The Use and Conservation of Totternhoe Stone
Precis of Dissertation
Aims and Objectives
The aims and objectives of the dissertation are to conduct a detailed investigation into the use of Totternhoe Stone since early times, the problems encountered today and the current methods of conservation. These were pursued by undertaking secondary level research into archive material, published material, site investigation and consultation with those involved in the subject.
Source of Totternhoe Stone
Totternhoe Stone is a hard chalk stone that was originally mined at Totternhoe in Bedfordshire. This stone occurs in beds throughout Berkshire, Oxfordshire and Buckinghamshire with the thickest beds developed through Bedfordshire, Hertfordshire and Cambridgeshire. There is a much thicker bed found in a geological channel feature at Totternhoe and this is where the medieval mines were located. Today Totternhoe Stone is extracted as a small scale concession from the open cast quarry at Totternhoe; the overburden is used for agricultural lime.
Use of Totternhoe Stone
Totternhoe Stone has been used as a building material since Roman times. Production of the stone probably reached its peak during the church rebuilding programme that took place after the Norman Conquest. Totternhoe Stone continued to be used throughout the middle ages and through to the end of the nineteenth century. Today it is available once more for small scale conservation work. The stone has been used for structural work in columns, arches and external walls. It has also been used externally for facework and ashlar. Internally it has been used for decorative features and screens. Totternhoe Stone has been used across a wide area centred on Totternhoe in Bedfordshire. It was particularly popular because it is one of the hardest stones that can be cut by hand.
Problems in Buildings
Where not protected with limewash, Totternhoe Stone has a limited life. It is a relatively soft stone and if exposed to the weather it will decay rapidly mainly as a result of frost action and salt crystallization. This can lead to major structural failure where extensive repairs will be required. The frost action and salt crystallisation will cause rapid exfoliation of the stone eventually leading to the need for replacement. Defective building construction can also leave the stone unnecessarily exposed to inclement weather and other forms of decay. Previous harmful intervention, in particular repointing in cement mortar and other cementitious repairs will increase the rate of decay.
Solutions in Conservation
The methods of repair and maintenance will require careful consideration to avoid unnecessary or incorrect interference with the stone structure or surfaces. Conservation philosophy will require the minimum intervention in order to retain the historical aspects of the building. Where structural failure has occurred the repairs are likely to be quite radical in their nature although where possible alternatives to complete rebuilding are preferred. The use of lime is of paramount importance in conservation work, either in the form of limewater, lime mortar, limewash or shelter coating. Where following the "lime method" the repair will involve consolidation with lime water, redressing or carefully removing decay back to sound stone, mortar repairs and finishing with a shelter coat. Replacement of defective stone is a last resort and Totternhoe Stone is now available for this work rather than the previous use of tiles. Bath stone may be used in the more exposed positions. Shelter coating may not always be visually acceptable to the building owner and the repaired or replaced stone may be left exposed.
Conclusion
The last 150 years have seen much restoration work, some which was destructive, and the old methods of protecting Totternhoe Stone have died out. Conservation philosophy requires that all repairs should conserve as found. Consolidation of decayed stone is used to retain the historic interest in particular with carved work and Totternhoe Stone is used where there is no alternative to stone replacement.
Recommendations
All conservation work should follow the original methods which have been proved over more than 1000 years. Where possible the existing Totternhoe Stone should be conserved and consolidated to retain the historic interest. Replacement stonework should use new Totternhoe Stone to match the original and to support the small scale quarry operation. The traditional materials and skills have been resurrected for conservation work. We should also be using limewash to protect the Totternhoe Stone.
Stuart Little - February 2001
RICS Postgraduate Diploma in Building Conservation