Natural Building Materials and Social Representations in Informal Settlements: How Perceptions of Bamboo Interfere with Sustainable, Affordable, and Quality Housing

Abstract

Building with natural materials has proven to be a sustainable approach in addressing the needs of affordable and healthy housing and improving living conditions in informal settlements in an era of ecological transition. In view of this, the use of bamboo as a building material is considered a promising practice. However, although many traditional building techniques incorporate the use of bamboo, its application in contemporary informal settlements is disputed. This interdisciplinary study critically explores the social and cultural factors limiting the use of bamboo in a contemporary context by investigating housing perceptions and practices in an informal settlement in Colombia. Results show how the combined effect of cultural globalization, modernization, and the standardization of construction practices have marginalized and are now devaluing traditional knowledge on natural local building materials. Structured observations and in-depth interviews reveal that inhabitants’ refusal of the local bamboo building tradition, their representation of bamboo as an unsafe and temporary material, and their choices of less sustainable contemporary building materials, are better understood by situating these preferences within the complex system of the community’s imaginary. These social representations validate housing behaviors for their symbolic implications rather than for their actual consequences on livability, comfort, and overall dwelling quality. The study also discusses the limits of policies promoting natural building materials in housing when exclusively focusing on technical performance, while neglecting the prevailing impact of the cultural domain on housing preferences and behaviors.

1. Introduction

The exigencies of the climate crisis in its various manifestations and the pace of rapid urbanization globally act as clarion calls for design disciplines to respond creatively in the search for sustainable solutions. Confronting resource scarcity and climate change, planners and designers must rethink their practices in the transition to more sustainable models of intervention. A promising approach to such ends in the broad field of sustainability studies is the development of evidence-based strategies for increasing local resilience, namely ‘adaptation’ [1,2]. What makes this approach particularly interesting is its focus on solutions tailored to local and regional specificities.

Traditional knowledge is defined as “practical and normative knowledge concerning the ecological, socio-economic and cultural environment, inherently systemic […] and experimental […], originated by people and transmitted to people by recognizable and experienced actors” [3]. Traditional knowledge can be a useful resource to implement locally-led approaches, as it is usually based on a balanced and measured use of accessible local natural resources. One key concept that combines local traditional knowledge with sustainable design is ‘retro-innovation’, the critical and integrated approach adopted in agriculture and in rural communities to address contemporary issues through received cultural practices [4,5]. The introduction of retro-innovation into contemporary architectural methods implies drawing on vernacular building traditions, namely that body of locally based know-how and practices not affected by industrialization or specialization which a community passes on from generation to generation [6,7]. The product of generational and even centuries-old processes, vernacular building cultures use natural and local materials in their infrastructural adjustment to evolving needs and capacities and to the transformations of their surrounding context, including catastrophic events. Each vernacular building culture, even in regions with extreme climates, offers a veritable encyclopedia of locally based, structurally reliable, economic, and efficient building solutions with low environmental impacts. Therefore, vernacular building cultures have already responded to a host of issues being faced by contemporary architecture [8,9,10,11].

The international community has already begun to acknowledge the positive effects engendered by the recovery of traditional vernacular building cultures for their contribution to the sustainable use of resources, spatial justice, safe and affordable housing, and reduction of environmental building impacts (SDG.11, Agenda 2030, UN). Retro-innovation can be a means to combat housing precarity and development of urban informality in the Global South. Specific efforts in this regard are already underway by the UN, international NGOs, and other civil society actors. However, the strategies to reintroduce traditional building cultures in informal contexts frequently adopt prescriptive [12] and technocentric approaches which largely focus on technical dimensions while neglecting the social and cultural domains [13,14]. These approaches ignore the underlying tensions which can lead to a community’s refusal or limited acceptance of traditional techniques and natural materials. In addition, co-opting and disseminating traditional building cultures narrowly and divorced from a social context represents an uncritical application which does not result in the actualization of retro-innovation’s full potential [10].

The Colombian case study presented here illustrates how the sociological analysis of the dwellings and dwellers can help to understand the issues related to the use of traditional building knowledge and bamboo as a sustainable building material. Bamboo is a strategic resource in Colombia, already part of a well-established building tradition and now the subject of research and policies to improve sustainable housing. However, as this interdisciplinary study shows, bamboo, natural materials, and traditional knowledge are associated by inhabitants with a number of negative meanings and perceptions which limit their use to very specific contexts and situations. This research offers insight into the importance of investigating such meanings and perceptions to design successful retro-innovative interventions, especially those involving natural building materials.

2. Research Background

2.1. Housing Issues in Informal Settlements

The global growth of urban informality has transformed urban systems to the point where it can be considered one of the principal modes of contemporary urbanization [12,15,16,17,18,19]. ‘Informal settlements’, the characteristic exemplification of urban informality, are squatter neighborhoods or districts built outside the confines, regulations, and zoning practices of state norms, integrated in varying ways to the latter’s normative economic and spatial contexts, but nonetheless resisting state control and schematization in the official topography [20,21]. According to UN-Habitat data, in 2018 there were slightly more than a billion people living in informal settlements worldwide, meaning that almost 1/8th of the global population lives in an informal settlement. The percentage of those living in informal settlements declined between 1990 (43.3%) and 2014 (23%), yet has remained stable since. About half of the informal settlements’ inhabitants live in Asia (589 million), a fourth in Africa (228 million), and around a tenth in Central and Latin America (110 million). In Colombia, more than a quarter of its fifty million inhabitants live in informal settlements (28.5%) [22].

Informal settlements are typically formed by migration flows and evictions which other modes of urbanization cannot regulate, and are prone to collective forms of self-organization which organize services typically managed by municipal administrations. Informal urbanization can thus be seen from different perspectives, interpreted either as a reflection of state abandonment and lower standards of living, or as an opportunity in the development of autonomous participatory urban communitas. Informal settlements within cities pose structural problems through their serious deficiencies in terms of housing safety, hygiene, comfort, and minimum size standards [23]. They usually arise in environmentally-compromised residual areas, lack permanent structures which comply with building or planning regulations, and basic services, and the quality of their infrastructure and buildings depends on the limited resources of the occupants [17,20,24].

Despite these issues, urban informality, both in terms of its spatial and economic components, has been seen as a compelling alternative to dominant formal modes of urban organization. Several scholars consider urban informality as an ideal space for the emergence of collective dynamics and new forms of social cohesion, allowing an emancipation from the control of the formal urban layout, whose rigidity is incapable of accommodating transformations and social energies [25,26,27,28,29,30]. According to these scholars, informality allows the creation of a shared communal identity through the spontaneous dynamics of individual interactions and collective empowerment from organizing and mutual aid.

Institutional attitudes toward urban informality are notably ambivalent when aiming for the gradual inclusion of buildings or inhabitants into the formal fabric of the city through settlement upgrading and land titling. Informality remains a sensitive and contentious topic: it raises issues on the ‘right to the city’ while questioning the ownership property model and dominant economic interests. Because of the socio-economic complexity of the phenomenon, policy responses to informality, such as upgrading and land titling, are usually only compensatory in nature instead of transformative [12,31,32]. Modifying sub-par housing conditions or relocating settlement dwellers into new accommodations is clearly easier than devising new truly reform-oriented housing policies that provide for the redistribution of resources and power within the urban system. To some extent, the emphasis on mitigation and adaptation results only in the deferral by public actors of solutions for urban informality.

The strategy of in-situ upgrading seeks more acceptable and livable informal settlements through architectural upgrading, structural consolidation, partial or total reconstruction, service provision and eventually land titling [31]. These methods are frequently geared towards self-help and technical empowerment of informal dwellers and are financed or co-financed by non-governmental organizations and economic aid institutions. In this scenario, retro-innovation is increasingly seen as a relevant approach to guide and inform upgrading strategies. Utilizing a given community’s knowledge of traditional techniques and taking advantage of its cost-effectiveness is particularly helpful in addressing the hygienic, structural, and architectural deficits of informal settlements.

