The green building movement has resulted in the experimentation with alternative, more sustainable building methods, most of which have been around for hundreds of years.
As architects and designers we are always up for a challenge and willing to try new things. In 2007 we were approached to design a permanent structure on a site in Mamelodi where a tent was used as a Community Centre, with the main purpose being that of a day care for the kids of the local community. Because of budget constraints, we proposed using a timber pole and sandbag construction method which can be done by local and or unskilled labour. Besides the fact that this is a cheaper way to build, it is also environmentally friendly and sustainable. The walls were constructed by stacking sand bags between timber poles and corrugated iron roof sheeting on treated timber pole rafters were used to construct the roof. In this case we opted to leave the sand bags exposed on the outside and to plaster the walls on the inside, but you can plaster the outside walls as well for a more conventional look. Unfortunately the local council was not willing to approve the alternative building method at the time, which means the buildings were never built.
The benefits of this construction method:
Local site sourced fill material can be used to fill the bags, which dramatically reduces fossil fuel use and transport costs to site. The only water usage is in the concrete floor and foundations and the plaster finish on the inside of the walls. These sandbags have excellent thermal insulation and will drastically reduce the heating and cooling costs over the life of the building. The construction process can easily be learnt by an unskilled person in just a few days, therefor the local community can be involved. The construction time is also faster than conventional brick and mortar. All the above results in a reduced construction cost. Figures 3 and 4 are of a fully plastered house built from sandbags by Cygnet Property Limited, and Figure 5 is an internal wall done by Eco Design Architects, which is removable and low cost.