Specifications for Building Conservation

Volume 1: External Structure

Rory Cullen, Rick Meier, Rory Cullen, Rick Meier

• Editore: Routledge
• Anno: 2017
• ISBN:
  9781317427698
• Edizione: 1
• Argomento: Architecture
• Categoria: Historic Preservation in Architecture

In Specifications for Building Conservation, the National Trust draws on a range of case studies and specifications to provide a much needed guide to specification writing for building conservation. Although traditional building accounts for approximately a quarter of all buildings in the UK, the old skills and understanding required for their care and maintenance have been increasingly eroded over the last century. As the largest heritage charity in Europe, the National Trust has a first class reputation for high standards of conservation and care, and in this three volume set, the Trust brings together a remarkable pool of expertise to guide conservation professionals and students through the process of successful specification writing.

This first book focusses on the materials used for the external fabric, detailing successful approaches employed by the National Trust at some of their most culturally significant sites. A range of studies have been carefully selected for their interest, diversity and practicality; showcasing projects from stonework repairs on the magnificent Grade I listed Hardwick Hall to the re-thatching of the traditional cottages of the Holnicote Estate.

Complete with a practical Conservation Management Plan checklist, this book will enable practitioners to develop their skills, allowing them to make informed decisions when working on a range of project types. This is the first practical guide to specification writing for building conservation and the advice provided by the National Trust experts will be of interest to any practitioners and students involved in building conservation, both in the UK and beyond.

Profits generated from the sale of this publication will go to the National Trust Building Apprenticeship Scheme. This provides placements for traditional skills at National Trust properties.

Part 1
Conservation philosophy and principles

The philosophy and principles encompass the reasons for the work and desired outcome. The philosophy is the sum of the factors which drive the need for undertaking building works; these will be predominantly conservation based for historic buildings, but might include physical, commercial, environmental or other drivers in different works. The principles embedded within a project set out the need for appropriate research and ensure that significance is recognised, understood and respected.

Conservation Philosophy

A clearly defined brief needs to be drawn up prior to writing a specification, following survey and investigative works. This will describe the conservation philosophy being adopted, whether repair, maintenance, conservation, restoration and/or adaptation.

• Repair: work beyond the scope of maintenance to remedy defects caused by decay, damage or use. Includes minor adaptation to achieve a sustainable outcome, but does not involve restoration or alteration.
• Maintenance: routine work which is often necessary to keep the building fabric in good order.
• Conservation: the process of managing change to a significant place and its setting in ways that will best sustain its heritage values, whilst recognising opportunities to reveal or reinforce those values for present and future generations.
• Restoration: returning a site to a known earlier state, on the basis of compelling evidence, without conjecture.
• Adaptation: use of appropriate additions and/or alterations to secure the future use and viability of a historic building.

The philosophy should provide a clear framework demonstrating how decisions about physical interventions in the fabric of the building will be made, and the basis on which these should be undertaken.

The introduction to each of the case studies sets out the context for the work by describing the conservation philosophy adopted. This helps to ensure an appropriate and sensitive approach which preserves the historic fabric, enabling repair and conservation rather than restoration.

Conservation Principles of Heritage Organisations

The specific driver for any works to historic or vernacular buildings, irrespective of listed status or function, should be the significance of the fabric itself.

The National Trust has maintenance strategies and policies to protect and enhance the physical estate. To the Trust, 'conservation' is the careful management of change. It is about revealing and sharing the significance of places and ensuring that their special qualities are protected, enhanced, enjoyed and understood by present and future generations. The driving force behind how it manages this is set out in these conservation principles.

• Significance: we will ensure that all decisions are informed by an appropriate level of understanding of the significance and 'spirit of place' of each of our properties, and why we and others value them.
• Integration: we will take an integrated approach to the conservation of natural and cultural heritage, reconciling the full spectrum of interests involved.
• Change: we will anticipate and work with change that affects our conservation interests, embracing, accommodating or adapting where appropriate, and mitigating, preventing or opposing where there is a potential adverse impact.
• Access and engagement: we will conserve natural and cultural heritage to enable sustainable access and engagement for the benefit of society, gaining the support of the widest range of people by promoting understanding, enjoyment and participation in our work.
• Skills and partnership: we will develop our skills and experience in partnership with others to promote and improve the conservation of natural and cultural heritage now and for the future.
• Accountability: we will be transparent and accountable by recording our decisions and sharing knowledge to enable the best conservation decisions to be taken both today and by future generations.

The Society for the Protection of Ancient Buildings (SPAB) was founded by William Morris and other notable members of the Pre-Raphaelite Brotherhood in 1877 to oppose what they saw as insensitive renovation of ancient buildings in Victorian England. Today the SPAB still operates according to Morris's original manifesto. Its principles are:

Repair not restore: although no building can withstand decay, neglect and depredation entirely, neither can aesthetic judgement nor archaeological proof justify the reproduction of worn or missing parts. Only as a practical expedient on a small scale can a case for restoration be argued.

Under the Planning Acts, the SPAB must be notified of all applications in England and Wales to demolish in whole or part any listed building; this includes ecclesiastical buildings which are normally outside the planning process.

The Burra Charter defines the basic principles and procedures to be followed in the conservation of Australian places. As the Charter observes: 'conservation is based on respect for existing fabric, use, associations and meanings'. It also emphasises the importance of the fabric in understanding the site:

The traces of additions, alterations and earlier treatments to the fabric of a place are evidence of its history and uses which may be part of its significance ... the cultural significance of a place is embodied in its fabric, its setting and its contents' – that is, the 'historic building itself is an artefact'.

