Earthly powers: building with earth-based materials was one of the very first human pursuits, but like all materials, the architectural evolution of stone, brick and concrete continues to be shaped by changing technological, economic and social factors, which now include pressing issues of sustainability.

Building with earth-based materials such as stone, brick and concrete dates back to the beginning of human civilization. Prehistoric tribes experimented with the first sun-dried bricks or adobe, mixing mud with straw into manageable building blocks. Kiln-fired bricks were invented by the Mesopotamians to create the complex towering ziggurats of the Sumerian and Babylonian empires. Drawing on huge geological riches (limestone, sandstone, alabaster, granite and porphyry), the Ancient Egyptians were the first to use stone, building temples and pyramids on a scale that still astounds. But such epic feats could not be achieved without a cast of thousands of slave labourers. (As Richard Weston notes in his perceptive study of the relationship between materials and form, working in the quarries or being 'sent to the granite' was considered an especially severe punishment for criminals.) (1) The pyramids' limestone and granite casings were subsequently stripped to build Muslim Cairo.

The Romans invented concrete, mixed from pozzolana, a volcanic ash mined on the slopes of Mount Vesuvius, which forms a natural cement when combined with lime. Lightweight aggregates such as pumice stone were also added to the mix, giving concrete its name derived from the Latin concretus, meaning grown together or compounded. The soaring coffered dome of the Pantheon and concrete vaults of the Baths of Caracalla were early examples of the material's potential, though early experiments with bronze reinforcing bars were not a success.

Despite Roman ingenuity, concrete was to remain largely unexploited until Joseph Aspdin took out a patent for Portland Cement in 1824. Brick and stone, by contrast, were extensively used up to the modern era. The craft of brickmaking spread throughout Europe on the coat tails of Rome's legions, flourishing wherever there were suitable deposits of clay. The 'modern' short, thick brick arrived in northern Europe in the mid twelfth century, replacing the long thin Roman original, and was widely used in northern Europe, particularly in Germany and the Netherlands. Dutch enthusiasm for the new material was particularly keen and by the seventeenth century, one kiln could produce over half a million bricks in a single firing. Dutch brick went round the world as ballast in trading ships, confounding its origins as a local, geologically dependent material.

In terms of manageability, brick has always had the advantage over stone, but lacked the ennobling attributes that only stone could confer on a building. Even today, a veneer of clip-on stone is (misguidedly) thought to redeem the most unprepossessing speculator's shell and core (a practice with which the Romans would have been familiar, as they used a thin revetment of stone to dignify notable structures). The relationship between architecture and stone was more crucially dependent on geology, the availability of a particular stone literally making manifest the spirit of place. The triumph of the Florentine Renaissance depended on easy access to large quantities of pietra serena in the surrounding hills, a magical, malleable stone that gave shape to new forms and ideals. Georgian cities such as Bath and Edinburgh derived their harmonious, homogeneous character from the employment of local stone.

Anything goes

Before the present era of global industrialization, limitations of transport, labour and most especially technology ensured the continuity of a vernacular architecture based on local materials used within a limited technological framework. Now both the knowledge and the will exist to transcend or simply ignore the innate properties of a particular material. Metal is deformed in increasingly convoluted ways, glass is used in compression, stone exploited in tension. In some ways, the historical arguments about the nature of materials that have animated architectural debate from Semper to the Modernists have become irrelevant as technology makes anything possible; but in most cases, this has only served to have a generally impoverishing effect on the built result. As David Dernie observes in a new book about the relationship between architecture and stone: 'Design, in its full sense, was traditionally a process that moved between ideas and their embodiment in the fabric of the building. The richness of this creative discipline has been eroded to become a process now characterized by incoherence: material effects, fashionable surfaces are all too often used in place of deeper and more imaginative explorations of material'. (2)

Though earth-based materials still tend to be overshadowed by their racier, lighter counterparts, certain architects are capable of engaging with them in imaginative ways. Rejecting the insubstantial world of digital figmentation, Tadao Ando's poetic explorations of concrete as mass tempered by light and Peter Zumthor's handling of stone in his Thermal Baths at Vals (AR August 1997) manifest a deep understanding of the nature and language of materials. The established generation of Iberian architects such as Moneo and Siza has always made highly creative use of masonry, but they are now being joined by younger designers such as Mansilla and Tunon, Eduardo Souto de Moura and Churtichaga and Quadra-Salcedo, whose new library is featured in this issue (p22). We also look at the way in which Zaha Hadid (always more interesting when actually building something) uses concrete to physically realize the gravity defying forms of her architectural imagination (p54).

Encouraging sustainability

Any discussions of the nature of materials must now also encompass the often challenging issue of sustainability. The earth's geology is not infinite; unlike timber, stone and brick are not derived from sustainable sources. Quarrying is an inherently destructive and wasteful activity (for instance in the case of slate, less than one per cent of quarried material ends up on a building site) (3) and transportation and processing all add to the burden of pollution. Stone is, however, extremely durable and can often be recycled--the current vogue for gabion cages is one way of inventively re-using material. More pertinently, there is also renewed interest in exploiting the thermal properties of heavy masonry construction. The high thermal capacity of materials such as concrete, brick and stone enables them to store and re-radiate heat, reducing energy consumption, air conditioning and carbon dioxide emissions.

The principle of thermal mass is not new--it can be seen in the thick-walled, vernacular buildings of hot, dry, countries. Such architecture can also have extraordinary presence, as demonstrated by James Morris' images of mud buildings in West Africa (p60). Building with earth is probably one of the most environmentally sustainable forms of construction imaginable, the material being abundantly available, thermally efficient and completely recyclable, but as Morris observes, as cultures and communities evolve, the skill (and will) to build are gradually being lost. Yet though clearly impracticable to advocate a return to some primordial mud hut Eden, the accumulated wisdom of tradition still has a contemporary resonance in renewing humankind's historic relationship with materials and the built environment.

1. Materials, Form and Architecture, Richard Weston. London. 2003. Laurence King, p22.

2. New Stone Architecture, David Denne, London. 2003. Laurence King, p8.

3. Weston, ibid. p34.