Sustainable building materials for low-cost housing
There is a huge need for affordable and sustainable urban housing in the countries of the Global South. Below, some sustainable building materials that can be used for low-cost housing are discussed. Housebuilding requires the provision of land, good-quality building materials, labor, and knowledge about house building. Crucial items include the following: 1) local availability of raw materials and labor, 2) cost of raw materials, transportation and manufacturing, and 3) sustainability aspects. The quality of the house’s structure – for example, foundations, frameworks, and joints – must always be carefully considered.
Bamboo is seen as a sustainable building material, but it must be treated well before it can be used for house building. Some other building materials are also seen as sustainable, such as compressed earth bricks and adobe bricks as alternatives for fired bricks, and construction blocks of concrete. Conventional building materials such as iron, cement, and concrete are normally not produced in sustainable ways. Fired bricks are not considered to be ‘sustainable’ because of the use of fossil fuels required to make them. However, fired bricks and terracotta roof tiles are generally very durable. The production and transport of these building materials lead to relatively high levels of greenhouse gas emission. Alternatively, there are also locally produced and used building materials that do not create substantial CO2 emissions. This means that people should search for locally available raw materials that can be locally modified and processed as building materials for housing. Making use of the local workforce is seen as very necessary in order to provide labor and social sustainability. It is clear that each area has its own potentials and limitations. Below, attention is given to the following four groups of building materials. As stipulated, the construction aspect must always be attended well, meaning the making of adequate foundations and structures. Climate conditions can differ by region and can determine considerably the applicability of the building materials and the structures of the buildings.
- Bamboo and Timber
- Compressed Earth Blocks
- Adobe Blocks and Bricks
- Interlocking Bricks and Blocks of various materials
Bamboo and timber
Bamboo has a lot of potential as a building material for low-cost housing. In various countries in Latin America and Asia, bamboo housing is customarily a rural phenomenon, based on local production and processing of the raw materials. If bamboo housing were to also become accepted by city dwellers, there would be a need to develop vast bamboo plantations to provide the urban housing markets with bamboo for construction. Bamboo can be used in countries where it has a natural presence. One must choose the right sort of bamboo. A bamboo housing study conducted in Guayaquil, Ecuador, found that gradually after a site has been developed – e.g. by the provision of paved roads – the squatters’ bamboo houses are transformed into concrete houses. This is because the residents eventually prefer a house built with bricks because bricks have a higher ‘status’. In the past, for example the Ngo IDESAC in Guatemala has tried to cooperate with people in rural areas to stimulate house building with bamboo. But the indigenous people did want that. The families see bamboo as ‘the poor man’s construction material’, and they don’t want to be identified with that. Although so far, the use of bamboo as a construction material in urban settlements is still limited, the material is durable and is earthquake resistant if constructed well. Bamboo can be used for many purposes, such as for dividing walls, floors, ceilings, roofs, pillars, and window frames. It is also used on construction sites as scaffoldings. The use of bamboo as a major construction material in dense urban areas, however, is not to be expected. The construction of complete houses of bamboo – with a strengthening framework – is professional work (half-timbered). If it is done by self-builders, there should be guidance because of specialized carpenters. The treatment of bamboo is needed with preservatives, often being chemicals, to prevent termites to demolish the material. It must be prevented that the chemicals end up in the environment. It is recommended that the outer walls of the bamboo homes are being plastered, in order to give protection against the influences of the climate. If a full plastering of external walls of the homes is the case, the house looks like an ‘ordinary’ home. Currently, there are some interesting technological innovations concerning the construction of homes with bamboo. For example, there are strengthening corner connections and pre-fabricated wall panels that can be used for exterior walls of homes. It is to be expected that there will be more of such innovations on building homes with bamboo.
