1.1 Purpose and Content of the Book
Our ambition in writing this book is to enhance the readerās understanding and hence appreciation and enjoyment of building stones and stone buildings. Stone has been used structurally and decoratively for many centuries throughout the worldāand stone has its own special appeal because of its natural occurrence, its strength and its surface appearance. Today, many old stone buildings still survive, intact or in ruins, depending on their resistance to the many factors contributing to their degradation. Moreover, stone continues to be used extensively as decorative cladding to new and architecturally dramatic buildings.
As an introductory example of a stone building, in Figure 1.1 we illustrate the Jewel Tower in Westminster, London which, as its name implies, was built in 1365 as a secure repository for Edward IIIās jewels. The Tower, built with Kentish ragstone (a type of limestone), has survived to this day, despite the 1834 fire which destroyed the adjacent Houses of Parliament, and it is now part of the Westminster World Heritage Site. Given that buildings like this, built mainly or partly from quarried stone plus more modern ones with stone cladding, are all around us, the purpose of this book is to present an overview of the whole subject together with the key related supporting subjects in order to enhance the readerās appreciation of building stones and stone buildings. It is a fascinating topicārich in history, geography, geology, mechanics, chemistry and architectureāand it is our objective to present and explain the related information in a simple, structured, coherent and illustrated way.
There has been a long history of stone use from the Paleolithic era, through the Mesolithic, Neolithic, Bronze Age, Iron Age and Roman times, plus the relatively more recent Anglo-Saxon, Medieval, Post-Medieval and Industrial periods right up to the present day. Stone, especially flint, has been used extensively for tools and buildings from the early Ages. In both our Frontispiece and Figure 1.2, the megalithic nature of Stonehenge is illustratedāone of the most iconic Neolithic monuments in Europe. In Figure 1.3 a detail of the use of flint for constructing the walls of a Roman bathhouse in England is highlighted and in Figure 1.4 a portion of Trajanās column (constructed to commemorate his victory in the Dacian wars) shows Roman wall building. In Figure 1.5 the more recent and extraordinary skills of the 15th century Inca masons are demonstrated, particularly in preparing such perfectly interlocking stone blocks for their dry stone walls in Peru.
Building stones are generally obtained from quarries, although there are exceptions such as stones found on moors and the use of stones from ruined buildings, as was the latter case in Hertfordshire, England, where flints and tiles from the abandoned Roman town of
(a) The Jewel Tower (built ca. 1360s) to house Edward IIIās treasures.
(b) Rough Kentish ragstone to the right of the entrance. This limestone has been used extensively in the SE of England.
Figure 1.1 The Jewel Tower located near the Houses of Parliament, Westminster, London.
Figure 1.2 The 4,500-year-old late Neolithic Stonehenge sandstone monument located on Salisbury Plain, Wiltshire, England (see also the Frontispiece).
Figure 1.3 Portion of a flint wall in a Roman Bathhouse, Welwyn, England (~0.7 m width).
Figure 1.4 Roman brick/stone building, as shown on Trajanās Column completed in AD 113.
Verulamium were scavenged for use in the construction of St. Albans Abbey. In the case of quarries for building stone, as opposed to open pit mines excavated for metallic ores, financial considerations generally dictate that the rock stratum being exploited in a quarry should be relatively near the surface and easily accessible. Moreover, the quarry should ideally be located near to where the stone is to be used, although nowadays this latter criterion is not so critical, especially for decorative stones that tend to have higher values and hence can be transported further, as indeed is the case for the popular Carrara marble from Italy which we highlight later in Chapter 4.
Figure 1.5 The interlocking dry stone walls of Sacsayhuaman, an ancient Inca fortified complex constructed of huge, megalithic stones, some weighing over 100 tons. They fit together with an extraordinary precision (a sheet of paper cannot be slid between them) and it is still not known how these limestone blocks were cut. (Courtesy of N. R. Barton)
So our story should begin with the origin of stone by noting geological aspects that determine both the geography of different types of stone and the associated quarrying process, plus cutting, fashioning and transporting the stone, as illustrated in Figure 1.6 by the granite blocks (known as setts) being used for a market place surface. Once excavated, shaped and used for the exterior of a building or other structure, the stone begins its exposure to the elements and its long and inevitable process of deterioration, decay and journey āback to the Earthā via the different physical, chemical and biologically associated forms of degradation. Somewhere along the line, an old building stone may be replaced by a newer version but this process is fraught with problemsāa subject which we discuss later in Section 7.3.5.
Figure 1.6 Granite setts being installed in a road surface.
As noted in the Preface, while walking in a countryside environment it is satisfying to be able to name a particular species of bird or flower that one passes, and the same applies to the identification of the different types of building stones in the built environment. Some of these stones are instantly recognisable from their texture, such as the Rapakivi granite from Finland with its characteristic appearance (geologically known as ovoidal, orthoclase phenocrysts), Figure 1.7, and which can sometimes be seen as a decorative stone on the exterior of buildings and often on the counters in CaffĆØ Nero coffee outlets. Another easily recognisable stone is Yorkstone, Figure 1.8. So, following Chapter 2, which provides an overview guide to the geological origin of building stones and associated subjects, Chapter 3 is devoted to the descriptions and illustrations of granites, volcanic stones, limestones, sandstones, flint, metamorphic stones, breccias and conglomerates, plus a variety of artificial stones: Coade stone, terracotta, faience (glazed terracotta), brickwork and concrete. Although most of these latter materials do not have the same character as natural stone, they certainly do have various economic, decorative and durability advantages.
Some relatively less used building stones can have clear visual characteristics, but not be so easily identified when used some distance from their origin; an example of this is the Runcorn sandstone from the west of England used for All Saints Church in Hertford in the east of England, Figure 1.9. However, we hope that the guidance given in this book will
Figure 1.7 The texture of Finnish Rapakivi granite, widely used as a decorative stone (sample ~0.3 m width). The word āRapakiviā in Finnish means āweatheredā or ārottenā due to its appearance, but the granite is actually significantly resistant to weathering.
Figure 1.8 Yorkstone (a sandstone) used for pavements and road construction, Rochester, England.
enable recognition of the type of such building stones, if not the actual name of a particular variety.
Figure 1.9 The Runcorn sandstone exterior of All Saints Church, Hertford, England. (Stone bedding texture photographically accentuated.)
Chapter 4 describes the life of a building stone from the initial quarrying and preparation through to its eventual deca...
