The Principles of Conservation

Buildings and monuments sometimes require repair works to stabilise or conserve them to ensure their long term survival. There may also be a need to appraise an historic structure for other reasons such as a change of use or structural alterations.

Our first objective with any existing building is to try to understand how it behaves structurally. In order to do this an initial inspection is carried out which may be followed by a detailed structural inspection or opening up for an investigation. A thorough understanding of the historic development is also required and the historical research can be carried out by us or the conservation Architect or Surveyor. The initial investigation once completed will not end at this point because there will be opportunities for an increase in our knowledge of the building once the repairs or alteration works to the structure are under way. Previous often piecemeal modifications to the building can make our analysis of the structure difficult so a proper investigation can be a rather lengthy and often iterative process.

Existing buildings have usually distorted to accommodate the forces acting upon them and have reached a point of equilibrium in their structural form. It is usual for the many elements in the building to combine to prevent collapse. Care is needed therefore when wishing to remove or alter parts of an existing building as the load paths are not always discrete.

We do not place great emphasis on structural calculations when analysing existing structures. Indeed, Codes of Practice, Building Regulations and British Standards are not applicable. The fact that a timber column has carried an existing load for a considerable period of time is usually proof enough that the element is satisfactory even if the structural calculations cannot confirm that this is the case. Obviously care is needed when increasing load on or physically altering a structural element to ensure that the revised structure will be sound. It is here that we turn to available data on material strengths or we might have existing materials tested for strength characteristics to assist in our appraisal of the structure.

We will also want to look at the quality of the materials in the construction and try to determine whether there is a fear of continued decay. Clearly this will affect our appraisal of the strength of the building and recommendations for repair to ensure its future performance. We try to strengthen and stabilise structures insitu and effect the minimal amount of repairs required to ensure the long-term survival of the building without damaging its character or unnecessarily disturbing historic fabric. In our view repairs should be carried out honestly without any attempt to disguise them. However we work with professionals and building owners and Local Authorities who have their own views about the ways in which repairs should be effected and we are often guided by them as to the approach that must be taken.

Having put forward the results of our investigations along with alternative structural proposals for repairs we then agree with the project leader the best approach to take for a particular building.