Conservation is the stewardship of our built heritage. Buildings cannot be made to last forever but with good conservation they will survive as long as possible, suffer the least alteration and enrich society the most.
However, the world must move on, and realising the potential of development sites while conserving our built heritage often creates conflicts of interest between developers and conservationists.
In 1994, PPG 15 set out the government's policies for historic buildings and conservation areas in England.
1From December 2003, English Heritage and the Heritage Lottery Fund will only grant-aid projects if the lead professional is accredited in conservation. Historic Scotland will follow suit in April. This stipulation only affects projects requiring funding from these two bodies. For schemes grant-aided by others, or privately funded schemes, non-accredited architects can carry on as normal.
Currently, PPG 15 sets out the criteria for judging the conservation merit of a building. They include its age, interest (architectural, structural and historical), context, rarity, intrinsic originality, structural condition and economic viability. But it is a double-edged sword. If a building fails these tests then it is fair game for developers to apply for consent to demolish it, although they will also have to demonstrate the replacement building will be of greater benefit.
Accreditation scheme assessments are based on five units developed under a Historic Scotland commission 3from the 1993 International Council on Monuments and Sites (ICOMOS) Education and Training Guidelines:
l unit 1 - cultural significance;
l unit 2 - aesthetic qualities and value;
l unit 3 - investigation, materials and technology;
l unit 4 - social and financial issues;
l unit 5 - implementation and management of conservation works.
For the average practitioner, unit 3 is at the heart of the practicalities of conservation. It has six tenets:
l minimum intervention;
l conserving as found;
l using like-for-like materials;
l honest repairs;
l sympathetic repairs;
l reversible alterations.
One test of good conservation is achieving as many of the above maxims as possible, while recognising that a low score does not necessarily mean bad conservation.Unlike 'traditional' buildings, the structures of many 20th-century buildings were designed with one eye on efficiency of materials and this can cause consternation. For example, at a listed 1930s residential building in south London the misguided search to make the thin cantilevered walkways comply with modern-day structural standards almost led to these important elements being replaced.
A working knowledge of conservation can help unlock projects by resolving planning stalemates, by harnessing the professional teamwork between conservation architects and engineers, archaeologists and planners. However, given that there are only 150 accredited architects working in this field in the UK, one can understand that, according to some grant-funding agencies, there is a dearth of endorsable skills.
Building services engineers are conspicuous by their absence from the accreditation scene, despite the regular need to insert modern services in old buildings often causing damage to the historic fabric.
The debate continues The work at Aylesford Priory (see box) is a singular example of just one facet of conservation. Most issues cannot be similarly quantified and must be resolved by negotiation and good old compromise. There are usually many issues to consider:
l Should traditional materials and techniques always be used, even if modern equivalents give better results (for example, stainless steel masonry bed-joint reinforcement, instead of Victorian hoop-iron)?
l Should work be blended or distinguished from original fabric (for example, tile-creasing infill of eroded masonry, instead of new stone)?
l Should we repair and consolidate rather than renew, even if durability is uncertain (for example, 'plastic' repairs to external masonry)?
l Should we retain as much existing material as possible, even if it has lost its surface finish and will accelerate the decay of other parts (for example, loss of projecting drips)?
l Fabric must be replaced when structurally unsound, but should we wait until it is on the brink or replace it sometime beforehand to be confident of an increased lifespan and also so that the need for continued maintenance access is reduced; saving time and money in the long run.
These are all important questions for which there are no easy, nor 'correct' or 'incorrect', answers. The merits of each case must be weighed up and the pros and cons assessed in terms of what the overall objective is and what the possibilities are. Very often negotiation and consensual resolution are key.
What is conservation?
Conservation is not preservation, renovation, refurbishment, facade retention or rebuilding facsimiles, but most conservation projects include an element of these allied approaches. It applies to all sorts of historical works and sites, be they bridges, piers, canals, railways, military and industrial sites, or natural landscapes.
Conservation can range in scale from craft processes for the piecemeal repair of vernacular fabric such as cob walls or medieval timber frames, through to the adaptive reuse of large engineered structures such as warehouses and bus garages. Along the way, gems can be discovered and saved, and unworthy examples culled.
Conservation is promoted worldwide by the United Nations Educational, Scientific and Cultural Organization (UNESCO) and ICOMOS, who raise the awareness of conservation issues with governments.
