Zambezi River House, Livingstone (ZRH)

ZRH was built using a novel construction method called Rammed Earth Technology. Rammed earth walls are constructed by ramming a mixture of selected aggregates, including gravel, sand, silt, and clay, into place between flat panels called formwork. In this case, these aggregates are mixed with cement to create a stabilised rammed earth, a variant of traditional rammed earth, to increase strength and durability. Stabilised rammed earth walls need little added protection but are usually coated with an air-permeable sealer to increase the life of the material.

The colour of rammed earth walls is determined by the earth and aggregate used. It is also possible to add powdered colour, such as red or grey oxide. The ramming process proceeds layer by layer and can introduce the appearance of horizontal stratification to the walls. Stratification can be controlled as a feature or eliminated.

Aggregates can be exposed, and special effects created by the addition of different coloured material in some layers, and elements such as feature stones or objects, alcoves or relief mouldings can be incorporated into rammed earth walls. Decorative finishes can be achieved by including shapes in the formwork that can be released after the wall has been rammed.

Rammed earth is very strong in compression and can be used for multistorey loadbearing construction. Research indicates that monolithic earth walls perform better under earthquake conditions than walls made of separate bricks or blocks. Rammed earth can be engineered to achieve reasonably high strengths and be reinforced in a similar manner to concrete. Horizontal reinforcement is not recommended and excessive vertical reinforcement can cause cracking problems.

Rammed earth behaves as heavyweight masonry with a high thermal mass. Thermal mass absorbs or ‘slows down’ the passage of heat through a material and then releases that heat when the surrounding ambient temperature goes down.

Used correctly, and in the right climate, the thermal mass of rammed earth can delay heat flow through the building envelope by as much as 10 to 12 hours and can even out daily temperature variations. Rammed earth walls become effective when the difference between day and night outdoor temperatures is at least 6°C.

Total Project Cost: 2,300,000