Sustainable shells: New African vaults built with soil-cement tiles

Abstract

The Mapungubwe National Park Interpretive Centre, South Africa achieves economy of means, social improvement and low environmental impact in a remote World Heritage site. This paper outlines the design methodology and construction process for a series of thin shell domes and vaults in rural South Africa. We use the Valencian tradition of tile vaulting, a 700-year-old construction system, to create lightweight and durable buildings from thin soil-cement bricks. The load-bearing masonry is used to construct roof vaults achieving high structural strength with minimal material. The largest free-form vaults span 14.5m with an unreinforced masonry vault of 300mm thickness. We replaced fired-clay bricks with less energy-intensive stabilized earth tiles, which have a well-established tradition in sustainable practice. At Mapungubwe they are used to create sophisticated engineered forms by adapting a hand-press to locally manufacture tiles of sufficient strength. In addition to being structurally efficient, elegantly simple and environmentally sustainable, tile vaults have advantages for construction in developing areas. When compared to conventional construction, this system offers material and financial savings, waste reduction, and local employment with transferable outputs and skills for future projects. For this project, we introduced the structural masonry of tile vaults to South Africa, and for the first time we combined tile vaulting with locally made stabilized earth tiles that have low embodied energy. No steel reinforcing simplifies construction, lowers cost and reduces embodied energy. The vaults are built with minimal support, saving time, money and resources on formwork. The Centre represents a significant step forward in structure and material for sustainable construction.