20 Apr Disguising Intervention
When undertaking repairs to historic structures, PAYE will always try and match the original construction in both building material (whether that be brick, stone, precast material) and the appropriate binder/mortar/render – this follows the widely adopted mindset of ‘like for like’ repair.
Often conservation professionals feel that a building should be able to tell its own story and that the chronology of previous intervention reflects this. These changes, unless damaging to the object/building are therefore generally retained, allowing previous repairs to be visible and gifting the building a level of historic honesty. This mindset is of course not always shared with clients and some custodians, who would place a greater value the aesthetic harmony above this. When this is the case, we will always try to take on board the request, but equally try and remain true to our developed ethic.
Kensington Palace (before)
Kensington Palace (after)
Whilst not a rigid set of rules, PAYE Conservation try with their best endeavours, to apply the following general philosophy of approach to project work, this includes:
- Wherever possible, a philosophy of minimal intervention should be adhered to. Minimal intervention is the concept of low-key intervention which involves keeping as much as you can and changing as little as is feasible.
- Wherever possible, any intervention should remain reversible. To allow full removal without damage in case a better solution should become available in the future.
- Wherever possible, like for like repairs will be carried out and any unprecedented materials introduced, kept to an absolute minimum.
Wherever possible, new repairs should not disturb the aesthetics of the architecture. Attempts to disguise or artificially age interventions are not essential, but there is no need for new interventions to be visually obtrusive. They should be discernible on close inspection, but we should try not to allow them to detract from the visual integrity of the original structure.
- Wherever possible, all replacements/repairs should only be carried out with the assistance of documentary evidence; no speculative works should be undertaken.
- When cleaning an object/building, care should be taken not to over clean – a developed natural patina should not be completely lost, allowing the building/object to retain an air of historic integrity.
- Historic repairs (where not proving deleterious in causing damage to the building/object) may be retained, allowing the building to retain some chronology.
- All intervention should be documented in both written and photographic form. Ideally showing a pre-existing record as found, detail of work in progress and on finally on completion.
- Obviously, all of the above statements are somewhat subjective, and so as we have relayed many times before, each project must always be considered individually, in context and take into consideration a range of factors which both directly and indirectly affect it. Where possible, this decision-making process should always be recorded.
Where matching original material cannot be achieved, for example where the original quarry has closed, or where a number of brick replacement needs to be completed but the matching brick colour does not match fully, where the original material has developed a natural patina which is to be retained, or more often, where the client would prefer the repair to be fully disguised from the outset and not allowed to naturally weather – using a colour wash/tint can be championed as a quick and cost-effective solution.
Sydmonton Court (before)
Sydmonton Court (after)
The process involves the application of colourfast natural oxide pigments bound within a liquid Potassium Silicate (K2SiO3) binder. The Potassium solution penetrates the surface of the brick and creates a colourfast breathable coating which is resistant to extremes of weather and UV exposure. Experience has shown that this tinting process is a permanent modification of the surface colour, with the treatment having no adverse effect on the durability or other performance attributes of the masonry.
Where a variety of different coloured materials (brick/stone) have been used for patch repairs, initial trials are always carried out to determine the best colour tint for each location, allowing for a subtle blend of application which is then difficult to readily identify on completion.
PAYE have technicians who have been specialising in this field for over 20 years and our skilled tradesman are among the most experienced in the industry. A few examples of recent projects where tinting has been used to great effect include:
4 The Grove, Highgate – Grade II*, Private Client. Historic ‘soot wash’ applied over brick repairs to tone them to match the rest of the 16th Century building.
Sydmonton Court – Grade II*, Private Client. Tinting applied to new lime mortar and brickwork to match 17th Century brickwork
Kensington Palace – Grade I, The Royal Household. Tinting completed to tone down new mortars around Granite sets in a 18th Century courtyard
Upper School, Eton College – Grade I, Eton College. Coloured tint applied over isolated brick replacements to tone them to match the rest of the 16th Century building.