IHBC Yearbook 2014

30 Y E A R B O O K 2 0 1 4 Repairs also need to be based on the correct diagnosis of defects. This requires an understanding of the building, its design and materials, and their decay patterns and rates of decay over time. It is all too easy to assume the worst and take a disproportionate response to erosion, distortion or cracking that may have been evident for many years, inherent in the design or part of the special historic character of the building. Often, monitoring defects over a period of a year or two will put things in perspective. The need for detailed professional survey and recording of historic buildings to guide repairs is clear. MINIMUM INTERVENTION Assuming that repairs are really necessary for the long-term survival of the building, the key to preserving historic character and significance is ‘conservative repair’, or keeping repairs to the minimum necessary to ensure structural integrity, arrest or delay deterioration, and ensure continued function.4 This even applies if the ‘function’ is merely as ‘a ruin in the landscape’. Minimum intervention will ensure that repairs do not cause unnecessary damage. Historic buildings are a finite resource and the principle of minimum intervention also makes economic and environmental sense. Many historic elements were designed to be repaired in a minimal or piecemeal fashion. Timber windows, timber frames, masonry and brickwork can all usually be repaired by piecingin matching materials. At the same time, there are elements such as roof coverings that will eventually require comprehensive replacement to ensure that they remain safe or weatherproof. TRADITIONAL MATERIALS AND TECHNIQUES Materials used for repairs will never be exactly the same as historic materials but should be as close as possible and compatible so that they do not introduce damaging chemicals or stresses or disfigure the appearance of the building. To ensure that repairs do not cause unnecessary damage, materials used in repair work should be fitted to the surviving historic materials, not vice-versa. Occasionally, repair work may require the use of modern materials or detailing to correct past design defects which are causing active deterioration. However, this approach is only appropriate in cases where it allows more of the historic fabric to be retained and if the repair can be achieved unobtrusively. Modern ‘miracle’ materials or treatments have too often been found in retrospect to be damaging to historic fabric and repairs to historic buildings are not the place for experimentation. Perhaps the most widespread example of the use of damaging modern materials in repair work is the repointing of hundreds of our most important historic monuments with cementitious mortars, which irreparably damaged the masonry by introducing salts and inhibiting drying out. The wisdom of using tried and tested traditional materials and craft-based techniques that can last for hundreds of years is now more commonly accepted for repairs, but other old buildings should not be cannibalised to provide ‘authentic’ materials such as roofing slates. Part of the aim of using traditional materials and techniques should be to help support suppliers and craftspeople in business so that they remain available for repairs to other historic buildings, to benefit the wider heritage. Statue of Lady Jerningham, Berwick-upon-Tweed (1908, Grade II): the marble statue was treated with an irreversible sealant and was featured on the BBC television series ‘Tomorrow’s World’ in 1975 A conservator from Nicolas Boyes Stone Conservation works on the statue. Extensive conservation work had to be carried out in 2007 to prevent serious cracking and spalling attributable to the ‘innovative’ treatment. Many of the balustrade panels at Brizlee Tower, Northumberland (1781, Grade I) were beyond recovery due to rusting of the original iron pins and cramps and had to be completely re-carved in matching sandstone. Stainless steel and bronze cramps and pins were substituted in the repair work. Rebuilding the balustrade at Brizlee Tower included adding stainless steel posts to support and reinforce the balustrade to make it safe.

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