An example in Vietnam shows that the use of bamboo can be combined with other building materials. Architect Vo Trong Nghia introduced a concept of modular homes to be used in the Mekong delta area, with a lightweight steel structure combined with cheap local materials that are easy to assemble, such as corrugated polycarbonate and bamboo. Another example is in Ecuador, where the Ngo Hogar de Cristo produced many modest houses of bamboo for low-income households.
Two Photos: by Dr. Jules Janssen, Eindhoven Univerity. Middle; plastering of outer walls. Right; walls of bamboo panels (by INBAR).
Left: Bamboo corner joint. Middle: bamboo house of Hogar de Cristo, Ecuador. Right: Model house of bamboo at UNI, Universidad Nacional de Ingeneria, Managua, Nicaragua.
Hogar de Cristo has produced new housing models, nice and cheap ones, that can be built easily and rapidly, which are also cool without having air conditioning. One of the prototypes is the MACAHO model; it is a new technology that combines high strength and durability-treated wood, which supports modules consisting of concrete and cured Reed, designed so that the house can grow as the family grows. The basic module of the MACAHO house costs US$2.045. A completed house with 2 rooms, kitchen, bathroom, etc. will cost US$4,300.
Images: Information to be found at the website of Hogar de Cristo (L). Other forms of modest wooden houses (M and R). Middle: prefabricated wooden house. Right: house built of bamboo and wood (Images: Hogar de Cristo)
Using timber in house construction is comparable to using bamboo, but it is easier to handle. The use of timber in construction is customary worldwide. One must take into account transportation costs and the re-planting of trees in the area where the wood was harvested. Building wooden houses in dense urban areas is not recommended because of the danger of fires; this aspect must always be considered and controlled also in irregular areas.
Compressed Earth Blocks
Traditional building materials such as loam and adobe can be used in new ways, such as with uniform rectangular Compressed Earth Blocks (CEB) and the (Interlocking) Stabilized Soil Block (SSB or ISSB) system. In both systems, the use of cement is minimized. As a professional-grade mix preparation is necessary, a field lab and training of the labor force are required. ISSB blocks are used for the construction of buildings, latrines, septic tanks and water tanks. Appropriate earth technologies are being used, for example in Uganda, Mexico, and India. Due to their huge mass, walls made from CEB have excellent thermal performance, reducing heating and cooling costs. If constructed well, buildings made with CEB can be sustainable and durable. This implies that technological improvements can be used small-scale and at the local level, potentially contributing to local economic development. The development of Interlocking Stabilized Soil Blocks is a promising new technology which can be locally produced and applied.
Building materials facility for compressed earth bricks (CEBs) and community training center in Jinja, Uganda.
The National Slum Dwellers Federation of Uganda (NSDFU) and the Ngo ACTogeter, both working for and with the urban poor in Uganda, support a key project in the city of Jinja, concerning sustainable housing and the production of building materials. Both organizations jointly facilitate local initiatives to improve the daily living conditions of the poor in Jinja, in particular through the establishment of community savings groups. These initiatives include the establishment of a community center in Walukuba East Settlement, that aims to accommodate a variety of activities for the low-income groups living in informal neighborhoods of Jinja. It is about:
- the provision of space where local slum dwellers can meet, or live for a while;
- teaching and training facility for people who seek to improve their skills for self-help house building;
- vocational training for income generating activities.
Various workshops are also given to federation members who come from outside the city of Jinja. For the accommodation of such participants, guest rooms have been built on the two upper floors of the community center. The facility in Jinja produces sustainable building materials with which homes can be built or improved by means of self-help incremental housing (new housing or home renovations). The facility sells the building materials directly to the households, who may obtain technical assistance for a proper and professional use of the materials in self-help construction. The project provides training in construction skills to aspirant construction workers and self-building residents. Students of local technical schools can also do internships in this project and thus acquire practical skills. The center can be used for community development and as a training center. A hostel facility is included. This multipurpose community center offers possibilities to address sustainability targets concerning community building, the combat against poverty and the use of sustainable building materials. This community center is also called a ‘Self-Reliance Center (SRC)’. The aim of this SRC is to support self-reliant communities able to create incremental housing at the city level. For the operation of the SRC, community members from informal settlements need to actively participate in the programs and mobilize their collective labor toward such efforts as producing brick or cement, and participating in construction or improvement. It might well be possible for the community center in Walukuba East Settlement to perform a key role in developing a full-fledged SRC for Jinja.