However, most research on the upgrading of informal settlements focuses solely on structural and technical objectives, such as building renovation, structural reinforcement, technical requalification, and the development of reproducible and adaptable construction techniques. Little to no consideration is given to the opinions and perceptions of settlement inhabitants, either before or after the interventions. Yet, without the feedback and participation of residents, the outcomes of interventions cannot be truly evaluated and properly measured. The adoption of sociological tools for understanding inhabitants’ perceptions and social context can instead help predict the outcomes of interventions on informal settlements. This approach stems from an acknowledgment of the agency of informal dwellers in the creation of their spatial and social environment—the fulcrum in a positive reading of urban informality. More than merely recipients, informal dwellers are the creators of informal contexts and, by producing the social representations that orient their behaviors and choices, they play a central role in the redevelopment of their community [33]. Knowledge of inhabitants’ beliefs and preferences is crucial for forging housing interventions that are long-lasting and responsive. Otherwise, the introduction of any innovative or retro-innovative technique in housing upgrading may very well face social or cultural backlash and hesitancy. Therefore, knowing the cultural associations a given community holds towards different types of dwellings, buildings, and materials facilitates the adoption of solutions that are little considered or not already familiar to the community.

2.2. Bamboo Housing and the Ecological Transition in Architecture

The use and implementation of bamboo is strategically important in the ecological transition of building practices, and can be successfully utilized in settlement upgrading and urban housing interventions.

As a building material, bamboo is very sustainable: resistant, widely available, inexpensive, easily workable [34]. Unlike most common modern building materials, bamboo’s carbon footprint is negative [35,36] and its production is environmentally friendly, as bamboo cultivation is a form of land preservation [37,38,39]. By virtue of its botanical composition, bamboo is inherently both rigid and light [37,40]. Untreated bamboo suffers from direct exposure to sun, rain, and humidity, but properly collected and treated bamboo is resistant to fungi, water, and fire, and some bamboo species, such as Guadua angustifolia Kunth, have excellent mechanical and anti-seismic properties [41,42]. Due to these qualities, bamboo can be used to create resistant, comfortable, and healthy buildings, providing ventilated, unpolluted, and cool indoor environments [37,43]. A bamboo building properly made is reliable, easy to maintain and dispose of, and has a life expectancy of several decades—comparable to that of other building materials [37,38,42].

Bamboo housing is widely utilized worldwide, especially in tropical and subtropical regions, and it is estimated that over one billion people live in houses that employ bamboo as the main building material [39]. Several vernacular building traditions center on the use of bamboo, providing a vast technical knowledge about, among others, bamboo treatment and installation phases, which are central to bamboo buildings’ overall quality [37,40,42,43,44,45,46,47]. The vast majority of current building techniques to maximize bamboo’s qualities derive precisely from traditional building cultures [38,42,48].

The robust traditional and empirically based knowledge of bamboo construction and its countless demonstrations of resistance to weather, time, and catastrophic events has animated research on bamboo housing. Nevertheless, most scientific research is focused on exploiting bamboo’s mechanical properties in creating engineered, hi-tech, and prefabricated building techniques—such as bamboo panels, laminated bamboo, and other industrial bamboo-based products, e.g., [36,49,50]—while little research looks into the recovering and enhancing of traditional knowledge. This approach is consistent with the needs of modern large-scale commercial construction, which is engineered and standardized, and demands uniformity and predictability from its structural material [35]. Structural engineering, which produces current building codes and standards, took a long time to accept bamboo into the range of normed building materials [51]. The international standard for measuring and determining bamboo’s physical and mechanical properties was implemented only in the early 2000s, by the International Organization for Standardization (ISO), supported by the International Network for Bamboo and Rattan (INBAR). What hindered the validation of bamboo is its inherent heterogeneity [35]. The strength characteristics of bamboo depend on its anisotropic structure (i.e., the fact that its response to load stress is different if measured on different axes of the material), and external conditions, such as humidity, can slightly alter its behavior, although not affecting its resistance.

Despite being included in building codes, bamboo is still considered a secondary building material. Its inherent heterogeneity and the need for preventive treatments conflict with contemporary engineered and standardized building practices. Moreover, even if bamboo, as a building material, has been tested and included in international codes, traditional bamboo building techniques are still missing from most anti-seismic building codes. Even when included, as in the Colombian case (as discussed in the next section), traditional bamboo techniques are hybridized with modern and engineered materials.

2.3. Bamboo Housing Revival in Colombia

Countries with a greater availability of bamboo, such as Colombia, Ecuador, and India, have pioneered bamboo building codes. In 2002, with the Legislative Decree 52, Colombia was possibly the first country to include a traditional bamboo-based building technique, namely Bahareque, in its national anti-seismic building code (NSR-98, [52]). The current version of the Colombian Building Code [53] is among the most comprehensive in the world in its application of bamboo [51]. It is not surprising that Colombia anticipated the codification of bamboo regulation, given its important tradition of bamboo housing. In fact, Guadua angustifolia Kunth, one of the most robust species of bamboo, is native to the Andean region of Central Colombia. The country’s traditional bamboo building technique, Bahareque, originates from the Paisaje Cultural Cafetero, which was declared a UNESCO World Heritage site in 2011. According to the UN Food and Agriculture Organization (FAO), Bahareque is one of the three main bamboo housing types, together with ‘traditional’ (bamboo culms-involving dry techniques) and ‘modern’ (laminated and prefabricated bamboo-based architecture) [39]. A typical Bahareque wall consists of a bamboo (and/or wood) frame and a sheath of split bamboo mats, namely ‘esterillas’, or wood strips, filled with earth or clay and covered with lime (Bahareque de Tierra), wood panels (Bahareque de Tabla), metal sheets (Bahareque Metalico) or steel mesh and cement mortar (Bahareque Encementado) [54]. Developed in a tropical region with high seismicity, Bahareque stands out for its earthquake resistance [42,54,55,56,57,58,59].

The inclusion of Bahareque in the 2002 code came about after the 1999 Quindío earthquake, where Bahareque buildings showed outstanding anti-seismic performances. Colombia is a highly seismic area: according to U. S. Geological Survey data, there has been nearly one earthquake per year of a magnitude greater than 6 in the country’s Andean region alone since 1999. In particular, the 1999 Quindío earthquake was the country’s most devastating of the 20th century. With a magnitude of 6.2 and an intensity X in the Modified Mercalli Scale, that earthquake caused approximately 1200 deaths, destroyed 50,000 buildings and displaced more than 200,000 people. According to the Reconnaissance Report prepared in 1999 by the Multidisciplinary Center for Earthquake Engineering Research of the University at Buffalo, State University of NY, the Bahareque houses in the Armenia area withstood the earthquake well, along with rare cases of masonry buildings constructed according to the modern anti-seismic standards, and most of them did not suffer any damage (pp. 11–18, [60]). The gravity of this earthquake and the performance delivered by bamboo buildings well demonstrate the potential of bamboo housing in seismic areas [55].

As seen above, Bahareque exists in different versions depending on the sheathing material. However, the only version mentioned in the anti-seismic national code is the contemporary version of Bahareque Encementado, the hybrid technique combining a bamboo frame with cement and steel mesh. Colombian government campaigns for the recovery of Bahareque in the Paisaje Cultural Cafetero only refer to Bahareque Encementado, and this is the only version taught in the public training programs for builders at the National Training Service (Servicio Nacional de Aprendizaje, SENA). Similarly, the body of available material for professionals and informal builders, such as handbooks and design guidelines [61,62], never suggest wood and earth-based Bahareque versions (Bahareque de Tabla and Bahareque de Tierra). As reported in the Manual of Evaluation and Rehabilitation of Bahareque Housing annexed to the Colombian building code, contemporary Bahareque Encementado is the sole reference for the rehabilitation of all damaged Bahareque buildings, even those in Bahareque de Tierra or Bahareque de Tabla. The new anti-seismic code requires all new bamboo buildings to be built in Bahareque Encementado [61]. Thus, the only Bahareque version accepted by the Colombian building code presupposes the filling of the bamboo structure with non-natural material such as cement mortar and steel mesh. Moreover, in the scientific literature and technical reports, the term ‘Bahareque’ is increasingly used as an equivalent to ‘Bahareque Encementado’, neglecting other versions of Bahareque (e.g., [51]). The omission of the traditional versions of Bahareque is neither explicitly motivated nor discussed. As will be seen below, these exclusions are connected to the current validation systems of validation of building materials, which are unable to properly evaluate natural materials and thus privilege engineered materials [35,42].