At a national level, central and local government use the planning system, together with the amenity societies the Society for the Protection of Ancient Buildings (SPAB), the Georgian Group, the Victorian Society and the Twentieth Century Society, who are statutory consultees.
Works and sites designated to be conserved include World Heritage sites, scheduled monuments, listed buildings, locally listed buildings, and other buildings that have sufficient merit, particularly those in conservation areas.Some sites have multiple designations.
The Department for Culture, Media and Sport is currently reviewing the statutes that produce this plethora of designations. Its consultation paper Protecting our Historic Environment: Making the System Work Better (the consultation period of which has just closed) acknowledges that the present system is now so complex that few people fully understand all of it.
All sorts of buildings of all ages, including those of the latter half of the 20th century, can be worthy of conservation.Given sufficient time and money, even the most decrepit buildings can usually be conserved. But should they be saved?
CASE STUDY AYLESFORD PRIORY, KENT Within Aylesford Priory stands Pilgrims Hall, a Grade II-listed timber-framed three-storey refectory from around 1440.The hall was built on the banks of the River Medway and its superstructure was leaning progressively away from the river.All parties agreed that buttresses were necessary but disagreed on their position.The friars and its architects, Thomas Ford & Partners, preferred external buttresses, English Heritage preferred internal buttresses problem (counterforts), while another option was to hide them within the 900mm-thick rubble-cored ragstone wall.
The position of the buttresses had to be agreed before listed building consent could be granted.To break the impasse, the conservation solution criteria were listed that were important to all the interested parties, allowing an assessment of how well each buttress position would satisfy the criteria.The result, which favoured external buttresses, was accepted by all parties.
Propping up the margins Existing structures need adequate margins of strength, stability and integrity to survive for a defined life span, but they do not always need to comply with the current British Standards or Eurocodes. After all, you cannot always identify an old building that has been told in a design code that it should fall down.
Nevertheless, as time goes by we inevitably learn more about the weaknesses of old structures. For example, last year the Standing Committee on Structural Safety (SCOSS) issued a national safety warning about 19th-century cast-iron beams carrying jack-arch roofs, after a sudden collapse at Grade II-listed Hyde Park Gardens, London, 2002.
Intervention is only necessary when structural defects have eroded the margins of safety perilously close to failure or are likely to do so within the defined lifespan. Judging what is an adequate margin of safety, or whether structural defects are a serious threat, requires the customary surveying and engineering skills.
Professional institutions vary in their support and local authorities have a shortage of conservation officers. Postgraduate courses have only modest uptake, while first degrees are only available for new structures.
Those of us who know anything have mostly acquired our skills on the job.
Those skills are ever changing. So a passion for old buildings and consensus politics are the key to success.
Clive Richardson is a visiting lecturer in conservation at the Architectural Association and technical director of Cameron Taylor Bedford. Email:
clive. richardson@camerontaylor. co. uk References 1The Department of the Environment Planning and Policy Guidance Note 15, 'PPG 15: Planning and the Historic Environment'.HMSO,1994.
2Conservation-led Regeneration.English Heritage, November 1998.
3A Framework Description of Competence for a Shared Approach to Built Environment Conservation Accreditation Schemes in the UK.Historic Scotland et al, 2002.
FURTHER READING Richardson, C, 'The Dating Game' (AJ 23.3.00) Richardson, C, 'Moving Structures' (AJ 14.9.00) Richardson, C, The AJ Guide to Structural Surveys, The Architectural Press,1986.
Skills of a conservation architect Essential for a conservation architect is a good knowledge of construction history: learning how materials, components and systems vary through the ages will open up the vocabulary of a building. If you don't know how a building is put together, how can you possibly understand why it is coming apart?
Also essential is a full understanding of the seven generic causes of structural movement:
linadequate strength of materials;
l inadequate continuity (togetherness) between components;
l material decay;
l dimensional instability (thermal/moisture expansion and contraction);
l subsoil/foundation inadequacies;
l overall instability; and l alteration, accidents and misuse.
A conservation architect must be able to read a building with minimal opening-up, to avoid damaging historic finishes.To do this you can use historical desk studies, measured surveys, visual structural surveys, movement monitoring or non-destructive testing.
You must also exercise restraint.Resist the temptation to leave your mark on history; always sit on your hands unless it is absolutely necessary to intervene.
Finally, don't be afraid to use modern materials, components and techniques if they best serve the maxims of conservation.