Limestone decay

Many of Oxford’s most historic buildings could be preserved more effectively, thanks to research into how and why limestone building blocks decay.

Many of Oxford’s most historic buildings could be preserved more effectively, thanks to future research into how and why limestone building blocks decay.

Scientists from the Oxford University Centre for the Environment (OUCE) are involved in a 3-year project to improve understanding of how and why limestone decays. The project is funded by the Engineering and Physical Sciences Research Council (EPSRC) and will begin  in January 2006.

A key element in the project is the development of optical sensors that can monitor how limestone is affected by traffic pollution, road salt, temperature, humidity and wetness, and detect subtle changes in the stone caused by changing moisture levels and salt movement.

Test sensors will be installed in a boundary wall at WorcesterCollege, Oxford and in other limestone structures around the country. Information will be fed by the sensors, via fibre-optic cable, to data loggers and analysed to see how decay correlates with environmental factors and with the limestone’s physical, chemical and mineralogical characteristics.

Limestone has been used as a building material in Oxford and in many of the UK’s most famous landmarks for centuries, but it can decay due to pollution, weather and other factors. This can be disfiguring, expensive to rectify and, if left untreated, may eventually lead to a building’s collapse. By improving understanding of limestone decay, the new research will make it easier to develop ways of tackling the problem.

The front wall of Worcester College shows patchy limestone decay.

Dr. Heather Viles of OUCE is co-leader of the project, which also involves scientists and engineers from Queen’s University Belfast and City University London.

‘Basic knowledge about limestone decay exists, but we don’t know why it takes place in unpredictable fits and starts or accelerates in some parts of a building but not in others. This understanding is vital to enable action to be taken before decay spirals out of control, but also to ensure conservation decisions don’t lead to unnecessary block replacement and expense,’ said Viles.

‘This is the first time that expertise in geomorphology, physics and civil engineering has been linked together and applied to the problem of rapid limestone decay. As well as informing anti-decay strategies, our research will generate knowledge about types of limestone best suited to particular environmental conditions, and so will benefit not just renovation but new-build projects too.’

Many famous landmarks in Oxford and across the UK could benefit from the project. Limestone is the main construction material used in many of Britain’s most impressive buildings, such as St Paul’s, Lincoln and Wells cathedrals.