Aside from these issues, traditional bamboo housing advantages are progressively being acknowledged officially. However, the dissemination of bamboo housing necessitates the inhabitant’s active engagement. As this study will show, misperceptions about the value of bamboo and negative assumptions about its use can hinder or entirely impair any institutional effort for the diffusion of sustainable bamboo housing.

3. Materials and Methods

This interdisciplinary study investigates the construction and habitation of the Colombian informal settlement of Nueva Esperanza, and explores the inhabitants’ perceptions and misperceptions about bamboo, and their effects on material used and design choices. According to the perspective adopted, the bamboo self-constructed dwellings in Nueva Esperanza are understood not only as the result of the available resources and contingent needs of the community’s inhabitants, but rather as a synthesis of contingency with the inhabitants’ needs and intentions, stemming from the notion that design is the translation of intentions and values into physical space [63]. Accordingly, both the material characteristics and technical deficiencies of the buildings—defined as discordances with anti-seismic code indications [53]—were analyzed in order to access the shared imaginary, opinions and preferences of the inhabitants. Such an approach places this study within a body of research on the identitarian and social implications of self-building and manual practice [64,65,66] and draws on social representation theory which recognizes the active role of inhabitants in the selection of references that guide choices and practices and the composition of a common lexicon [33]. Investigating the intentions of the inhabitants is here considered essential for the development of any upgrading strategy, since the inhabitants will be the target audience for future interventions.

3.1. Case Study: Nueva Esperanza

The informal rural district of Nueva Esperanza is located in Colombia, in the Paisaje Cultural Cafetero region about 700 m above sea level in the equatorial belt (see Figure 1 and Figure 2). The occupied area of the settlement is on the edge of the Pan-American Highway and is part of a land previously owned by drug traffickers. Once confiscated, the area was soon abandoned, then taken by illicit dealers and illegally subdivided and sold. In 2013, the defrauded lot buyers decided to occupy the area, followed by people from other regions, thereby founding the Nueva Esperanza settlement. The act of occupation was documented in the local press, e.g., by La Patria and El Tiempo.

Nueva Esperanza’s inhabitants have successfully organized to address internal needs and to make up for the absence of a municipal administration, adopting regulations for community life. Every one or two years, the inhabitants elect members of a council referred to as ‘la Fundación’, to act as liaison with the authorities and institutions in the process of legalizing the settlement and recognizing the property rights of the occupants. Additionally, ‘la Fundación’ coordinates internal activities, organizes public events and awareness-raising projects, and works on introducing essential services into the community.

‘La Fundación’ regularly solicits a census, aimed at building a comprehensive picture of both the inhabitants’ and the state of the housing units. The census is carried out every two years, with forms asking inhabitants to list the occupants, materials used in construction, any changes of ownership, and the state of maintenance for each building. The information reported by the inhabitants is verified by the members of the council and therefore is considered a reliable dataset on the community. Based on the Fundación’s 2017 census, there are about 370 lots in Nueva Esperanza, with 282 households who participated in the survey, namely those involved in the legalization process of their housing units. During fieldwork research, access was given to census data, which was later analyzed to gather more information on the inhabitants of Nueva Esperanza and their housing conditions (Table 1).

Only 203 of the 282 housing units (72%) were permanently inhabited. The other units, often only partially built and occasionally occupied, were recorded in order to potentially legalize them in the future. Our census data analysis focuses only on the 203 permanently inhabited housing units. As shown in Table 1, two thirds of the 203 units (66.5%) have been owned by the same owners since the foundation of the settlement. The remaining third of the units have either been bought from the original owners (20.7%) or have been transferred to current inhabitants as a donation from a relative or friend (12.8%). The 203 housing units are inhabited by a total of 519 people. The average number of occupants for each unit is 2.6 people, ranging from one single dweller (32%) to seven dwellers per household (2%).

Colombians, on average, are younger than Global North nations’ populations but are not the youngest among Latin American populations. The structure of the population of Nueva Esperanza is consistent with that of the whole of Colombia, having a very similar median age (31.3 vs. 32.2 years). As shown in Table 1, one fourth of the population of Nueva Esperanza is less than 15 years old, and almost three fourths of the population is less than 45 years old. The elderly (65+) are very few in Nueva Esperanza, being only around one twentieth of the entire community.

The educational level of the population in Nueva Esperanza is generally low. Apart from children in preschool (7.5%) and people who are currently studying (20.8%), almost another third of the entire population has no educational qualification (29.7%). The remaining population has some educational qualification, but most only graduate from primary school (27.5). The census did not allow a gender analysis of the population. When asked about their profession, more than a fourth of the people of Nueva Esperanza describe themselves as homemakers (26.4%). Two out of five inhabitants are studying (21.3%) or have an agriculture related job (21.3%), while only a small percentage is working in construction (6.2%).

The census also included data showing the wide heterogeneity of building materials used in the housing units, mainly for wall cladding and the finishing of interiors. This data will be further illustrated in Section 4.1 and discussed in relation with the conditions of the housing units and the social representations of inhabitants.

Table 1. Data about the households living in Nueva Esperanza and their housing units. Source: ‘La Fundatión’ census, 2017.

Total n. of housing units	282	100%			Cladding materials in housing units (n = 197)
permanently inhabited	203	72%			esterilla	193	98.0%
not permanently inhabited	79	28%			plastic sheeting	139	70.6%
					metal sheeting	116	58.9%
Ownership status of permanently inhabited units					wood	31	15.7%
owned since foundation	135	66.5%			bamboo culms	17	8.6%
bought	42	20.7%			fabric	17	8.6%
received	26	12.8%			plasterboards	6	3.0%
	203	100%			raw earth	3	1.5%
Total n. of dwellers in permanently inhabited units
	509
					Profession
Dwellers per unit					homemaker	124	26.4%
1	65	32.0%			student	105	22.4%
2	51	25.1%			employed (agriculture)	100	21.3%
3	36	17.7%			employed (other)	71	15.1%
4	26	12.8%			employed (construction)	29	6.2%
5	15	7.4%			self-employed	16	3.4%
6	6	3.0%			unemployed	14	3.0%
7	4	2.0%			retired	5	1.1%
	203	100%			other	5	1.1%
Average dwellers per unit	2.6					469	100%
	N. Esperanza		Colombia
Median age	31.3		32.2
Age groups			cum.%		Education
0–14	128	25.3%	25.3%		preschool	38	7.5%
15–22	67	13.3%	38.6%		studying	105	20.8%
23–44	178	35.2%	73.9%		no qualification	150	29.7%
45–64	104	20.6%	94.5%		primary school	139	27.5%
65+	28	5.5%	100.0%		secondary school	23	4.6%
	505	100%			middle school	50	9.9%
						505	100%

Table 1. Data about the households living in Nueva Esperanza and their housing units. Source: ‘La Fundatión’ census, 2017.

