A sheltering roof
The consideration of the climate and its characteristics is the starting point of our reflections. During the dry season, it is necessary to create shade in order to protect against aggressive solar radiation, while during the monsoon, it must be shelter from diluvian rains and increase cross-ventilation to reduce the humidity of air. The roof quickly appeared as the essence of our concept. A roof to protect. A roof to gather.
One shelter - multiple spaces
The shelter is a protective element for users and material faced with diverse climatic situations. Indeed raw earth is very sensitive to water. It needs “good boots”, the base, and a “hat”, the roof, to isolate it from infiltrations and capillary actions which could damage it. The roofing work above these walls is essential for long term protection. Nevertheless, we have extended the reflection to the building construction stage. The latter can sustain various meteorological risks, run slow, and the earth work can be damaged. Rather than adopting a classic proceeding of the construction, by the foundations of the walls, it lifting, then framework and covering, we decided to reverse the process by starting with the roof, insuring work durability during construction work. This choice can also serve to builder comfort. Whether during dry or wet season, the builder are sheltered from the sun or rains.
Once the roof is built, the possibilities of appropriation are various. The sheltered space can remain open and serve as gathering or performance place for the community, as workshops, or simply as a covered space under which we shelter to relax, study or eat. Walls can be erected to define new spaces: a classroom for traditional lessons, a workshop for manual practices. It adapts to the community needs. It is also possible to think of more private spaces under this roof, as such dormitories or sanitary facilities.
Revealing local culture
The aim the project is the design of units for a vocational school designed to teach local arts and crafts. It seems essential to us that our proposal becomes driving force of this education. On one hand, with the use of raw earth encouraged by Nka Foundation, it is a matter to reveal the advantages of this resource to the local inhabitants in order to encourage them to maintain their vernacular culture.
The proposed building endeavours to use several constructive techniques (rammed earth, cob, etc.) in order to strengthen this process. More foreign techniques are used in order to enrich the community’s constructive culture.
On the other hand, we looked at African primitive Arts. The latter, although being very different from one tribe to another, is geometry by essence. Forms combine, multiply, differ by their contrast, and have been a real source of inspiration to us.
Building a roof
As we previously presented, the essence of the project lies in the covering. The roof shelters the earth, protects the users, and gathers them in a same place. The process which brought the design to life was fuelled by simultaneous thoughts, enriching each other. We conceived it on a structural, economical, practical and finally aestethic point of view.
Our first sketches took on the project as a “teepee”. The sloping roof favours the runoff of rain, but presents too much windage, it is cut at the top. In order to increase the slope for the water runoff, the roof is broken. This approach allows the enlargment of the interior volume, the improvement of structural performances, as well as the reduction of the construction cost. Little by little the structure is divided in shorter sections, which implies the use of smaller wood pieces, and therefore less expense. In order to restore habitability to the space, openings are created in facades to bring air and light.
At this stage of reflection, structural questions are mixed up with ascetically questions. We wanted African primitive art to be revealed by the building form itself. A tapestry serves us as a reference, it regularly composes triangular shapes, playing on contrast and a rich colour palette. That is how we introduced the triangulation idea to create the structural units. This principle contributes to the aesthetic aspect on one hand, and to the structural effort on the other hand.
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In order to question ourselves on the structure and the feasibility of our reflections, we worked with models at different scales. This allowed us to define the measurements, the ranges, the connections, and the overall stability of the structure.
Further to structural and economical issues, we rolled out our research to the nature of the covering. This one is composed by stretched canvases, which adjusts themselves like skin to the skeleton growths they cover. The project’s essence is to be able to be protect from solar radiation and rainfall, it seemed interesting to us to propose different protection systems. On one hand, permeable canvases sets up on some sides of the structure in order to shelter from the sun. It shades the spaces and allows large openings for cross-ventilation. These canvases are fabrics which may serve as media for the student pictorial art.
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Rainy season going on a shorter time, waterproof canvases can be roll out to protect the users from bad weather. A gutter and canal system is developed in order to salvage rainwater, which is stored into appropriate tanks.
Adaptable and scalable spaces
As we presented previously, the possibilities of organisation under this shelter are multiple. We have thought more in detail the pedagogic units which are classrooms, approaching the spatiality and materiality questions.
The base quickly appeared as an essential element of the reflection. Necessary to avoid capillary actions in the earth walls, it became a tool for the spaces design. The ground is raised by fifty centimetres using peripheral continuous foundations which define the perimeter of the construction. The ground cover consists in tamped earth, a traditional technique in African architecture. The rammed earth walls can be erect on the continuous foundations. In this way, it is isolate from the ground and water flows.
Under the roof, the base is knocked out of its alignment in order to orientate spaces and create an entrance system. By a shift play, a veranda marks a buffer space between interior and exterior of the classroom.
We not only thought about arts and crafts teaching in an academic way within the usual classroom environment , but also in a practical form with multipurpose spaces which could receive workshops. Thus, we don’t propose the construction of a single class unit, but two. The latter are defined by massive earth blocks which shelter secured storage spaces, but also water tanks. Between these two volumes, the space is opened and classes can be joined. Sliding wood panels allow this connection, as the opening towards the veranda.
The project’s design has been developed according to two main axes. First, the use of raw earth in construction is an ancestral technic in Africa. However, in many developing countries, we can observe that populations turn to “Western” materials. Concrete, breeze blocks, corrugated zinc, etc., are synonymous with wealth for them. Besides a highest cost and an unsuitability of the local context, these materials don’t follow the philosophy of sustainable development, because they originate from nonrenewable resources. Earth, meanwhile, doesn’t represent any cost, since we use the site soil. Moreover, it has strong thermal, hygrometric, and healthy qualities. The initiative of the Nka Foundation is a way to improve the image of this resource in the eyes of the local population.
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Secondly, our reflection focused on the complicated climate context, and the answers we could supply in order to provide comfort to the users. Tropical dry climates present characteristics which put humans in an uncomfortable situation: high temperatures, solar exposure, air humidity, rainfall, etc. It’s important to propose an infrastructure which allows the creation of an appropriate and comfortable space throughout seasons.
A sheltering Roof - Competition board submitted to Reinventing the African Mud House - 2017.