Community and Training Center in 2015 (left). Model toilets made of compressed earth bricks (M) or concrete slabs (R)
Sustainability aspects of Interlocking Stabilized Soil Blocks (examples in Jinja, Uganda)
In Uganda, the walls of houses are usually built with fired bricks. This implies that clay is extracted from the soil, and that the bricks are being fired in kilns. Wood is used as fuel; which leads to deforestation and the emission of CO2 among other things. This is far from sustainable, certainly because this happens on a large scale. Moreover, the process results in uneven bricks and 20 percent waste as the bricks closest to the heat source are over-fired while those farther away are under-fired. Building walls with uneven bricks leads to excessive use of mortar.
An alternative environmentally friendly and cheaper way of building walls is through the use of Compressed Earth Blocks (CEB), put together from mining locally sand and loam, with thereby mixed a (low) rate of cement. Basically, the work can be done by local people; however, it requires a certain amount of knowledge and training. The Jinja Training and production center is performing well concerning these technologies. Several houses and toilet buildings were constructed with CEB technology, among others: the Waterborne Toilet (building) for the community in Walubuka West Market, realized with the Jinja Municipal council in conjunction with the Mukamawakisa Saving Group. There is an urgent need for funds to be able to serve a large amount of households who need a core house or home renovation in the area. One might use NSDFU funds which is called ‘Suubi and Loaning’. As the Ugandan Federation grows in size and confidence, the need for finances to support community group initiatives becomes more eminent. The Federation NSDFU, with SDI, and the Lutheran World Federation worked together to start a Ugandan Urban Poor Fund – called the Suubi Development Initiative. In the current situation, a household must have a property title or deed that must be handed over to the Federation in order to get a small loan, for example for the building of an extra bedroom, an adequate roof or a better kitchen. Besides using their own savings, households could obtain small credit and build quicker with the help of the building materials and training facility. This means that a fund for the scaling up of house construction and home renovation in Jinja is necessary. The Ngo ACTogeher is also seeking with NSDFU for new financial opportunities. All actions mentioned might lead to a new phase of their Jinja project namely a more intensive use of the existent building materials facility and community training center.
Members Saving Group in front of a toilet facility. Wall with compressed earth bricks.
Fired bricks of clay compared to compressed earth bricks (CEB)
Extraction of clay from the subsoil, and the making and drying of bricks. The kilns for the firing of the bricks (R).
The production of compressed earth blocks (CEB) with local raw materials. A house built of CEB (Right).
Technological development on CEBs, for example in Uganda
Technological development of Compressed Earth Bricks can be reached by using CEB machines in making the bricks or blocks, which brings controlled sizing of bricks and high pressure resistant. Another advantage is that bricks can be produced in bigger volumes. A CEB machine is costly and demands the use of fossil fuel, but the latter is very limited compared to fired bricks. homes with CEBs have better moisture regulation and are more comfortable than homes with hollow concrete blocks. Producers of CEB machinery mostly also offer training for the construction workers. Oskam v/f sells a mobile set of machines for the production of compressed earth blocks consisting of press, mixer, pulveriser, spraying system, screens and dosage equipment. The machine can be transported by with a 4-wheel drive. Production capacity is 360 blocks/hour, for a block size of 295 x 140 x 90mm. Employment of 8-10 persons is possible. One can produce anywhere, with a separate mobile generator (30KVA). With this machinery, several low-cost housing projects – with houses of 35 m2 – were built in the vicinity of Jinja, Uganda. In a project of around 300 homes, the costs were USD 3500 per unit. Housing was executed with the help of NGOs, and local workers and residents were trained to be a brick producer and brick layer. Load-bearing walls can be made from these compressed earth bricks, and eventually more urban housing complexes can be made of it. A thin bed of earth mortar is needed to make a strong load-bearing wall. Concrete pillars and plastering are not necessary for this type of housing in Uganda.
