The last alternative building method I want to touch on is rammed earth construction. According to Dictionary of Architecture and Construction, 1975, rammed earth is “a material usually consisting of clay, sand, or other aggregate (such as sea shells) and water, which has been compressed and dried; used in building construction.” This is a building method that has been around for thousands of years and some great examples are the Great Wall of China and the Alhambra in Spain.
These buildings are environmentally friendly and water, fire and termite resistant. The cost of these buildings is more than that of conventional buildings, because it is a labour intensive method. It differs from cob buildings, because here the mixture is compacted into forms and later, when the forms are removed, the solid earth walls remain, as shown in Figure 1. Modern day methods include up to 10% cement and some steel reinforcing in areas where earthquakes occur.
This is a construction method where skill is required and because the earth is compacted into forms, the freeform shapes of cob are not achievable. These building have a more conventional look in shape and form, but can stand out aesthetically from other buildings where conventional building methods are used, if you play around with the height and colour of the different layers.
Figures 2 and 3 are from an article posted on FineHomebuilding showing a house built with rammed earth where all the layers are more or less the same colour. (https://www.finehomebuilding.com/2019/03/13/rammed-earth-construction)
Figures 4 and 5 below are examples of what can be achieved when playing around with the heights and colours of the different rammed earth layers. Figure 4 is an extreme example of a rammed earth wall built in Ghana and Figure 5 is a photo taken by Nic Lehoux of the Nk’mip Desert Cultural Centre, Osoyoos, Canada.