R.J. Schaffer

The background to the publication of R.J. Schaffer’s famous report on The Weathering of Natural Building Stones is very well summarized in F.M. Lea’s book Science and Building published in 1971. Here we learn that in 1920 the Imperial War Graves Commission (now the Commonwealth War Graves Commission) and the authorities of Westminster Abbey sought advice from the ‘Building Research Board’ on the weathering and preservation of natural building stone. At the same time there was pressure from both the Royal Institute of British Architects and the Society of Architects for work in these fields. In 1923 the Advisory Committee of the Department of Scientific and Industrial Research (DSIR) commented:

The decay to which stonework is subject, especially under the actions of impurities in the atmosphere of our large towns, is a matter of common observation and the question has become one of general economic importance… It constitutes a special problem which has engaged the attention of many investigators for a considerable time without, however, finding any generally satisfactory solution.

It was against this background that R.J. Schaffer began his work at the Building Research Station at Garston in early 1925. Over the next six years Schaffer considered over 250 books and papers on the subject of stone weathering and from this distilled DSIR Building Research Special Report No. 18 which over the last 70 years has become known almost universally as ‘Schaffer’.

At the same time Schaffer visited and studied many quarries in the UK – carrying out much of the work with F.H. Edmunds of the British Geological Survey. In particular, they undertook extensive surveys of the Jurassic Portland limestone quarries and Permo-triassic Magnesian limestone quarries in north-east England. The archive of site notes, photographs, samples and analyses from this work is at BRE and is still in regular use. Schaffer was also responsible for the preparation and examination of more than 6000 petrographic thin sections which are now known at BRE as the ‘Hurst Collection’ – after the technician who carried out the work.

Schaffer’s report is still very relevant and is a valuable reference work. The sections on the causes of weathering are still correct even though our style of building and pollution environment is now very different. This means that the balance between different weathering phenomena has now swung away from acidic pollution and ‘natural’ processes. The only part where thinking is differs significantly today is the section on ‘Preventative and Remedial Measures’ where current practice favours less aggressive cleaning methods and less harsh repair materials.

The last paragraph in the Report still seems particularly relevant to much of our work related to the service life of stone. In this paragraph Schaffer wrote:

The fact is, that the ‘life’ of a building stone is an indeterminate quantity, since its useful life may be regarded as completed when the material begins to look unsightly, or when its fails to carry the load imposed on it. The former depends on the æsthetic sense of the observer, the latter on innumerable structural factor. Nevertheless, the difficulty of interpreting the tests in terms of years cannot be considered to detract from the value of the laboratory examination.

‘Schaffer’ has remained in print for most the last 70 years which is in itself a testimony to the continuing relevance of the findings, and so it is a great pleasure to write an introduction to this latest edition.

Tim Yates B.Tech(Hons), Ph.D(London)

Tim Yates spent four years as a field archaeologist before reading Archaeological Sciences at Bradford University. After three years at University College London researching the analysis and geochemistry of Holocene carbonate sediments he joined BRE in 1986 as a Higher Scientific Officer to compile and edit the report of the Building Effects Review Group on the effect of acid deposition on buildings and building materials.

After BRE was privatized in 1997 he took on responsibility for the team researching heritage buildings, stone, and mortar. This team is currently carrying out research on the durability and testing of natural building stone. Much of this research relates to the development of European standards for the testing and specification of natural stone for cladding, masonry and flooring.

The Team is also responsible for undertaking consultancy projects on natural stone and in the last 10 years more than 500 projects in the US, Canada, Croatia, Bosnia, Israel, Abu Dhabi, Hong Kong and Singapore as well as the UK and Ireland have been completed; many of these relate to the deterioration of natural stone or to the selection and testing of stone for construction.