Customisation of NV buildings over time
The VN technique lends itself well to various levels of customisation:
- it can be adapted to suit the needs and financial resources of a wide range of clients, from the poorest rural families to wealthier urban ones
- it 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 VN buildings`(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, as illustrated in the slide show below:
Some NV buildings even have structures over two storeys in height - examples include a church tower, and several mosque minarets.
The range and variety of popular adaptations of the NV technique demonstrates the richness of the concept. Churches, mosques, school classrooms, dispensaries, agricultural buildings, verandahs, two-storey houses etc. are enriching the range of applications, and are firmly based on the original simplicity, modularity, and strength of the concept. The only fixed constraint is the maximum internal width of a standard vault, which - for reasons linked to the large-scale deployment of the technique - must not exceed 3,25 metres.
NV technique + 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, churches, 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.
The combination of NV vaulted roofs with reinforced concrete pillars and beams provides much wider open spaces (7 to > 10 metres); it also has other advantages:
- a saving of 25% in overall costs compared to comparable metal roof buildings
- a major involvement of local people (= eventual users), as unskilled labour
- a re-injection of building costs into the local economy (labour)
- a reduction in the purchase of imported materials
- enhanced sustainability and comfort of the building.
With various technical partners, some 30 buildings have been constructed using this combination, in Burkina Faso and in Mali. AVN can recommend masons or building firms with the necessary experience.
Flexible payment arrangements: from self-build to cash
The NV concept is well adapted to local socio-economic 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 neighbours.
The vast majority of VN masons' clients in our priority target group (village and peri-urban 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 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.