Figure 5. Density gradients over time: (a) progressive decentralization; (b) centralization.
Source: Illustrations adapted and redrawn after Vicky Cheng (2009, p. 8).

From the perspective of rapid urbanization, the relationship between urban density and built form has always been an important focus of research, determining massive mathematical and geometrical investigation upon the spatial benefits of buildings with multiple levels. The presented definitions and measurements of density are the most relevant ones in relation with the subject of density from an architectural point of view, but they are not the only ones.


[1]   Freedman, JL. Crowding and Behavior. San Francisco: W. H. Freeman and Company, 1975.

[2]   Cheng V. Understanding Density and High Density. In: Ng, Edward (Ed.). Designing High-Density Cities For Social & Environmental Sustainability. London: Routledge; pp. 3-17, 2009.

[3]   Public document downloaded from the City Hall of Timisoara web-site:

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,

[2] García, Tere,The Vernacular Architecture of Swelling Cities, February 8, 2011, 12:41 pm,, 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,, 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.