ABSTRACT
Rock can be immensely strong, as witnessed by many natural arches seen along coastlines and occasionally inland (Fig. 2.1). At times its inherent strength has been utilised in situ (e.g. the rock hewn buildings at Petra, Jordan, or the monolithic churches at Lalibela, Ethiopia (Fig. 2.2)) and is regularly relied on in tunnelling and in forming underground chambers. However, normally, it is required to be cut into blocks in order to be transported from quarry to site, in which case the structural performance of the finished building tends to be dominated by the way the blocks are shaped and put together, rather than by the strength of the original material. A strict definition of masonry would only include those structures built of stone dressed and placed by masons. However in this chapter, a broader definition is used involving also structures built from undressed stone and what might be called artificial stone, comprising bricks, tiles or concrete blocks.