Total n. of housing units	282	100%			Cladding materials in housing units (n = 197)
permanently inhabited	203	72%			esterilla	193	98.0%
not permanently inhabited	79	28%			plastic sheeting	139	70.6%
					metal sheeting	116	58.9%
Ownership status of permanently inhabited units					wood	31	15.7%
owned since foundation	135	66.5%			bamboo culms	17	8.6%
bought	42	20.7%			fabric	17	8.6%
received	26	12.8%			plasterboards	6	3.0%
	203	100%			raw earth	3	1.5%
Total n. of dwellers in permanently inhabited units
	509
					Profession
Dwellers per unit					homemaker	124	26.4%
1	65	32.0%			student	105	22.4%
2	51	25.1%			employed (agriculture)	100	21.3%
3	36	17.7%			employed (other)	71	15.1%
4	26	12.8%			employed (construction)	29	6.2%
5	15	7.4%			self-employed	16	3.4%
6	6	3.0%			unemployed	14	3.0%
7	4	2.0%			retired	5	1.1%
	203	100%			other	5	1.1%
Average dwellers per unit	2.6					469	100%
	N. Esperanza		Colombia
Median age	31.3		32.2
Age groups			cum.%		Education
0–14	128	25.3%	25.3%		preschool	38	7.5%
15–22	67	13.3%	38.6%		studying	105	20.8%
23–44	178	35.2%	73.9%		no qualification	150	29.7%
45–64	104	20.6%	94.5%		primary school	139	27.5%
65+	28	5.5%	100.0%		secondary school	23	4.6%
	505	100%			middle school	50	9.9%
						505	100%

3.2. Research Design

The present interdisciplinary study is based on a dataset produced through a series of field visits conducted between August 2017 and January 2018, combining the structured observation and in-depth interviews [67,68]. These two qualitative research techniques were selected as the most appropriate means to elicit valid and productive hypotheses concerning underlying social and cultural processes. Interviews and observations act as complementary tools to arrive at an analysis of both the physical features of the self-made buildings of Nueva Esperanza and the practices and perceptions of its inhabitants. The information produced from our surveys was combined with data we elaborated from the 2017 council census.

Upon initial observation, recurrent methods of self-design, self-construction, and usage patterns of the settlement’s buildings were identified. The analysis was then restricted to 32 residential units, selected as representative of both the most common building types and the most interesting material combinations. In subsequent visits the metric survey was conducted and the buildings were documented with photographs, sketches, CAD drawings, and functional diagrams of internal distribution (Figure 3). The inhabitants of the 32 selected dwellings were interviewed, with interviews lasting a minimum of 30 min, recorded on site and then transcribed. The interviews corroborated or altered the validity of preliminary hypotheses which emerged during the observation phase, and explored the conceptual categories and interpretations of the inhabitants’ imaginary, concerning both the use of bamboo and housing.

The interviews investigated three macro themes: (i) description of the dwelling and materials used; (ii) construction methods and choices; (iii) future intentions for alterations to their house. All interviewees were asked to narrate the construction process of their house, illustrating the methods, actors, time, material, and financial resources employed, and the degree of their possible involvement. The inhabitants also illustrated the dynamics of habitation, and the internal functional layouts of their houses, explaining their choices in terms of cladding solutions, furniture, and decoration. Finally, the respondents were asked to indicate how they intended to fix, renovate, or transform their homes. Across the three macro themes, we investigated the inhabitants’ perceptions regarding the use of bamboo, the main topic of interest in our research. We asked the inhabitants whether and how familiar they were with the material, their reasons for choosing it, methods of bamboo treatment and alteration, overall satisfaction, and whether they planned to use it in the future.

The transcriptions of the interviews were coded and analyzed [68] to identify the main themes that structure the preferences of Nueva Esperanza’s inhabitants. The following section highlights the results of this analysis.

4. Results

The structured observation conducted in Nuova Esperanza provided an overall picture of the settlement’s dwellings, their state of preservation, stylistic choices, and technical solutions. Interviews with inhabitants illuminated the relationship between the builders’ knowledge and the quality of the dwellings, as well as the link between the inhabitants’ choices and their perceptions of the house, i.e., the form and materials of the house and the meanings associated with them. Section 4 reports the results of the survey on Nueva Esperanza, in a thematic analysis.

4.1. Features and Weaknesses of the Dwellings of Nueva Esperanza

The houses in Nueva Esperanza are built in bamboo on basic lots of either 6 by 8 m or 8 by 10 m. Starting from this size matrix, each family freely decided how much area to build and whether to build one or two floors. All of the surveyed inhabitants designed their houses themselves, as these interviewees explain:

We designed the house ourselves, more or less. [F60] (Respondents’ gender and age are tagged at the end of each verbatim quote from interviews)

I commissioned the construction of the house, but I did the design. [F49]

The utilization of self-design allowed the inhabitants to autonomously make choices on the distribution of space, the internal organization of the dwellings, and on stylistic and embellishment solutions. As a result, the settlement presents a wide range of distribution layouts (Figure 3).

In spite of their variability, the dwellings of Nueva Esperanza share common design problems. Most buildings display signs of widespread decay, structural instability, and rapid material deterioration.

The same heterogeneity in the internal organization of the dwellings is also present in the use of materials. Although all of the 203 inhabited buildings in Nueva Esperanza possess a bamboo —specifically Guadua angustifolia Kunth— load-bearing structure, they have different cladding and covering solutions involving different materials, as also pointed out by the 2017 census data (see Table 1). Roofs are made of sheet metal and plastic panels, while wall claddings are made of Guadua mats (Bahareque-style ‘esterillas’) and plastic sheeting, as well as plasterboard, raw earth, wood, sheet metal, or other reused elements. The entrance façades and the most visible external walls have distinctly different treatments from the other perimeter walls: they may be painted, clad in more valuable materials, or even be the only ones clad (Figure 4). Plasterboard, for example, is in no case applied on the entire outer shell of the building, but only on the front facing the street.

None of the dwellings meet the requirements of anti-seismic design and most have irregularities, weak points, ineffective bracing and foundation systems. Bamboo culms are cracked due to poorly distributed loads. Bare bamboo is damaged because of the exposure to sun and weather and the lack of protective elements from ground humidity. The state of conservation of the ‘esterillas’—the bamboo mats used in Bahareque tradition—shows inaccuracy in the cutting and installation processes.

The mechanical performance and durability of bamboo was damaged by poor treatment, design choices and an inconsistency between the possibilities and the actual use of the material. This contrast is particularly evident in cladding treatments. Different covering solutions employed in internal and external walls of Nueva Esperanza buildings do not safeguard the resistance, ventilation, and comfort that traditional Bahareque could afford (see Section 2.3). In Nueva Esperanza, the Bahareque-style ‘esterilla’ mat is by far the most common cladding solution (98%, see Table 1). However, in most cases ‘esterilla’ is further coated with impermeable plastic sheeting (70.6%), sometimes recycled from advertising posters or packaging. Elsewhere, the structures are cladded with other materials not permeable to air, such as plasterboard, which when nailed to bamboo canes can cause them to break. These cladding materials prevent air circulation, thus raising indoor humidity and temperature (Figure 5).

Indeed, different cladding choices produce extremely significant consequences on housing comfort, and in Nueva Esperanza it was immediately evident when entering the spaces. The single house covered with raw earth, mud and straw, offered the visitor a cool environment, and in the few houses covered solely with bamboo mats, there was light ventilation. In contrast, the use of plastics and plasterboard created indoor spaces characterized by a moist heat and stuffiness, making habitation more difficult. Given Nueva Esperanza’s location in the tropics, the impact of construction techniques on indoor comfort is easy to perceive, because heat and lack of air circulation can quickly produce suffocating and unhealthy environments. Yet the most common cladding solutions neither seek nor favor the comfort of interior spaces, but rather pursue other aims. In order to access some of the reasons behind the composition of Nueva Esperanza housing, it was useful to recall the genesis and development of the settlement, which is the second theme addressed in the interviews with the inhabitants.

