Logement Populaire Sahélien

Location:
Mauritania
Type of use:
Housing
Year of construction:
2022-2023
Size:
280 m²
Architect:
Al-Mizan - Architecture et développement au Sahel

Necessity

The Sahelian region of Africa is currently facing a number of interconnected challenges. Among them are the effects of climate change, which manifest in increasing aridity, reduced and irregular rainfall, flooding, and significant temperature fluctuations. At the same time, ecosystems in the region are becoming increasingly fragile due to recurrent droughts and human activities, particularly logging. These pressures also contribute to the degradation of traditional habitats: wood resources that were traditionally used for roofing are disappearing, while industrial building materials often prove unsuitable for the local climatic conditions.

In addition, strong population growth, rapid urbanisation, persistent poverty, and weakened ecosystems are contributing to widespread precarious housing conditions. In sub-Saharan Africa, it is estimated that around 200 million people live in precarious housing (UN-Habitat). For all these reasons, promoting new models of sustainable housing adapted to the Sahel has become a key contemporary challenge. The project seeks to address this issue, in its own modest way, by contributing to the development of such approaches.

Affordability

The use of the Nubian Vault technical concept, and therefore of adobe as the principal building material, contributes to the promotion, revitalisation, and strengthening of local industries and skills in the region. Owing to its potential for artisanal production without the need for machinery or hydraulic binders such as cement, adobe is a quintessential local building material and one that is particularly well suited to the Sahelian context.

In addition, this technique enables the client or beneficiary to participate directly in the construction project in the form of unskilled labour, such as the supply of local materials or labour input on site. This particular characteristic often leads to highly competitive costs for the Sahelian version of the Nubian Vault technical concept, which competing construction methods are frequently unable to match.

Simplicity and Appropriateness

Taking into account the defining characteristics of the local context, including the climate and the availability of resources, the architectural approach is founded on the Nubian Vault technical concept, which has been promoted across the Sahel by the Nubian Vault Association. This construction solution is particularly well adapted to Sahelian conditions and is based on the use of raw earth in the form of load-bearing adobe walls, which support vaulted adobe roofs constructed without formwork.

The load-bearing walls, with a thickness of 40 and 60 cm, together with the vaults, which measure a minimum of 32 cm at their thinnest point, give the building envelope a high degree of thermal inertia. Adobe further contributes to effective humidity regulation, while natural ventilation ensures constant air circulation throughout the building. These design principles support user comfort while maintaining minimal technological dependence

Sufficiency and Efficiency

The project demonstrates strong economic competitiveness, with construction costs at least 13% lower than those of an equivalent all-cement model. In addition, it generates significantly greater local economic benefits, at least 80% more than the comparable cement-based alternative, by relying more heavily on local resources and labor.

Another key advantage lies in the reduced consumption of high-carbon materials. Compared to an equivalent all-cement model, cement use can be reduced by 60 to 100%, while iron consumption can be lowered by 80 to 100%. The project also relies on clean, short supply chains: the construction soil is sourced within a 10-kilometre radius, sometimes directly from the construction site itself using excavated soil. Adobe bricks are produced on site without the use of machines, firing, or hydraulic binders. At the end of the buildings’ life cycle, the materials can be fully reintegrated into the environment, making the structures 100% recyclable.

Scalability

The Nubian Vault technical concept is rooted in traditional local materials such as adobe and in construction techniques, particularly load-bearing walls, that are widely found across the Sahelian belt. Within the framework of this project, the use of this construction system also makes it possible to engage with an emerging sub-regional sector, notably through a network of dynamic actors, while further strengthening a specialised local workforce whose training began in Mauritania in 2016 through a range of projects.

The pilot demonstration projects implemented in 2022 and 2023 were conceived as training sites and involved Burkinabe master mason trainers specialised in the Nubian Vault technical concept, together with local apprentices from both host and refugee communities. In total, fourteen local apprentices were trained in the earthworks phases of the sites.

Beauty

Architectural styles throughout the Sahelian belt are highly diverse, yet they frequently share a number of common characteristics, including the use of raw earth in the form of adobe, load-bearing walls, and flat roofs with a slight slope. These features form part of regional architectural cultures and are reflected in the project. The principal innovation lies in the integration of a Nubian vault, which offers a response to the roofing challenge posed by the scarcity of timber and the inadequacy of industrial materials, while retaining the possibility of a roof terrace through the use of a loaded vault.

Two further design principles are also of particular importance. The first is modularity, which enables the dwelling to be extended progressively in accordance with the users’ means and needs. The second is modernity, which challenges the often outdated image associated with adobe and repositions it as an appealing and contemporary material.

Unique Principles of Success

1. Modular and scalable design

The project is based on a sustainable, modular and scalable affordable housing model using the Nubian Vault technical concept. All housing types derive from the same 20 m² "simple module”, which can be combined in different ways to create various layouts depending on needs. The system also follows a logic of gradual expansion, allowing buildings to grow over time according to the users’ needs and financial means.

2. Affordability and adaptable levels of finish

To make the housing accessible to different income groups, the project offers three levels of finishing economy, basic and comfort, allowing customers to choose according to their budget while relying on the same structural module.

3. Inclusive and open-source approach

The term “popular housing” was preferred to “social housing” in order to emphasize the inclusive character of the project and its open-source approach. The aim is to enable Sahelian populations to appropriate the model as independently as possible and to encourage its free use and dissemination.

4. Compatibility with local construction dynamics

The project is designed to function in different implementation contexts. One possible outlet is organized construction carried out by landlords or other operators, while another is a more autonomous popular market, similar to most housing construction in the Sahel, where households build progressively through informal channels.

Limitations

The “Sahelian Popular Housing” project forms part of a sub-regional effort to develop the market for the Nubian Vault construction technique, a process that began 25 years ago. This dynamic involves a wide range of stakeholders, including the Nubian Vault Association, civil society organisations, technical and financial partners, ministries, and local authorities, and is supported by substantial long-term efforts in advocacy, deployment programmes, and vocational training. The main challenge is to achieve large-scale adoption of the technique so that it can make a significant contribution to transforming construction practices in the region, improving the living conditions of vulnerable populations, and reducing the negative environmental impact of the construction sector.

At the level of the territories concerned, however, the results achieved over 25 years of production, including more than 7,000 construction sites in six countries, 1,000 active workers, 180,000 tons of CO2 saved, and €6.3 million generated locally, still remain marginal in comparison with the considerable volumes produced by the construction sector as a whole across all techniques over the same period. Moreover, several obstacles continue to slow this momentum and hinder the desired scaling-up. These include the high level of risk perceived by households in the housing sector, especially when it comes to new techniques that are still little known or insufficiently recognised; negative preconceptions about raw earth materials, which are often seen as outdated, fragile, or requiring overly frequent maintenance; the reluctance and limited vision of some political decision-makers; the fragility of the current development model, particularly the difficulty of securing funding for long-term programmes; the influence of the cement lobby; the difficulty of standardising the technique, as local standardisation bodies are generally familiar only with concrete; and the need for change within the vocational training sector. Each of these obstacles represents a challenge that still needs to be overcome.

Logement Populaire Sahélien

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