Chapter 9 Stone
ROBERT INKPEN^1 AND ERIC MAY^2
(^1) Department of Geography, University of Portsmouth, Hampshire, PO1 3HE, UK
(^2) School of Biological Sciences, University of Portsmouth, Hampshire, PO1 2DY, UK
1 INTRODUCTION
Degradation of stonework is a major aesthetic and economic problem for his-
torical buildings as well as for contemporary buildings. Oxford University,
for example, recently spent £3.2 million renovating Duke Humfrey’s Library
and other rooms in the Bodleian Library (The Guardian, 22 April 2003, Joel
Budd). The nature of degradation can vary from simple discolouration of the
surface to the development of micro-scale weathering forms through to
potentially structurally-damaging changes. Degradation can be viewed as a
general term covering both the weathering of stone, that is, its alteration in situ,
and the removal of weathering products arising from erosional processes. Often
in the scientific literature, weathering and erosion are used interchangeably.
Both types of processes are needed to alter stone material and then remove it
from the buildings, so conservation practices have looked at means of pre-
venting each set of processes. Evaluating the stage at which degradation becomes
a problem requiring remedial measures depends upon its identification as a
problem by appropriate building surveyors or architects and the feasibility,
often economics, of available conservation measures. Conservators often find
an importantproblem, for conservation must address the variable nature of
both the material itself as well as the response of the material to weathering
processes and agents. Variation in stone properties and in the nature of the
weathering agents that attack it often result in complicated patterns of deter-
ioration across a building, as well as periods of apparently accelerated degrada-
tion and periods of seemingquiet. This chapter provides a simple framework
for looking at stone degradation and then uses this to assess in greater detail