4.2. From Collecting Bamboo to Self-Building

The availability of a resistant material at no or low cost is strategic in informal housing. In the Paisaje Cultural Cafetero, bamboo forests and cultivation are widespread and accessible, and farmers usually collect and stock bamboo canes in order to have material at their disposal. Consequently, finding bamboo canes, both fresh and already dried, is not difficult, especially for those who work or have contact with local ‘fincas’ [farms]. It is not by chance that bamboo is present in all of the buildings of Nueva Esperanza. Almost all of the surveyed inhabitants state that they built their houses out of bamboo precisely for the above reasons: availability, ease of access, and affordability. In some cases, the material was recovered from the workplaces of the inhabitants, in others it was harvested from the bamboo forests:

Bamboo and Guadua are common here … [F36]

I got so much Guadua easily because of my job on the farm. [F45]

The material with which I made my house was given to me as a gift, because of my work. [M58]

According to the inhabitants, bamboo is seen as abundant, available, and most importantly, free. Even when they had to incur construction costs and pay for materials, bamboo was not an expenditure item:

To pay the construction costs, I sold my cow. I bought the material and I cut the wood [and the Guadua] myself. [M53]

We paid a master builder to build but we took the material from the ‘quebrada’. [F34]

Another perceived advantage of bamboo is its versatility and intuitive ease of use. According to the surveyed, the basics of bamboo building, relating to cutting, tying and making joints, are easy to learn and relatively accessible, especially for those working in agriculture:

Living in the countryside, and in farms, one learns at a young age how to build handicrafts. […] People know how to work bamboo and Guadua. [M37]

As in most informal housing episodes, the vast majority of houses in Nueva Esperanza are self-built. Most of the surveyed people built their own houses or those of their relatives, and only a few were commissioned from external professionals. Some inhabitants had professional or semi-professional skills, and two of the surveyed had attended Bahareque construction training courses offered by the National Training Service (see Section 2.3). In general, in informal settlements, three factors discourage people from outsourcing the construction to professionals on the market: the scarcity of available economic resources, their precarious legal condition and the urgency of construction. In Nueva Esperanza, as we have seen, self-building was also favored by the availability of bamboo.

The surveyed inhabitants hold ambivalent attitudes towards the experience of self-construction, with many heralding its ability to bring the community together and foster solidarity, but simultaneously lamenting the immense amount of effort required. On the one hand, autonomy in design allows them to build a closer and more personal relationship with their home, as seen in the spatial customizations. Moreover, the self-building process is often recalled and recounted with pride, and there are those who have documented the different stages of construction with pictures and films, such as this woman, who proudly showed videos of the construction of her home while recounting the process:

My husband left his job and with the settlement he bought the materials to build our house […] If you want we can show you some videos of the construction of the house. [F59]

Alongside feelings of self-fulfillment, inhabitants elaborated how the construction of their own house brought family members and neighbors together in novel ways. In some cases, self-building has allowed the emergence of spontaneous forms of solidarity and support among the inhabitants of the settlement, even in the absence of already established relationships, as the following comment shows:

I built the house myself, I started building before I met my husband. But the neighbors saw me working alone and helped me a lot. [F30]

This cooperation found between residents in construction also extended to a shared commitment in the maintenance of the community’s public and shared spaces. Interviewees recounted that several members of the Nueva Esperanza community actively contributed to the repair of roads, the creation of urban furniture and the beautification of common areas.

Yet, despite these affirmative points, according to some inhabitants, self-building is a laborious practice. Handcrafting components of the house is a tiring activity, requiring time, physical effort, and even causing pain. The following quotations portray self-building as necessary but painful:

My husband and I built the house where we live now in the settlement, we made the mats ourselves, which is very difficult and very hard. [F25]

We [mother and daughter] did the construction of ‘esterillas’ ourselves. We had no idea how to do it. I hurt my hands every weekend. [F39]

The laboriousness of the self-building processes is closely linked to the level of training of the inhabitant-builders: the less experienced they were, the more grueling the work turned out to be. Furthermore, the degree of training and technical knowledge of the inhabitant-builders proved to be central not only for the duration and intensity of the construction, but even for the quality of the handmade buildings. Among the inhabitant-builders of Nueva Esperanza, some had already gained experience in bamboo construction due to previous professional experience, as in this case:

I built it myself because I know how to work the Guadua, I’ve been doing it for 22 years. [F46]

However, most of them improvised as self-taught builders out of necessity, as explained below:

We built the house by ourselves… We learned how to work the Guadua. [F33]

Self-building by those who were self-taught without adequate preparation compromised the state of preservation of the dwellings, as could be observed during inspections. The absence of prior material processing caused the deterioration of mats, early cracking, and the rotting of bamboo culms (see Section 4.1). In some cases, moreover, self-taught builders freely adapted techniques singular to other materials and applied them to bamboo construction. For example, one interviewee justifies the transfer of construction practices from wood to bamboo by making an implicit and groundless assimilation between the two materials:

My husband built the house in Guadua as an autodidact, as he knew how to build in wood. [F47]

On the contrary, using bamboo as if it were wood has affected the durability of many houses in Nueva Esperanza, causing fracturing and crushing of the canes of the supporting structure. Thus a lack of knowledge of the material and its required processes prevents its potential from being realized. Even those inhabitants who are informed about bamboo and the requisite processes to make it a reliable and durable material, have given up on the enhancement of the material. This inhabitant, for example, due to his profession knows the quality of properly treated bamboo architecture and is aware of the value that a bamboo house can have when constructed properly for an affluent and cultured recipient:

A German who lives in Medellín asked for a house in Guadua, but in that case they cut it well and at the right time, they treated it before, they immunized it very well, and so on. [M45]

Yet, he did not consider it appropriate to apply this knowledge in the making of his own home, which in fact he described as prone to structural deficiencies:

This house, as it is will not last more than 5 years, because it wasn’t treated and cut well.

This example shows how the under-utilization and mis-utilization of bamboo does not only result from a lack of education. As we will see in the following sections, it can depend on other kinds of reasons.

4.3. Bamboo and Housing Models in the Inhabitants’ Expectations

The processes of housing upgrading and the legalization of informal settlements usually involve the disbursement of public funds to residents to rebuild their homes. In Nueva Esperanza, where the prospect of legalization is considered very plausible, the inhabitants shared their expectations concerning receiving such subsidies. Based on the eventuality of monetary aid, they have drawn up personal resolutions to fix up or convert their current homes. The expectations related to this future phase of the settlement are the third topic of the interviews (see Section 3.2) and are particularly useful in ascertaining inhabitants’ preferences and their relationship with bamboo as a building material.

For Nueva Esperanza’s surveyed inhabitants, the ideal post-legalization house is frequently imagined as having a garden, a balcony, a room for each person, and be two-storied. In almost no scenario is bamboo kept as a building material, either for the structure of the house or for cladding. Rather, most interviewees say they intend to employ any public aid to construct a new masonry or concrete building. Therefore, in the stabilization phase of the settlement, bamboo will be written off. Even the words they adopt reinforce the preference for concrete and masonry at the expense of bamboo, as these excerpts show:

We have been here since the beginning and we want the legalization to change the house ‘en material’. [F47]

We hope that with the legalization we will receive some help from the Government [meaning State], with which we want to build ‘en material’. [M60]

In the interviewees’ words, the masonry house and the reinforced concrete house are merged in the expression ‘vivienda en material’, literally ‘material house’. With this lexical choice, the inhabitants reveal two beliefs: first, that the two techniques, masonry and reinforced concrete, are interchangeable. Second, that masonry and reinforced concrete are the quintessential building techniques, so much so that it is possible to identify them with ‘the materials’. In contrast, bamboo, earth, and wood-based construction techniques are secondary and marginal options.

Only in a few isolated cases interviewees state their intention to live in a bamboo house even after legalization:

What we will do with the legalization would be to build in plastered Guadua, because that is the ideal solution […] it resists so much to earthquakes that absolutely nothing happens to it. [F60]

Nevertheless, this is a negligibly held position. Although the reasons for choosing bamboo in the first phase of the construction are seen by many as valid, the intention to abandon it in the reconstruction phase of the settlement is by far the most common attitude among Nueva Esperanza inhabitants.

4.3.1. Perceived Safety and Durability of Bamboo

The intention to write-off bamboo after legalization reveals inhabitants’ perception of it as a building material unequal to cement and brick, both in terms of mechanical performance and its appropriateness as a constitutive element of a ‘proper’ house.

