David Francis is a hands-on mason who has specialised for many years on the memorial side of the stone industry. He was Technical Advisor to the National Association of Memorial Masons, writing manuals and City & Guilds Qualifications. If you have an issue regarding any aspect of memorial masonry, David is happy to help. Send your questions or comments to David at nss@qmj.co.uk
Many older, dilapidated monuments should certainly be saved. A burial ground with piles of broken or fallen memorials looks a mess and can be difficult to maintain. But at what point does a mason recommend the memorial is beyond repair?
Some monuments are significant and need to be preserved for historic or sentimental reasons. These memorials, maybe because of their condition or the thickness of the stone used, need special care and skill in their renovation and specialist conservation skills could be required.
Listed memorials can be a problem. Precisely what kind of listing the memorial has is important. It may not be English Heritage that has decided it should be listed but the Local Authority or even the local Historic Society.
In order to renovate it, we need to know why it was listed. Is the relevance the person who is buried in the grave or is the memorial itself of some merit because of its architectural or aesthetic value? Sometimes the owners of the grave do not know of the Listing. They might still have the Right of Burial.
If the Listing has come about because of the significance of the person buried, it may be possible, with the appropriate approvals, to construct and install a new monument. Of course, any work on memorials must have approval from the relevant authorities and any others concerned.
Cleaning must be carried out with care so that the surface of the stone is not damaged. Specialist cleaning systems may be required for listed or heritage monuments depending on the type of material.
When refixing memorials, they do not need to be taken apart and re-dowelled when there is no evidence of movement in a joint. Separating firmly fixed parts of a memorial may break, or compromise, the strength of the material and the joint.
Any loose parts of a memorial should be firmly refixed with dowels.
The dowel sizes should be chosen carefully so that the strength of the original material is not compromised. The length of dowel is more important than its diameter. As long as the hold for the dowel has been drilled accurately, quite thin pieces of stone can be refixed in this way.
It is better to set the dowelling into thin materials and allow the cement or adhesive to set before fixing. On semi-transparent materials, such as white marble, white cement can be used to secure the dowel.
For very thin or decaying materials, the stone can be strengthened by reinforcement on the back, as long as it will not be seen. A thin backing material can be used to support the stone and increase the thickness.
Experience over hundreds of years has shown that quite thin slate retains its strength as long as the material is of good quality.
However, slate can delaminate along its cleavage planes – it is, after all, what makes it such an ideal roofing material. Once it starts to split, there is little that can be done to make a repair as the layers peel and cannot be pulled back together.
When marble erodes, the soundness of the material must be checked for integrity before any work is undertaken.
Eroded sandstones and limestones might need surface consolidation. Granite 50mm thick is not unusual, especially for headstones on ashes plots.
Consolidating the surface of material is not easy. If the stone is porous it is possible to use a product to harden it against the weather. Acrylate products, such as those employed successfully by conservationists, can be used but the application rules must be strictly adhered to.
Useful information about work on old materials is contained in the English Heritage document ‘Caring for Historic graveyard and Cemetery Monuments’ available from the English Heritage website www.english-heritage.org.uk/ publications