Understanding the Long-Term Survival of Sandstone in Medieval Ecclesiastical Structures: Northern Ireland and Western Scotland

Abstract

Much of the world's, and especially Europe's, built heritage has been constructed using natural stone. Historically, it is a building material that is both aesthetically pleasing and durable. However, contrary to common perception, stone is not immutable, and many of our valued stone-built historic structures show obvious signs of age and decay. Advanced decay leads to the irrevocable loss of irreplaceable cultural heritage. Because of this, much effort has gone into understanding natural stone decay and the ways in which it may be managed. This focus on decay has meant that the reasons why certain stones survive are rarely examined. The long-term survival of stone over many centuries is a very complex problem---for example, factors that might be expected to cause decay can sometimes increase durability, depending on a specific combination of history, environment and stone character. To begin to understand this, a clear picture of history (events that have had impact on stone in the past), environment (the related processes that the stone is exposed to) and stone character (both material and form) is crucial. This chapter begins by emphasising the importance of each of these factors in understanding the long-term pattern of decay and survival of medieval sandstones. Following this, case studies are presented on the use and performance of sandstones in two medieval ecclesiastical structures in Northern Ireland and western Scotland---Bonamargy Friary and Iona Abbey, respectively