The primary reason given among inhabitants for the supremacy of masonry and cement over bamboo stems from the perceived superior resistance of those materials to weather, catastrophic events, and for general ‘safety’ reasons. The alleged lack of ‘safety’ of bamboo is a recurring argument in the choice to replace it during reconstruction. See for example the following passages:

But I would change [bamboo] for ‘material’ or adobe, because it is ideal against hurricanes. [M45]

We want to convert the construction to one ‘en material’, for safety. [F33]

We do know that Guadua is very good for building … but the ‘material’ is safer. [F55]

Upon further questioning, none of these opinions on the performance of bamboo are corroborated by the inhabitants’ direct experience, and are indeed at odds with evidence from the scientific literature and building traditions, which have proved bamboo buildings to be structurally reliable and resistant to natural disasters [42,55,69]. In presenting their preference for other materials besides bamboo, the surveyed people do not feel compelled to adduce any evidence. Only one interviewee who considered living in a bamboo house in the future based her opinion on personal experience. She defined bamboo housing as durable, cool, and most importantly cheap enough to be built with little money. To support her opinion, she presents her father-in-law’s experience of living in a bamboo house for a long time:

Guadua can be very resistant, and I like it better than other materials, because the Guadua house is cool. […] My father-in-law lived in a two-story Guadua house that resisted as it was for 20 years. [F25]

However, her father-in-law, although he had been satisfied with his bamboo house, decided to replace it. Once he received public aid, in fact, he chose to build a masonry house. However, as the woman recounts, there were not sufficient funds to finish the construction:

When the State gave him the money so that he could exchange it for material, the budget was not enough to finish it and it still has no roof.

This apparently paradoxical episode is actually indicative of the strength that the masonry house has in the collective imagination of informal settlement dwellers. The appeal of a ‘material house’ clearly outweighs even the direct experience of the advantages of bamboo construction.

4.3.2. Bamboo Housing as a Temporary Condition

Another theme that emerges from Nueva Esperanza’s dweller-builders for the post-legalization phase is the expectation of a “vivienda digna”, that is a “decent, acceptable house”. As this interviewee clearly states, an acceptable house is what inhabitants aim to obtain from the settlement upgrading intervention:

We are waiting for legalization so we can have a ‘vivienda digna’. [M45]

A formal house is the one presumed to be permanently inhabited: no longer squatted but owned, and acceptable, thus meeting the minimum requirements for resistance, size, and decorum. Therefore, the category of housing acceptability has mechanical, legal, but also aesthetic and, above all, semantic declinations. By commenting on other houses in the settlement, and showing appreciation for some specific elements, the interviewees revealed the features of what they consider an acceptable home: the quality of decorations, the smoothness of the surfaces and the uniformity of color. For example, façades clad in painted plasterboard are preferred because of their likeness to ‘material houses’ (see Figure 4, above), as this man states:

Have you seen that house? They made it very well, it looks like a material house. They are the best [you can find] here. [M47]

Again, masonry-cement is the principal referent of the imagined proper house, even in aesthetic terms. In the imaginary of Nueva Esperanza’s inhabitants, the acceptable house coincides with the house ‘en material’. The dweller-builders sought the homogeneity and smoothness of walled exterior and interior surfaces because of their similarity to plastered masonry or cement constructions. This finding supports the hypothesis that the choices of wall covering materials had semantic rather than comfort and performance-related reasons.

Hence the bamboo structure is concealed, reduced to a supporting medium for another exterior form; the ‘esterillas’ bamboo mat claddings are sometimes painted, but more often hidden behind other materials. As Figure 5 shows, the favorite additional finishes to ‘esterillas’ are plasterboard, concrete, and particularly plastic tarps, which are all materials that are homogeneous to the eye. They are regularly employed, despite the fact that, as mentioned above, they are incompatible and even harmful to the bamboo frame (see Section 4.1). In particular, the use of plastic tarp, which allows for a continuous and regular surface and is a cheap and easy-to-process material, prevents the structure’s ventilation of interior spaces, creating a stifling and unhealthy environment. Yet, as this man explains, it is compatible with the quest for surface uniformity:

It’s all wrapped with ‘lona’ [tarp], we also put it on the ceiling, so it’s ‘todo igualito’ [all the same]. Where you can see the cardboard is because I have to change it. [F49]

In Nueva Esperanza, dwellings of walls clad with plastic tarps are extremely common, and often treated with great care, decorated with drawings and appliqués or framed with slats (see Figure 5). The widespread use of plastic, plasterboard and concrete in spite of their issues is thus related to the desire to reproduce at least in part the look of a house ‘en material’.

These findings show the significant gap that exists between bamboo construction, its perception and the collective idea of a ‘proper’ house ‘en material’. Investigating this discrepancy is key to understanding issues related to the recovery of bamboo and the problems around reintroducing it into informal settlements and other social contexts.

5. Discussion

5.1. Bamboo Housing and the Life Stages of Informal Settlements

The data collected through the observation sessions and in-depth interviews made it possible to identify some of the main aspects of the relationship of Nueva Esperanza inhabitants with their homes: in particular, their construction and housing choices. The analysis was conducted by reconstructing the different moments in which these choices were made, with a projection also towards the future. This framework was established based on a general life cycle that most informal settlements undergo [20], that consists of three phases: genesis, appropriation, and reorganization. In each of the phases, the degree of housing development changes, as does the availability of services and the ways in which the community is organized. This is closely related to the resources available to inhabitants, but also to the nature of their aspirations, which in turn is related to their perception and received knowledge.

At the time of the survey, Nueva Esperanza was in the second phase of the informal settlement’s life cycle, that of ‘appropriation’. Appropriation is the transition phase between the initial emergency condition and the reorganization phase, which involves public aid and permanent residence or possible relocation elsewhere. Analyzing Nueva Esperanza at this stage allowed us to investigate the other two phases as well, both by going backwards to the origins of squatting in the area, and forwards in projecting the settlement’s future based on inhabitants’ perceptions of their homes and community. As discussed in Section 3.2, this chronological reading was guided by a precise research design, i.e., to analyze the construction and housing choices in Nueva Esperanza as a case study, in order to investigate perceptions about the use of bamboo as a building material.

5.2. The Vicious Circle of Bamboo as a Transient Material

There are different reasons for building a house in an informal settlement. For some it is a way to solve a pressing housing need; others build in search of property rights that eventual legalization brings. Whatever individual motivations for moving to and building in an informal settlement, it is the availability, low cost, and the chance to build quickly and independently that guide the choice for materials and house construction techniques. In Nueva Esperanza, bamboo was chosen because it met all of these needs and, being so widely present in the area, it was familiar to the inhabitants. It is therefore no coincidence that bamboo is the main structural building material of all the houses in Nueva Esperanza. Moving beyond the installation phase, interest in bamboo gradually declines. The results presented in Section 4 show that bamboo buildings in Nueva Esperanza are not designed to be durable, but to provide shelter for a short time. Although bamboo is environmentally sustainable and performs well in terms of seismic resistance, climatic comfort, and inhabitant well-being (see Section 2.2), it is considered a transient material. This assumption has wide-ranging consequences on the relationship and use of bamboo by the community.

In the genesis of the settlement, bamboo was widely utilized and some of its advantages were acknowledged, but the factors that led to its association with transience were already present. This was largely a result of superficial or inadequate knowledge of the material’s properties, which became particularly problematic in the self-construction process. Basic knowledge of the necessary bamboo treatments and techniques, although simple and potentially easily accessible, are essential to take full advantage of the material. Not carrying out preventive treatments reduced the material’s durability, just as adopting construction techniques peculiar to other materials (such as wood) led to its deterioration. The compromised state of Nueva Esperanza houses less than five years after their construction is due to the negligence of dweller-builders, but also to their lack of interest in the material.

Inhabitants did not take any measures to maximize the performance of bamboo, in part because they did not consider it worth investing resources and time in a material to be quickly replaced. In so doing, they took part in a self-fulfilling prophecy of confirming bamboo’s ostensibly greatest weakness, i.e., its lack of durability. In fact, in Nueva Esperanza the short life expectancy of the houses discouraged inhabitants from paying attention to bamboo processing, leading to rapid deterioration and a negative attitude towards bamboo buildings. Yet, as discussed in Section 2.2, perishability is not an inherent property of bamboo buildings: when properly assembled they are high performing and withstand the ravages of time, extreme weather events, and earthquakes. It can be argued then that the limitations of Nueva Esperanza’s bamboo buildings depend directly on the shortcomings of the community’s own builder-inhabitants, who are incidentally bamboo’s first detractors. The use of bamboo architecture in Nueva Esperanza is not indicative of bamboo’s potential as a building material, but the poor preservation of their houses bolsters the belief and perception that bamboo is not durable and unsafe. This ends up fueling a vicious cycle discouraging interest in bamboo housing from which it is difficult to get out.

