Building conservation has been influenced and developed by a variety of philosophies and charters, primarily since World War II. These include the Venice Charter (1964), the Granada Convention (1985), the Burra Charter (1979-2013) and European Conventions on the Protection of Architectural and Archaeological Heritage (1997).
These charters have aimed to protect individual monuments and buildings, to the cultural significance of entire places such as cities and cultural landscapes. Area-based conservation is increasingly recognised internationally as a counterbalance to a homogenisation of world culture, as well as being encouraged by growth in cultural tourism.
Use of appropriate materials and methods
The use of appropriate materials and methods in repairs and interventions is essential in order to ensure the long-term survival of an old building. Many materials such as cement and plastic-based products can damage traditional building materials and result in accelerated decay of the building. As a simple rule, use of ‘like-for-like’ materials and techniques is the best way of conserving an old building.
Respecting earlier alterations of interest
Later alterations and additions, such as porches and plate glass windows and certain decorative features can contribute to the character of an old building. In order to appreciate the overall integrity of a structure, it is always important to respect the contribution of different stages of its historical development. Fashions come and go, and a prevailing taste for removing certain features may deny future generations the opportunity of fully appreciating the historical development of an old house. Only in certain circumstances, based on research and informed judgements, should the removal of later alterations be considered.
Restoration means returning a building or structure to a known earlier state. Ideally, restoration should not result in the loss of historic fabric or features. For instance, it may be inappropriate to remove late 19th century plate glass windows in a Georgian house and replace them with 21st-century replicas of Georgian-style, small-paned windows. In other circumstances, it may be necessary or desirable to restore missing features such as windows, doors and joinery or plasterwork features during the course of repairs and renovations. In such cases, the design of new features should be based on physical evidence either from the subject building or adjoining houses in order to avoid conjectural restoration.
The use of techniques and materials which allow a repair or alteration to be reversed at a later date without loss of historic features or fabric is always to be preferred. Removal and disposal of old doors and windows is an obvious example of an irreversible intervention. A less obvious example would be the use of modern materials such as resin, concrete or cement which form a tough, almost unbreakable bond with old building materials, making reversibility without damage difficult at a later date.