The Oskam v/f mobile CEB machines are used in various other countries, such as Mali and Sierra Leone, for the construction of schools and dwellings.
Oskam CEBs used for low-cost housing in Uganda and Sierra Leone (source: Oskam).
Oskam CEBs to be used for social housing project in Bamako, Mali. (design and source: LEVS Architects).
Adobe blocks and bricks
Adobe bricks are made from a mixture of clay-based soil, straw, and water. Wet adobe is formed into bricks and then laid out to dry in the sun for several days. They are used for the construction of walls, with wet adobe serving as the mortar. Methods of construction vary considerably by climate. Most homes have a coating of adobe on the outside to create a smooth surface, which can be painted. Adobe is applicable in rural areas but in urbanizing areas – with higher densities – the use of this sustainable material is not very common.
Building blocks of adobe for housing in El Salvador
El Salvador is one of the countries in Central America where the indigenous population has traditionally an extensive experience in building houses of adobe. It is material that is found and shaped in the rural areas and rural villages. Governments, aid organizations, and the mutual aid cooperative movement promote the use of adobe because it is considered to be a sustainable and durable building material, in comparison with the use of concrete, concrete blocks, and fired bricks. If the houses with blocks of adobe are being built correctly, they offer sufficient insulation and can be earthquake-resistant. Other benefits of adobe bricks are (among other things) that less cement can be used and therefore that less CO2 is emitted. Furthermore, the local and traditional construction methods in rural and isolated areas can be well-preserved and re-developed. For years, the Ngo FUNDASAL from El Salvador (Salvadorian foundation of development and minimal housing) has invested heavily in the development of adobe building blocks and corresponding construction techniques, to renew the local knowledge and promote contemporary applications of adobe for the housing practice in rural areas. It is crucial that the construction of the houses with adobe can get more respect of the local population, and that it improves the quality of the buildings and the maintenance of it, and lowers the costs of the building materials and of the whole construction. In particular, the aspect of the costs of adobe blocks for housing must be (further) investigated. It is not recommended to build houses with adobe building blocks in urban areas. When one builds with adobe as building material for housing, it should be highlighted that raw materials suitable for the making of adobe blocks are present locally in a particular rural area. The quality of the adobe blocks should be supervised and monitored, for example with regard to the dimensions of the blocks (30 by 30 by 10 cm), the making of good mixtures of raw materials, and the application of suitable construction techniques, earthquake-resistant building techniques, and proper plaster or stucco work on the walls. FUNSDASAL already has all this knowledge available and can offer instructors and trainers for building teams, and is also available to offer small mobile laboratories for experiments with soil types and mixtures (sand, clay, mud, granular, gluing, lime) in the rural areas. The qualities of plasticity and strength of the mortars are crucial. To be able to reinforce houses with adobe bricks (making them earthquake-resistant), the constructive system of adobe should be reinforced comprised of adobe walls with internal reinforcement with steel bars and/or organic elements of vertical and horizontal bracing. The finishing of the walls with stucco or plaster is important to fill the cracks, crevices, and cavities. With this, it is possible to protect the population against insects, such as the chinche picuda which is a transmitter of the ‘Mal de Chagas’ disease in some rural areas. The plaster is also necessary to protect the walls to the rain (outside) and humidity (inside). One should be able to make good mixtures of different ingredients, if possible from local raw materials. For a good execution of all what is needed regarding the manufacturing of the blocks of adobe, the construction of the houses and the finishing of the walls, professional help is desired for the empowerment of the local workers and the local population.