This association of bamboo as a temporary resource is carried into the second phase of settlement, the so-called ‘appropriation’ phase. As confirmed in the interviews, ‘appropriation’ is also a transitional phase, which foreshadows legalization and thus the possibility of making a finalized and non-temporary home. The expectations toward the latter phase orient many of the choices made in the appropriation one: in Nueva Esperanza they motivated the decision not to invest time and money in the consolidation of the bamboo of the house structures but rather to prepare for its replacement with other building techniques and materials. Such choice confirms how bamboo is judged to be an inferior material, relegated to temporary use.

5.3. Abandoning the Tradition of Bahareque

The misperceptions that Nueva Esperanza’s inhabitants have of bamboo are particularly significant in view of the socio-cultural and geographical context of the settlement. It should be remembered that Nueva Esperanza is in a region whose relationship with bamboo is neither recent nor imported. Indeed, the presence of bamboo and the territorial features of the Paisaje Cultural Cafetero have fostered over time the development of the building tradition of Bahareque, whose importance was highlighted in Section 2.3.

Bahareque meets all of the structural and contextual requirements of the area in which it originated in terms of earthquake resistance, ventilation, cost effectiveness, easy construction, and environmental sustainability. In development and tropical contexts, all forms of Bahareque, including Encementado, has been shown to have equal or lower cost of other forms of low-cost housing [56], since bamboo-based techniques are cheaper than masonry, concrete, wood, and steel ones [70]. Moreover, its use of plaster finishes makes it similar to other types of conventional construction. Therefore, it is crucial to understand why in the place where Bahareque flourished, bamboo is no longer perceived as a valid building material by the local community.

Our empirical research attempts to answer this question by analyzing the testimony of community members and their ways of building, modifying, and inhabiting their homes. The investigation of this underlying social reality is systematically ignored in projects and policies that attempt to recover bamboo as a building material, and should therefore be introduced as a method to provide a useful social and cultural context for the diffusion of more sustainable housing.

5.3.1. Globalization and Social Representations

The modus operandi of Nueva Esperanza’s inhabitant-builders in the construction of their homes was not necessarily focused on climate comfort, earthquake resistance, and environmental sustainability, all of which would be rewarded by local traditional bamboo housing, i.e., Bahareque (see Section 2.2 and Section 2.3). Prior to a consideration of these factors, their choices responded to the function of meaning [71] and cultural appropriateness [7], according to references shared and recognized by the group. The materials, finishes, and furnishings that the inhabitant-builders of Nueva Esperanza have adopted in their bamboo houses should be read as signs that refer to meanings inscribed in space [72]. Choices in the treatment of interior or facing walls were mainly dependent on their visibility [73] because it is primarily through visibility—to oneself and to others—that a signifier becomes signified, and a meaning is produced. As emerged from the interviews, the referent for evaluating the best possible housing solutions was the house ‘en material’, built of brick or concrete. They contrasted the local and traditional Bahareque techniques with the abstract and universal model of the masonry-cement house, which is selected without even taking into account climatic and environmental conditions. Plastic sheeting and plasterboard used to buffer walls or cover ‘esterillas’ worsened the livability of the homes. However, this was less relevant than the fact that such materials make the walls more similar to those of ‘material’ houses.

The gap between the opportunities provided by bamboo and its use in Nueva Esperanza also depends on the different meanings attributed to bamboo. Experts and policy makers now see in bamboo housing an opportunity for sustainability, accessibility, and equity, encouraging the application of bamboo to solve housing needs, especially in tropical fragile contexts. Moreover, what Nueva Esperanza inhabitants see in bamboo housing is marginality, poverty, and transience, and this belief is reinforced by their observation of the limited application of bamboo in high-end formal settings, such as city centers and affluent neighborhoods. In fact, academic research mainly discusses non-engineered bamboo in relation to housing issues for marginal and low-income communities, and it is in such contexts that bamboo housing has been promoted [40,74]. Nueva Esperanza residents’ opinion of bamboo is thus eroded by its perceived exclusive connection to local and traditional practices, and distance from the abstract but appealing globalized image of masonry-cement. Bahareque tradition is lost, and no longer corresponding to the norm and established practice, therefore bamboo resides outside the collective imaginary as an acceptable building material for housing. While the use of concrete is read as a sign of modernity, bamboo is interpreted as part of an antiquated building tradition. This explains the cultural resistance to the use of bamboo, except as a temporary resource.

In Nueva Esperanza, the transformation of the community’s shared imaginary regarding the home must be read, in a broader perspective, as the result of the shift from traditional to modern times and values. As with all traditional techniques, Bahareque originates from the interaction between a community and its environment, through dynamic adaptations to external constraints and climatic conditions [65,66,75]. By contrast, modern building knowledge is detached from specific social groups and geographies, transferred instead to an abstract and universal plane [65], where interest in the specificities of local context and resources is not preserved [76]. As a result, these repertoire of building practices nurture forms and images of the home typical of a globalized and modern culture, often not compatible with local needs [8]. This process of abstraction and standardization produces a homogenization of design [28] and thus of references that can be read in the social representations of the inhabitants of Nueva Esperanza.

5.3.2. The Effects of the Standardization of Building Practices

Alongside the use of bamboo, the practice of self-building links Nueva Esperanza’s informal housing to traditional building cultures. In the sphere of traditional practice, technical knowledge is shared and self-construction is fundamentally a collective practice and a form of education, interaction, and identity building within the group [64,66,71,77]. In Nueva Esperanza, self-construction met these criteria: inhabitants took advantage of the affordability, speed, and flexibility of this mode of house-building, and while complaining about the intensity of the work required, they appreciated the opportunities for social cohesion and empowerment. However, in their perspective the value of self-construction is limited to the informal dimension. Should they have had sufficient resources and time, the inhabitant-builders of Nueva Esperanza would have turned to the construction market, involving specialized contractors and professionals, an attitude found in other informal contexts and emblematic of a shift to modernity [17].

In modernity, design is delegated to experts, building is a monopoly of specialized professionals [65,78], and dwelling takes place in standardized and engineered solutions, designed a priori, and spread globally [7,28]. Construction and dwelling, formerly unified, are now decoupled and deracinated from one another [75]. This derailment of long-established practices engenders a loss of value in the historical and cultural inheritance, magnified by the prestige associated with contemporary industrialized techniques, making low-tech and simpler self-building techniques a secondary and lesser option. In traditional cultures, housing is built by all members of the community, but in modernity, it is only the purview of professionals.

Another issue that contributed to the loss of building traditions such as Bahareque is that the natural materials they employ do not properly fit the current structural engineering practice and its validation systems. As said in Section 2.2, natural materials are heterogeneous and determining their resistance factor or any other standard coefficient of structural behavior is a long and complex technical process [35]. In the traditional culture in which the Bahareque was created, techniques were tested locally, by time and events, from generation to generation. Nowadays, instead, traditional building techniques are usually excluded from building codes as the empirical evidence of their anti-seismic performances is hardly received by current material science and structural engineering [78].

