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The technical solution: Nubian Vaults
The Nubian Vault (NV) is an ancient technique, standardized and adapted to meet the needs of the populations of the Sahel. After two years of technical trials, a French builder, Thomas Granier, and a Burkinabé farmer, Séri Youlou, have simplified and standardised a 3,300 year-old Egyptian building technique in Burkina Faso, Mali, and Senegal. A good example of ‘South to South’ technology transfer.
The Nubian Vault is: • an ancient technique, • using simple local materials: earth, water and rocks, • built with basic tools, • to make customtisable, comfortable and sustainable houses for all.
A SIMPLE TECHNIQUE OF EARTH ARCHITECTURE
An ancient construction technique: The Nubian Vault (NV) technique is an age-old method of timberless vault construction, originating in upper Egypt. It uses only earth bricks and earth mortar. Nubian Vaults built over 3,300 years ago at the Ramesseum Mortuary Temple, Luxor are still standing. AVN has simplified and standardized the NV technique, adapting it to the climatic conditions and traditional know-how of the Sahel region, making it easy to learn on-the-job.
Using simple local materials: The only materials that are needed to build a NV house are: rocks for foundations, earth and water for adobe bricks and mortar. The bricks are standard bricks that are made locally by the people - this does not require any special skills. Ramesseum Mortuary Temple, Luxor, Egypt 3300 Years old
With basic tools: No timber or formwork is required to build the vault, only basic tools (spade, pickaxe, trowel, wheelbarrow, spirit level) are needed, making it accessible to any mason.
A proved and affordable alternative
Since 2000, the Nubian Vault technique has proved to be a valid, ecological and affordable option, compared to the alternatives (concrete walls, metal or straw roofs), and present several advantages, making it the most promising technique for affordable housing in Africa.
A house made of earth - is it solid ? Yes, earth is a noble material with excellent resistance, thermal and acoustic properties, used by famous architects all over the world. 99,8 % of all the NV built since 2000 are still standing and in use.
Does it survive rain ? Yes, the earth roof is waterproof. In the Sahel, where all the NV are built, the rainy season is very intense and lasts 3 months. However, regular maintenance of the roof (every 2 years) is sufficient to maintain its water resistant properties.
A tested & proved alternative
BUILDING A NUBIAN VAULT
Materials required to build a standard 8m long Nubian Vault (24m2): 84 carts of earth Rocks for foundations 2,000 wall bricks 1,000 roof bricks 1 roll of local plastic sheeting 77 barrels of water
How much does a Nubian Vault house cost ? Different cost elements influence the cost of a NV which can vary depending on: - the cost of labor: depending on the country where the NV is built the average mason’s salary can vary a lot, - the cost of the materials: in certain areas, especially urban areas, the materials (rocks, earth, water) are more expensive because they need to be transported, - the participation of the clients: if the family participates a lot with unskilled manual labor, it reduces
The materials must be prepared in advance
When the team of NV masons arrives to start working, the rocks for the foundations, the water and earth for the mortar, and the bricks for the walls, must all be ready and on-site.
the cost of the house. - Formal or informal exchanges: the salary of the masons can be paid in money or on an exchange / barter basis, so the cost paid in cash can vary a lot according to the participation of the clients. All these elements influence the price of the main structure of a VN house that begins from $7-9/m2 in rural area with 70% of client participation (which represents less cash expense than building with iron roofing sheets), and can cost up to $70- 80/m2 for the highest prices in Senegal in urban areas without any manual labor participation of the client which is on average 50 % cheaper than the same type of constructions in concrete.
NB: the types of finishes vary a lot depending on the client’s needs, taste and means but are not included in these costs.
Let’s take two exemples:
1/ A NV house of 25 m2 in Burkina Faso, where the family provides the unskilled manual labor and the mud bricks (the case for 70 % of our target popuation), the house costs about $175 to pay the skilled NV masons, and to cover costs of basic finishes.
2/A NV house of 50m2 in Senegal for a family in an urban area unable or unwilling to contribute unskilled labor for construction, the house would cost around $3,000, to cover all skilled and unskilled labor, and the transport of materials to the site.
1 Choosing a site It is essential to choose a site that is not in danger of seasonal flooding. It’s also a good idea, especially on plots of limited size, to plan ahead for future extension of the house, or the addition of an extra storey.
2 Digging the foundations Foundations can vary from 40 to 80 cm deep; they need to be 70 cm wide for load-bearing walls, and around 50 cm wide for the gable walls. They are filled with rocks, bound with an ordinary earth mortar.
3 Making the Bricks Two types of bricks need to be made: > the large bricks for the walls: standard bricks that people are used to making. > the roof bricks: they are smaller and are made of very good quality earth by the NV masons.
4 Building the walls
Walls are of standard thickness of 60cm, and openings for doors and windows are a standard size.
