These notes are intended to provide some guidance to building owners or prospective purchasers and their professional advisors on the basic principles which should be applied in the repair of historic buildings. It is essential to identify causes of poor condition before specifying remedies and a careful and accurate diagnosis is crucial to the success of any repair project.

The principles of repair should be established at the outset of a repair project and should then be applied to create solutions to particular problems.

Principles of Repair

The main purpose of repair is to hold back the natural process of decay without damaging the character of the building.

Repairs must be kept to the minimum required to stabilise and conserve the building. The aim must be to achieve a sound structural condition to ensure long term survival.

The unnecessary replacement of historic fabric, no matter how carefully work is carried out, will have an adverse effect on the appearance of the building. It will diminish its authenticity and will reduce its value as a source of historical information. Some elements (i.e. roof coverings) require periodic overhaul or replacement but other parts (i.e. masonry) are likely to decay slowly in parts and may require a selective approach.

It is necessary to have a clear understanding of the historic development of a building before carrying out repair work. This may involve documentary research, architectural investigation and interpretation of the structure and its assessment in a wider context.

To repair or replace damaged fabric without first carrying out investigations of the causes, processes and rates of decay is to invite repetition of the problem.

Repair techniques must be compatible with existing materials and methods of construction. Generally, traditional, well proven methods should be adopted, however, sometimes structural failure may have resulted from inherent defects in the original design or specification of materials. In such cases, imaginative methods of repair may be appropriate.

Repairs should be carried out with no attempt to disguise or give a false impression of the age of the repair. The repairs should not be unnecessarily obtrusive, but it is acceptable to be able to differentiate between new and old work.

In the course of its life, an historic building will usually have been altered and extended several times in order to satisfy the needs and aspirations of successive owners. These alterations are often an intrinsic part of the history of the building and care should be taken to avoid wholesale removal of "non original" items.

Some elements of a building which were an important part of the design may have been lost in the past. A programme of repair may offer the opportunity to reinstate missing elements, providing that sufficient evidence for accurate replacement exists. Speculative reconstruction is always unjustified.

An historic building should be regularly monitored and maintained and provided with an appropriate and sympathetic use. This is the best way to secure its future and for keeping further repair requirements to a minimum.

(The above notes have been extracted from an English Heritage publication entitled "The Repair of Historic Buildings").