The pioneering inclusion of Bahareque in the Colombian building code is certainly a significant advancement in recovering bamboo as a building material. Nevertheless, if critically analyzed, it also reveals to be problematic. Bahareque exists in a plurality of versions (see Section 2.3), all having excellent structural performances [54,55,58,59]. Among them, Bahareque de Tabla and Bahareque de Tierra, the wood and earth versions, are the most sustainable, as they are made only of natural materials: they have a lower carbon footprint; they provide air ventilation, thermal and humidity regulation, thus creating healthier spaces [79]; and their components can be recycled at the end of the building’s life cycle. However, the only version of Bahareque included in Colombian anti-seismic code is the contemporary Bahareque Encementado, in which the basic structure of bamboo is combined with cement and steel mesh—non-natural building materials with a high environmental impact [35]. The exclusion of other versions of Bahareque follows the evaluation criteria which exclusively focus on the adherence to current standards of testing that are conceived and long-optimized for non-natural materials: hence, the addition of cement with steel mesh, and the acceptance of Bahareque Encementado. This reductionist approach to natural materials produces a paradox that is more and more evident nowadays, as building in an environmentally sustainable and resource-saving way is considered a requirement. Despite the rise in sustainable building practices, natural materials are accepted among the regulated and commonly usable techniques only by undergoing sophisticated processing or by being combined with non-natural and non-sustainable materials.

This approach deprives the traditional technique from its ability to respond sustainably to specific context needs and prevents it from truly contributing to the innovation of building practice. Indeed, lessons can be learned from traditions on how to build and design in relation to a fragile environment [14], and such contributions are not limited to technical fundamentals to match with modern standards. Rather, traditional knowledge is a repository of sustainable approaches: it promotes a measured use of local materials and low-tech, energy-saving strategies, such as water management systems which are key to combat desertification [80]; it suggests self-construction as a means to reduce the cost of housing intervention while enhancing community empowerment [8]; it provides a source of practical and collective validation to a wide range of building techniques and materials [7]. Thus, to address current ecological and social challenges, contemporary adaptations of traditional techniques must be inspired by ecology, consideration of context, and the autopoietic approach, which are some of the founding pillars of traditional cultures [76].

5.4. Destigmatizing Natural Materials and the Retro-Innovation of Building Practices

Placed in this historical and socio-cultural framework, the beliefs of Nueva Esperanza’s inhabitants, which, taken at face value even seemed contradictory to their local tradition and geographical contexts, are more understandable. Their skepticism for bamboo as a building material is rooted in the shift from tradition to modernity, both in social representations and building practices, with an attitude of indifference towards local and natural resources in favor of the cult of technology, specialization, and universalization. This shift happened in the course of time and is embedded in systems of signs referring to meanings that are continuously reproduced in many cultural domains. An example of the strength and pervasiveness of these symbolic domains comes from the world of modern fables, where there exists a perfect example of the prejudice toward natural and flexible building materials compared with more modern and stiff ones. In “The Three Little Pigs” fable, the choice to build a house in straw or in wood is presented as a sign of laziness and is the cause of the death of the first two pigs. The only house that is able to withstand the attacks of the wolf is built in concrete and bricks by the third, committed and serious pig. Originating from the cultural world of the British Industrial Revolution [81], this fable spread in many languages and variations, through different media, as well as a widely popular Disney cartoon, and is still subtly affecting the cultural domain of many children around the world, including Latin America. It is worth noting that in a Portuguese version of the fable the weakest house is built precisely of bamboo and straw.

Without taking into consideration the complexity of social representations, recovering and innovating traditional knowledge proves futile. The meanings associated with dwelling and building play a fundamental role in perception, all the more so for the acceptance of innovative proposals, particularly retro-innovation. Retro-innovating does not mean to enhance and standardize traditional techniques producing engineered, industrialized, or prefabricated versions of them. On the contrary, retro-innovation aims to address contemporary issues through the guidance of traditional knowledge, namely applying its system of practices and values to the current context. Standardizing traditional techniques could therefore be construed as, rather than retro-innovation, retro-standardization.

In sum, on the one hand, traditional knowledge and natural materials should be destigmatized in order to be widely adopted by communities, and this is why analyzing the symbolic domains is necessary. On the other hand, the values of traditional knowledge should be fully acknowledged by the institutional actors who have the responsibility to validate building techniques that retro-innovate traditional knowledge.

6. Conclusions

Scientific research has consistently proven that bamboo can be a sustainable resource in the ecological transition, due to its environmental sustainability, low carbon footprint, thermal and moisture regulation, wide availability, low cost, structural resistance, and workability. Due to the outstanding mechanical properties of the material, both in terms of tensile strength and elastic modulus, bamboo is gaining increasing attention in the building sector. Engineered bamboo (e.g., bamboo panels) and bamboo-based composite materials, such as bamboo-fiber-reinforced composite materials, are the promising focus of extensive current research [41,82]. Moreover, bamboo is a common building material in vernacular architecture in many parts of the world. Both these facts could make bamboo building techniques suitable solutions for upgrading programs to improve conditions of the growing population living in informal settlements worldwide. However, this study shows that the path towards a wholesale adoption of bamboo housing is not straightforward and demands adaptations based on specific cultural and social contexts.

This conclusion is supported by the empirical results produced investigating the perceptions and the uses of bamboo in the informal settlement of Nueva Esperanza, which is located in the area where the long-established practice of Bahareque was born and flourished. Bahareque built on the many strengths of bamboo and through simple and self-applied techniques allowed the production of durable, inexpensive and sustainable dwelling units that successfully faced the climate and seismic challenges of the region. Surprisingly though, only five years after the foundation of Nueva Esperanza, all of its bamboo dwellings presented deteriorated materials, which they would not have if built according to Bahareque. The analysis illustrated that the inhabitants of Nueva Esperanza had a much weaker relationship with bamboo than when Bahareque was popular in the region. Interviews revealed that bamboo was adopted only as an emergency and temporary material, for its low cost and availability in the area. Although bamboo had always been familiar to the community, poor application of bamboo building techniques, combined with misperceptions on the utility of bamboo, strongly impacted the quality of the dwellings built and, specifically, their resistance and durability. Moreover, these beliefs and the ensuing practices fed a vicious circle, strengthening inhabitants’ perception that bamboo is not a safe and durable material, and that it can only serve as a transient building material.

Observations and interviews of Nueva Esperanza inhabitants reconstructed the community’s social representations regarding bamboo housing. It was revealed that both building and habitation choices and furnishing options were made for their symbolic value rather than for their functional efficacy, regardless of the negative impact that some choices have on indoor climatic comfort or livability. This was confirmed also by the inhabitants’ views regarding their imagined future housing: whether in Nueva Esperanza or elsewhere, bamboo housing would have certainly been abandoned for what is perceived as a safer and more dignified solution, namely the house ‘en material’, built of brick or concrete.

These views can only be understood considering that, among all dimensions that affect building and housing options, the symbolic is much more relevant in shaping people’s perceptions and choices than the extent acknowledged by policies aiming at reintroducing natural building materials. As discussed, even the pioneering measures taken by Colombian institutions to reintroduce bamboo housing follow a technocentric approach, focusing on standardization protocols that do not optimize the intrinsic qualities of natural materials. This is confirmed, as an example, by the tendency of institutions to validate only contemporary hybrid versions of traditional building techniques—e.g., combining bamboo with cement mortar and steel mesh. And while advancing technical knowledge on bamboo is necessary, this needs to be accomplished with contextualized methods which must not neglect how social representations shape perceptions and housing behaviors. Failing to do so strongly compromises the possibility for bamboo to be used as a viable alternative to other less sustainable building materials.

This research addressed an exemplary case of how the combined effect of cultural globalization, modernization, and the standardization of construction practices have marginalized and are now devaluing traditional knowledge on natural local building materials. Given the social significance of sustainable and accessible housing in informal settlements, we believe that more research is needed: quantitative surveys with a statistically significant sample of houses and inhabitants, both in Nueva Esperanza and in other contexts would help produce more comprehensive and conclusive results. Further research may also consolidate the interdisciplinary framework we adopted in this study, and such a framework would help make the construct of retro-innovation more theoretically refined.

Our study focuses on human and social factors in habitation and architecture, and it can be applied to investigate the relationship inhabitants have with other natural building materials and techniques, also in other urban environments beyond informal settlements. We believe that the expansive field of architecture and building techniques could benefit from the genuine application of retro-innovation. What this interdisciplinary study shows is that investigating perceptions and the underlying symbolic system of social representations shared by a population is necessary to address issues that limit the spread of more sustainable building materials and housing practices.