Photos of FUNDASALs technical research and development center in El Salvador. (1) small mobile laboratories; (2) Ing Rosa Delmy Nunez, head of Building research of FUNDASAL; (3) seismic resistant house model; (4) reinforcement system for adobe walls; (5) various types of plaster for outside walls; (6) natural color possibilities of wall plaster.
Interlocking bricks and blocks of various materials
Interlocking bricks or building blocks can be used for building walls. These bricks are available or are being developed in different shapes and sizes, for example using the principle of the well-known Lego blocks, or using comparable interlocking building systems. If an adequate sizing of these bricks can be reached, the bricks can be clicked onto each other, with only a little bit of glue or cement, or even without any mortar. If this is possible, the blocks can be reused easily in a second life. The advantage of these building blocks is that the homes can be built quickly and with a big commitment by unskilled workers, volunteers and future residents. Also, it can be used as building material for temporary houses, or emergency houses. The building blocks can have or obtain a good insulation value comparable to the common hollow concrete blocks. Moreover, interlocking bricks can be an alternative for fired bricks, and as such, they are far more sustainable. The building material can be ‘normal’ concrete in the form of hollow concrete building blocks, soil-cement blocks, concrete made of recycled materials such as bricks, and finally, recycled plastics, or recycled plastics mixed with organic materials like rice husks.
Blocks of recycled debris, in Medellin, Colombia
To help decrease unnecessary waste and pollution, construction waste and fragments of concrete can be recycled to create eco-friendly building materials for the interlocking bricks, that are dried naturally, minimizing the emissions of environmentally harmful greenhouse gasses. The use of mortar is zero and so, the amount of manual labor needed can be decreased. The use of interlocking materials reduces the amount of time needed to complete a housing construction process. A demonstration dwelling was built in Medellin during the World Urban Forum in 2014 by the municipality of Medellin. The demonstration house was promoted by ISVIMED, the Social housing and habitat institution of the municipality of Medellin, Colombia.
Photographs taken during the World Urban forum in Medellin Colombia in 2014.
Concrete building blocks Q-bricks, in Haiti
The ‘Mobile Factory ‘ is a concept being capable of changing debris into concrete building blocks that can be clicked together like Lego blocks or Q-bricks. In stacked form, houses can be built with these blocks, and one creates earthquake-resistant houses herewith. Victims of war or natural disaster, can quickly build core houses and rebuild their communities, with external technical, organizational and financial assistance. Somewhere in Amsterdam, one has built two demonstration homes. The cottages of 18 m2, and 24 m2 respectively, are prototypes of emergency housing that can be built up with the Q-bricks. The Q-bricks are produced locally in a mobile production unit or ‘mobile factory’, existing of two converted shipping containers. By the end of 2016, the Mobile Factory organization is working in Haiti in order to produce one first series of rental dwellings for a local group of families affected by the big 2010 earthquake. At the same time, a local housing cooperative is being established.
Photographs from Mobile Factory.com
Blocks of recycled plastic and rice husks in Vietnam
As basic raw materials for building blocks, two materials are used: 1) recycled plastic in the form of polypropylene, and 2) rice husks (or hulls) which is the waste of rice cultivation. The building materials can be manufactured sustainably. Rice husks are the hard protective coverings of grains of rice. After they have protected the rice during the growing season, rice husks can be put to use as a building material, insulation material, or bio-fuel. In Vietnam, the rice husks are usually burned in the open air – or just are thrown away in rivers. The materials are used to create two building materials: RHPP building blocks and roof tiles. RHPP is used to construct houses supported by a foundation and a steel framework. The materials are produced in Ho Chi Minh City by Trong Danh Co. The components of these ‘TD building materials’ are rice husks, polypropylene plastic, baking powder, catalyst, and other additives. The resulting material is resistant to fire and provides heat insulation and sound insulation. Moreover, it is waterproof and lightweight, which reduces transport costs and makes it easy to handle the materials during the construction. RHPP is produced in specially designed machines that perform all of the necessary operations, namely mixing the raw materials, heating them, mixing them again and finally pressing the end products. The results are sustainable building materials for housing (blocks and roof tiles).