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Building the Vault
The roof is exclusively vaulted (no domes) and of a standard width (3,25 metres). It is built without formwork, but with a guide cable to define the curvature of the vault.
7 Waterproofing the house
Locally produced plastic sheeting is incorporated in the roof to reduce water penetration and erosion. Gutters are also installed to drain the rain.
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Finishes
The inside and outside walls are covered with mortar, cement or laterite bricks and can be decorated according to the client’s taste and resources.
The Guide cable is used to define the curvature of the vault, avoiding the need for formwork.
Gutter
Plastic sheeting, locally produced
Interior personalisation by the clients
Various levels of customisation Customisation of NV buildings over time:
Double storey House
The NV technique allows for later extension of a building, by lengthening a vault, by adding further vaults on the side of an existing one, or by adding a second storey onto an existing single storey building (on condition that this was foreseen when the foundations were laid). It is easy to re-arrange the interiors of a VN building (e.g the adding or removal of internal partitions, the opening or closing of doorways, and window and alcove arches).
This modular potential increases the popularity of VN architecture, as homes can be ’grown’ to match developing family needs. NV technique with reinforced concrete Although there is no limit to the length of a NV vault, its width cannot exceed 3.25 metres. As some buildings (e.g. classrooms, religious buildings, community centres...) need to be much wider internally, we have developed a technique combining NV vaults with reinforced concrete beams and pillars (NV+RC) to support the vaults. With various technical partners, some 30 buildings have been constructed using this combination, in Burkina Faso and in Mali.
NV + Reinforced Concrete beams and pillars
Long term external Finishes The use of a mix of tar/sand/earth/lime for the external finishes or the use of laterite bricks or concrete blocks for the outer layer of load-bearing walls gives a very attractive finishing coat and avoids the need for re-rendering. finishes in tar/sand/earth/lime
A POLYVALENT ARCHITECTURE
The Nubian Vault technique allows for the construction of various types of buildings, from basic rural houses to urban mansions, from agricultural barns to schools or public buildings. Office
Roof terrace
Religious or public buildings
Rural houses
Agricultural barns
Urban mansions
WITH SEVERAL ADVANTAGES Affordable
Houses using the NV technique can cost half the price of those built with brick or concrete block walls and roofs of sheet metal on timber rafters, making it affordable for families with small budgets.
Durable
A properly maintained NV house can last 50 years or more, compared to the average 10 year lifetime of one with thin concrete block walls and sheet metal roofs.
Modular and polyvalent
Standard vaults of 23m2 (7m X 3,25 m) can be used for a wide range of buildings (houses, schools, health centers.. ), of different styles (terrace roofs, twostorey buildings, courtyard buildings...), which are easily extendible. A NV house can be ‘grown’ to adapt to the needs of an expanding family.
Solid and fireproof Ecological and sustainable
A NV house only uses locally available raw materials: no metal sheets, no timber beams or rafters. So it has a very low carbon footprint, as none of the building materials need to be manufactured or transported long distances, nor do any trees need to be cut down. > no wood: 1 NV* saves 4 trees > no sheet metal, cement or steel 1 NV saves 2 tons of CO2-equivalent. *A standard NV equates to ~ 25 M2 of floor space
Comfortable
Provides excellent thermal and acoustic insulation (cool during the day and comfortable at night), and avoids the infestation by vermin and insects common in straw and timber roofs.
Thick walls and weather resistant roofs provide solid and fireproof houses compared to traditional thatched roof huts, which can easily catch fire.
Saves local culture & aesthetics Infinitely more attractive than tinroofed houses, it incorporates traditional practices and aesthetics of earth architecture such as a flat roof terrace.
Flat roof terrace
Creates jobs and local economies
The NV program is based on the rapid training of apprentices and on the use of local materials. Thus, it creates jobs and stimulates local markets and economies.
Client M. Larou Lontié, a farmer and the first client of the AVN pilot village program in Poundou says: ‘My house is solid – everyone knows that. I made the calculations myself, and it’s clear that the NV technique is less expensive than tin roofing. In my village, lots of people helped me – men collected rocks, made the bricks, and helped me with labor, and the women brought the water.’
An affordable house for all Thanks to flexible payment arrangements, from self-build to cash. The NV concept is well adapted to local socioeconomic conditions. It has always been the case in rural and poor urban areas that many house-building tasks, especially those involving unskilled labour, are carried out by the clients, their families and neighbors. The vast majority of VN masons’ clients in our priority target group (rural and periurban families) contribute unskilled labour in building their houses (digging foundations, carrying materials, making mud bricks for the walls ...). The proportion of this ‘self-build’ contribution varies from client to client, and from one building site to another. However, the work of the skilled NV master mason and his team (about 25-30% of the cost of the main structure) is almost invariably paid for in cash Some wealthier NV clients do pay for the entire construction (unskilled and skilled labour, purchase and transport of bricks) in cash, but they are in a minority.