Condition assessment for building stone conservation: a staging system approach

Trofimov and Phillips (Geomorphology 5 (1992) 203) suggest that the ultimate goal of any science is to predict the behaviour of entire systems. With regard to the decay of building stone, making accurate predictions of stone behaviour remains an elusive goal but given our improved understanding of decay dynamics it should be possible to provide a forecast of likely system behaviour. However, forecasting system behaviour requires classification of the system state with the classification, whether formal or informal, founded on knowledge of the factors that control response. In the context of building stone decay these controlling factors include, structural properties, mineralogical properties, inheritance effects, contaminant loading and natural change. In trying to formalise building stone condition assessment and incorporate a forecast component, an analogy can be made between the requirements for classification and treatment determination of cancer patients and the approach to condition assessment and conservation of stone structures. In medicine, one of the most widely used and refined patient assessment schemes is the TNM Staging System. The rationale underpinning the TNM Staging System has many similarities with approaches to building stone assessment in that it seeks to impose a more formal structure on condition assessment that provides a commonality of approach, language and meaning and a procedure for forecasting the extent of remedial intervention required and outcome in terms of ‘life expectancy’.