The Stone Heritage Group is one of the sector focus groups of Stone Federation Great Britain. It includes a wide range of stone companies, from quarry operators to conservation masons and consultants working in this sector, bringing to bear a wide range of expertise. 

The Stone Heritage Group is the arm of Stone Federation Great Britain dedicated to resourcing the heritage sector of the natural stone industry and promoting the use of Federation members for conservation and renovation projects.

Almost 50% of the membership of the Federation work in the conservation and restoration sector, either exclusively or as part of their overall business – after all, the skills of a stonemason today in many parts of the industry are not very different from those of masons 100 years ago or even a thousand years ago – and conservation and restoration  plays a significant part in the overall natural stone arena.

This month, we are taking a brief look at where to begin when considering the cleaning of natural stone buildings.

The cleaning of a building is no simple matter and there are special considerations which call for a high degree of expertise in all elements and stages of stone cleaning.

Specialised knowledge is necessary for the correct specification to be given for each building.

In the past, it was smoke emissions from the burning of coal that was responsible for much of the soiling of buildings. Today it is vehicle exhaust emissions.

Many studies have shown there are advantages to cleaning buildings on a regular basis.

The correct cleaning of natural stone is a priority for the sector, as much of the most significant architectural heritage of the country is made of stone.

Stone is one of the most durable of building materials and compares favourably with others from an economic point of view,  as well as from an aesthetic point of view, especially when maintenance and whole life costs are taken into account.

Nevertheless, proper maintenance is essential and if this is carried out periodically with suitable skill and understanding, the greater will be the environmental and practical advantages in the preservation of the structure. 

What must be stressed, however, is that in the wrong hands and by the use of the wrong processes for the kind of stone being cleaned, much harm can be caused. It can leave unsightly effects, some of which may not become apparent for some months after the cleaning has been completed and will be difficult, if not impossible, to remedy.

This is why it is imperative to involve a member of Stone Federation at an early stage when cleaning is being considered.

It is essential that cleaning should be carried out by fully trained operatives in order to avoid any damage being caused by an inappropriate cleaning method or an incompetent operative.

Remember that decay can often take place around an open joint or cracked stone that cannot be seen if they the surface is obscured by heavy soiling.

Reference should also be made to BS 8221 (part 1): 2000, Code of Practice for Cleaning and Surface Repairs. Stone Federation produces other relevant publications regarding cleaning, which can be found at www.stonefed.org.uk.

The Stone Federation Guide to Best Practice is based on the relevant parts of a number of British Standards relating to masonry cleaning and incorporates current best practice. It sets out the principal factors involved when deciding to clean and maintain buildings incorporating different types of masonry.

This document’s aim is to give advice as a guide, although it is by no means definitive. Variables exist with every project and no two projects are the same.