Photographs were provided by Jenny Van Phan of Trong Danh. The project was executed in 2014 by Trong Danh in cooperation with AFAP, the Australian Foundation for the Peoples of Asia and the Pacific. Tey built mutually five low-cost houses and a community house in the Vinh Thanh village in the Province of Soc Trang.
Considerations at the end
Despite the advantages outlined above, city-dwellers do not want to live in houses that in their perception may consist of modest building materials. Therefore, there are probably far more opportunities for the application of the described sustainable building materials in rural areas, villages, and small towns than in dense cities. In many countries technological innovations on sustainable building materials are being developed, amongst others by private actors and by governmental or educational institutions. This is of outmost importance, and exchange of knowledge is essential. This is why UH-Habitat is interested in these matters and has executed a series of studies and pilot projects, in order to promote and stimulate the use of sustainable building materials. The goal is to cooperate with local residents in producing building materials from locally available raw materials, to be used for the construction and the betterment of their houses. Besides the goal of having produced sustainable building materials, there is the goal of training and educating local communities in house building, which leads to social sustainability.
Besides building homes with sustainable materials, the quality of the structures of the buildings determines the possibility of applicability of adobe bricks and CEBs. One must always create adequate foundations, frameworks, and roof constructions. Within the frameworks, materials such as adobe blocks and concrete or fired blocks can be applied; the frameworks itself can be of wood, concrete, steel, aluminum etc. In areas where earthquakes are to be expected, the application of frameworks is crucial. Of course, climatic conditions can also place technical demands on structures and building materials.
As UN-Habitat wants to promote sustainable building materials, they made available studies concerning these materials for housing, including assisted self-help housing, for people and communities in the countries of the Global South. In this context, a number of studies and pilot projects were carried out in different countries, amongst other things regarding CEB in Uganda (see list below).
Literature on bamboo for housing
- Livingston, M. (2009) Bamboo housing and the Mangrove of Guayaquil. Tennessee: Institute of tropical architecture, University of Tennessee.
- Gutiérrez, J. (2000) Structural Adequacy of Traditional Bamboo Housing in Latin America. National Laboratory for Materials and Structural Models, Civil Engineering Department, University of Costa Rica.
- Rodríguez, N., Dill, W., Bidegaray, P. and Botero, R. (2006). Utilización del Bambú, como una Alternativa Sostenible de Construcción de Viviendas en la Zona Atlántica de Costa Rica. In: Tierra Tropical (2006) 2 (1): 77-85.
- De Vries, S. (2002) Bamboo construction technology for housing in Bangladesh : opportunities and constraints of applying Latin American bamboo construction technologies for housing in selected rural villages of the Chittagong Hill Tracts, Bangladesh. Eindhoven, Netherlands, University of Technology.
Some UN-Habitat literature to be mentioned:
- Green Building Materials Facts Sheets on Concrete, Bamboo, Earth Materials, and Timber. Available at UN-Habitat’s website: http://unhabitat.org/green-building-materials-fact-sheet-concrete/, respectively Bamboo/, Earth materials and Timber.
- UN-Habitat, with Hannula, E. and Lalande, C. (2012). Going Green: A handbook of Sustainable Housing Practices in developing countries. Nairobi: UN-Habitat.
- UN-Habitat, with Pérez-Peña, A.M. (2009). Interlocking Stabilized Soil Blocks. Appropriate earth technologies in Uganda. Nairobi, UN-Habitat.
- UN-Habitat, with SICCMA (2011) Sustainable Building Practices for Low Cost Housing.Implications for Climate Change Mitigation and Adaptation in Developing Countries. Nairobi: UN-Habitat.
- UN-Habitat, with Butera, F. et al. (2014). Sustainable Building design for Tropical Climates.Principles and Applications for Eastern Africa. Nairobi: UN-Habitat.