The conservation agenda influences many of our projects. We have over 30 years experience ranging from working on the Glasgow School of Art to the repair and conservation of Rosslyn Chapel. We have worked with a host of organisations with broad interests in conservation such as Glasgow City Heritage Trust and The National Trust for Scotland and others with more specific agendas such as the Archdiocese of Glasgow and Church of Scotland General Trustees.
We are repeatedly finding that the same question is arising - how do we deal with the conservation challenges which arise where the original materiality and detailing has not stood the test of time and, after investigation, are found not likely ever to do so? Worse still, how do we deal with the broader consequences of that failure in the ripple effect on the related fabric? Standing back from these issues we are faced with the question of whether, as conservation architects, we are treading too delicately around the issues that shape the way forward to reconcile the issues, ensuring conservation and long term integrity of our built hertiage.
An ever-growing undercurrent to our considerations is accumulating evidential experience across a number of buildings of rapidly increasing deterioration of building fabric. Is this a tangible sign of the changes in our wet climate? Reviewing weather data shows that there is evidence of increased volatility in environmental conditions, in particular rainfall - a 21% increase in annual rainfall across a 40 year period of detailed recording and significantly more heavy rainfall events, particularly in the winter.
A case in point is the issue of roughcast (or harling as it is now often referred to) - a protective coat to many of our historic buildings and in particular at Mackintosh's Hill House, Helensburgh.
A seminal study by Andrew Wright on the history of the roughcast specification (dense, impermeable mix rich in Portland cement) and a review of its performance on the Hill House has raised many significant issues amongst the constituency of conservation professionals in Scotland relating to; dealing with a feature that has a lifelong history of failure, the underlying sub-structural issues that have arisen as a consequence, what constitutes original fabric on a house subject to a variety of repair approaches, and what seems an insurmountable problem coupled with the realisation that by not resolving this major issue impacts hugely on other aspects of the protected fabric, namely the interiors.
There are no clear answers but what has begun to emerge is a debate between two strands within the conservation world. On one side the fundamentalist 'do only the minimum' required to protect the integrity of the fabric. The other is a more expansive view that says in buildings of historic importance, their significance will inevitably be as a result of many aspects of importance, and that what is critical is to recognise that it may be necessary to differentiate the value of the various elements and qualities which constitute this heritage. In that process the ‘sacrifice’ of some less significant elements in the interest of preserving the long term integrity of others should be given serious consideration. Such a view is appropriately embedded in the recent ICOMOS Madrid Document 2011.
"Its cultural significance may rest in its tangible attributes, including physical location, design (for example, colour schemes), construction systems and technical equipment, fabric, aesthetic quality and use, and/or its tangible values, including historic, social, scientific or spiritual associations or creative genius."
So what are Andrew Wright’s tentative options presented for discussion? He has four, two on either side of the divide. On one side he suggests the most minimal intervention to preserve authentic fabric, together with a conservative approach to retaining what little original roughcast remains and the greater surface area of patch repair. In that respect, accepting that ongoing failure will continue to impact on the wider heritage with the associated 'firefighting' to protect that more widely affected fabric. On the other side he advocates the need to consider that we completely strip roughcast surfaces and re-apply them onto a solid background of either dried out masonry or indeed rebuilt fabric. He also goes further to consider wholesale replacement of roughcast to a significantly different specification onto a proprietary isolating system.
The context of any final decision has wide implications for the continued practice of conservation in Scotland's changing environmental context and we need to be alive and responsive to that context and the issues it raises, particularly on 20th century buildings, often with non-traditional materials and detailing.