Stonecleaning: A Guide for Practitioners

Introduction to the Guide

Of all the changes to which buildings can be subjected, stonecleaning is one of the most visually dramatic. It is a process that changes not only the fundamental appearance of buildings but also the environmental context in which these buildings exist.

Over the last decades, stonecleaning has grown into a multimillion pound industry, although the history of stonecleaning can be traced back much further. Much of the more recent stonecleaning activity has taken place as part of urban renewal and regeneration programmes.

Without the visual improvements which stonecleaning has brought about, valuable parts of the urban fabric may well have been lost to redevelopment. Stonecleaning work has been encouraged by a number of grant awarding bodies, partly because of the assumed aesthetic benefits which are thought to accrue from stonecleaning, and also as an attempt to regenerate economically depressed urban areas. Stonecleaning has brought about dramatic improvements in the appearance of many urban buildings particularly in cities blackened by the industrial pollution of the past. The colour of stonework and the architectural detailing of buildings become more apparent following cleaning. The net result of this activity has been to stimulate a pride and interest in our architectural heritage which it is difficult to imagine any other activity doing to the same extent. Stonecleaning has also had a less tangible "psychological" effect in urban areas. For example, following stonecleaning the reflected light at street level is increased leading to a brighter, less oppressive atmosphere. The inhabitants of many tenement properties have welcomed the improvement to their living conditions which stonecleaning has brought. In many cases these improvements have been part of general refurbishment programmes.

While the visual improvements brought about by stonecleaning should not be underestimated, neither should be the dangers. Increasingly, concerns have been expressed at the irreversible damage caused to some buildings by stonecleaning. Evidence abounds of situations where unskilled operatives, using inappropriate techniques and undue haste have caused permanent damage to buildings. The situation is often exacerbated by the process of tendering for stonecleaning contracts, where the unwary client simply chooses the lowest tender price without detailed consideration of the possible implications of that decision. In this situation the reputable stonecleaning company, which is more likely to devote greater time, care and resources to the contract cannot match the price of the unscrupulous operator whose motivation is solely financial. The consequence of this has been that some of the more reputable companies have withdrawn from stonecleaning work, leaving the way clear for the less scrupulous.

While in the past there have been no established mechanisms in place for the training or licensing of stonecleaning contractors, this is currently being addressed by the more reputable companies and the standard setting bodies. However, it is possible to purchase, without restriction, equipment and chemicals capable of doing great damage to masonry.

The Practitioners Guide contains information on:

• the characteristics of sandstones,
• biological and non-biological soiling of buildings,
• aesthetic considerations with respect to cleaning,
• notes on physical and chemical cleaning methods,
• guidance on testing methodology prior to cleaning of facades and
• notes on health and safety and planning issues.

The above information is copyrighted to Historic Scotland and The Robert Gordon University and if quoted should be referenced as:

Copies of this book are available through the Scottish Conservation Bureau of Historic Scotland at:

Prices, order forms and information on other Historic Scotland publications can be obtained from the above address or on the Historic Scotland web site at: http://www.historic-scotland.gov.uk/