“Architectural conservation describes the process through which the material, historical, and design integrity of mankind’s built heritage are prolonged through carefully planned interventions.”
The Irish Department of Arts, Heritage and the Gaeltacht (2011) outline thirteen principles for conservation best practice.
1) Keep the building in use
This will ensure the maintenance and upkeep of the building. Usually, the original use for which the structure was built will require the least amount of change.
2) Researching and analyzing
Thorough research of the building’s historical development is important in understanding its particular significance. This should include not only the building in question but also its surrounding cartilage and other structures.
3) Using expert conservation advice
Building conservation is a specialized discipline and the method of work needs to be specified by experts with a knowledge and experience of historic buildings. Expert advice should be sought at all stages of a project from planning application through to completion.
4) Protecting the special interest
The character and special interest of a protected structure can be damaged by inappropriate works. Old buildings should not be expected to perform the same way as modern buildings in terms of structural strength, durability of materials or thermal insulation. But old buildings often have qualities which cannot be reproduced, such as craftsmanship and a patina of age which is irreplaceable and very often cannot be replicated.
5) Promoting minimum intervention
This is best summed up as, ‘Do as much as necessary and as little as possible’. Dramatic intervention is rarely appropriate and can damage the special interest of the building. Replication of original features is appropriate where evidence exists to aid the reinstating. Returning the appearance of a structure to a notional date in time is not generally permitted. Usually interventions should be identifiable as such and not create a false historic impression.
6) Respecting earlier alterations of interest
Different periods of alteration can inform the social and architectural history of the built heritage. These contributions to the building’s story must be respected and preserved. Likewise, any new alteration will in turn become part of the building’s story and therefore must be a positive intervention.
7) Repairing rather than replacing
Authentic fabric should be preserved rather than replaced by non-original materials.
8) Promoting honesty of repairs and alterations
Repairs should be carried out without attempt at disguise or artificial ageing. Deliberately obscuring alterations confuses the historical record of the building.
9) Using appropriate materials and methods
Traditional materials and methods should be used where possible. The use of modern materials and techniques should only be used where their appropriateness is supported by scientific evidence or where they have proved themselves over a sufficient period of time.
10) Ensuring reversibility of alterations
The use of processes which are reversible allows for future corrections without causing damage to architectural heritage. Alterations which may cover elements of special interest in this way may then be reversed at a later date.
11) Avoiding incremental damage
When altering a protected structure thought must be given to the effect the alteration might have on the bigger picture, such as the effect that altering the appearance of one terraced house would have on the overall terrace.
12) Discouraging the use of architectural salvage from other buildings
The reuse of architectural features from elsewhere can confuse the authenticity of a protected structure, and creating a market for salvaged building materials encourages the dismantling of other old buildings.
13) Complying with building regulations
Compliance with building regulations may not be appropriate and is not required in relation to work on historic buildings. Satisfactory levels of compliance may be demonstrated by alternative means.