A thousand hills and a million stones. What next?

This newspaper recently published an article calling on us to lean towards ecological architecture for greater success in sustainable development. This further inspired the author to take a closer look on prospective cases within the City of Kigali, if you like on a paparazzi style. I must admit that it had been a while since I drove around Gisimenti in Remera. Did someone notice the new cobblestone roads there? Rwanda is indeed already looking a little bit more keenly and borrowing a lot faster from native builders and the increasing use of natural stone on buildings and cobblestone roads is a good proof for this. For Rwanda, the nickname the land of a thousand hills literally means that she is sitting on huge reserves of stone; a building material which is sustainable, highly durable, low maintenance, with high thermal mass, which comes in many shapes, sizes, colours and textures and that which blends very well with the natural landscape. Just to throw in some knowledge on stones from primary school science lessons, stones for buildings or roads are derived from one of three naturally occurring rock types: Igneous - Hard and non-porous rock formed from the slow or quick cooling of molten magma. The best example is granite. Sedimentary - Soft and fairly porous rock formed from deposits of eroded pre-existing rock that settled in layers mostly on sea beds, and became compacted. The best examples are sandstone and limestone. The third is Metamorphic - Hard and non-porous rock formed from pre-existing rock that has been altered by intense heat or pressure. The best examples are marble and slate. The applications of these various types of stone in construction industry can be summarised into; building foundations, buildings walls, rendering facades, laying on floors and roofs and landscape features, to mention but the main ones. Where as granite, sandstone and limestone can all be used for building walls, slate that comes in thin slices is only suitable for roofs and floors as it would be hazardous on vertical surfaces in case of spalling and falling off. In the Northern Province, following decades of historic volcanism, we have huge reserves of volcanic rocks. Over the years, the local population in Musanze has wisely tried it on their homes especially the boundary and garden fences using the ‘dry stone stacking’ technique in which irregular shaped stones are piled vertically to form freestanding structures. Such structures are very cheap to put up as stone is locally collected and the implementation needs minimum skills, no motor (cement or lime mixture pasted) is used between the stones - instead the weight of the some on top pushes inwards to support the structure and any slight setting strengthens the joint further. It was not until 2011 when MASS design group, a leading USA-Rwandan based architectural firm, explored the utilisation of volcanic stone as a cladding material on one of their project in Rwanda- Butaro Hospital in Burera District. The project has made headlines and won awards globally for its sustainability and has ever since provided a satisfactory precedent for academia and practice on sustainable construction in Rwanda. For instance, it was a great inspiration for the University of Rwanda’s College of Science and Technology library located on Camp Kigali, Nyarugenge campus, among other projects. Likewise, it was not until 2012 that Rwanda started producing granite tiles locally cutting largely on the import of the same. The debate of rapid urbanisation in the EAC region which unfortunately heavily relies on imports of the vital construction material has attracted the attention of government and academia. However, not all is lost. In Rwanda, stone is consistently and heavily used for foundations and retaining walls. In fact a big percentage of all medium construction projects such as residential houses sit on stone foundations. Stone masonry is another promising technology where stone blocks are laid in rows of even or uneven sizes and heights and fixed in place with mortar to construct walls that do not need extra plaster or render. This has been applied largely for many urban projects in neighbouring countries such as Kenya. What we need to do next is continue experimenting more and more the use of stone building applications; for example at the architectural scale, stone can be sustainably used for floors, walls, arches, roofs, furniture etc. while at the urban scale, we have roads, pavements, walkways, landscape features etc. It is undeniable that stone exists in huge reserves and can easily be recycled for other building purposes. The benefits of stone are straightforward and undeniable. For a country like Rwanda, good construction stone will be found locally or at few kilometres distance and usually cheap, if not free. Stone requires minimum skill; in fact some techniques such as the ‘dry stone stacking’, placing river stones on the garden, etc. require no skill at all. This make is pretty much easier to build structures, construct roads, and create beauty with stone that other construction materials. Again, stone is durable; it is fireproof, and won’t be attacked by termites, does not rust or rot. This make is maintenance free. Further, stone is attractive and blends well with the natural landscape; it can be cut into shapes, sizes, colours, and textures to suit the client, and at the same save time, money and labour. In terms on climatic comfort, stone is a good insulator so with the global debate on energy efficiency, it can come in handy; there exists scientific proof that stone will absorb excess heat during the day and radiate it back to the space in the evening to warm the cold interiors. Lets join hands to promote the ‘Made in Rwanda’ campaign in every possible way. We need to build with stone again and again, more and more. The writer is a lecturer at the school of Architecture, University of Rwanda. She is an architect and urban designer with keen interest on the dialectical relations between Architecture and Society.

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A thousand hills and a million stones. What next?