The International Council on Monuments and Sites (ICOMOS) defines its conservation principles as:

Imbued with a message from the past, the historic monuments of generations of people remain to the present day as living witnesses of their age-old traditions. People are becoming more and more conscious of the unity of human values and regard ancient monuments as a common heritage. The common responsibility to safeguard them for future generations is recognized. It is our duty to hand them on in the full richness of their authenticity. (International Charter for the Conservation and Restoration of Monuments and Sites, 'The Venice Charter', 1964)

Historic England is the government's statutory adviser on England's historic environment. It is responsible for assessing buildings for listing and puts forward its recommendations to the Secretary of State for Culture, Media and Sport who makes the final decision. The actual management of listed buildings consent applications and approval of these is the responsibility of local planning authorities.

Historic England's six key conservation principles are as follows.

1. The historic environment is a shared resource.
2. Everyone should be able to participate in sustaining the historic environment.
3. Understanding the significance of places is vital.
4. Significant places should be managed to sustain their values.
5. Decisions about change must be reasonable, transparent and consistent.
6. Documenting and learning from decisions is essential.

A charity, the English Heritage Trust is licenced to care for and open to the public the National Heritage Collection of more than 400 state-owned historic sites and monuments across England. There is some overlap with the Trust's portfolio, but they do not have the farmed estates or tenanted properties the Trust has responsibility for.

Equivalent organisations to Historic England and the English Heritage Trust in the other home countries are:

• Cadw in Wales
• Historic Scotland
• The Northern Ireland Environment Agency.

Consideration of conservation principles

Conservation principles should be set out to ensure that conservation work to a historic building shows the greatest respect for its historic fabric and overall cultural heritage value. It should be achieved with minimum intervention and involve the least possible loss of historic fabric.

Preventive conservation, in the form of regular monitoring and maintenance, is the key tool in conserving historic properties. Early identification of deterioration enables it to be slowed or stopped, thus avoiding unnecessary repairs. Regular maintenance is preferable to repair, and timely and effective repair is preferable to restoration. It follows in conservation 'best practice' that when repairs, additions and alterations are made to historic buildings and structures, these should be handled 'truthfully' to make clear what is original fabric and what is new (introduced) fabric.

For example, in carrying out repointing to brickwork, ageing or distressing the new mortar should normally be avoided in preference to allowing natural processes to blend the new work with the existing over time. Modern analysis can be used to establish the mix and colour of sand to match existing materials.

An important consideration when the works include alterations is 'reversibility', i.e. that they are capable of being reversed so that the site can return to its previous state.

From a financial perspective, finding a new use may be the only effective way of retaining a building. The basis of judging the most appropriate alternative use is likely to relate to least interference with the fabric, and therefore only those uses which reduce or avoid interference should be acceptable. For example, the sympathetic reuse of a disused historic farm building or barn for light industry could be achieved by inserting a whole new 'standalone' structure, which requires minimal connection, within the historic farm building 'shell'. In this way, hygienic linings could be applied to the new structure without affecting original surfaces and minimal fixings to the original structure. These new insertions could be easily reversed in the future. Conversely, adaptation of that building to a residential dwelling would usually be a last resort as it would typically require significant intrusive alterations to the historic structure, which could be difficult to reverse.

Buildings should have a viable use to ensure their environmental and financial sustainability. The issue of reducing energy is an ethical matter related to the greater social good of reducing impacts on the environment. This is a careful balance between environmental impact and the conservation and social value of the built cultural heritage.

The issue of the embodied energy in the existing building and its energy consumption should also be considered. Embodied energy is the energy and carbon consumed on manufacturing of building materials and building construction, including the transport in connection with these activities. It is therefore essential that there is a detailed understanding of the actual energy performance of the building and, irrespective of statutory compliance, that there is an acceptance of the building's limitations and energy 'trade-offs'.

A key principle should be to understand what you have, how it works, what you need and how to use less energy more effectively. The materials used in pre-1919 buildings allowed the fabric to 'breathe', whereas modern materials insulate; failure to understand traditional building processes and their interaction with modern technologies could cause damp problems and irreversible damage. Before preparing specifications for work that includes energy efficiency measures, consider the existing energy performance of the building; for example, when specifying repairs to a window frame, detail sympathetic draught-proofing measures or secondary glazing.

Implementation of the principles

A thorough survey and understanding of a building's construction and the materials used is essential before undertaking any works. How comprehensive these are will depend upon the building's significance, usually stemming from its listed status, the works proposed and the time of year. Outcomes of surveys should include:

• a drawn, scaled record giving floor plans, elevations and cross-sections and/or long sections where needed
• a fully indexed digital photographic record to support the drawings
• an analysis and interpretation of the development of different periods of the historic building
• an analysis of the form and character of the building and where appropriate of its landscape character in the locality and setting
• identification of inappropriate materials used in previous maintenance that may affect the long-term structural integrity of the building
• a description of the building's construction and materials
• prioritisation of repairs and, where scaffolding is necessary, identification of all essential repairs so that this can be undertaken whilst the scaffold is in place.

Conservation Plan

The principles can be put into practical steps in a conservation plan. This is a holistic document, drawing together research which will lead to thorough understanding of the asset's significance. This will then inform any discussion concerning the building which will ensure appropriate decisions are taken.

The plan should be structured and include an array of information relating to the history and construction of the asset. This is achieved through detailed building recording. The document also explores the cultural significance of the asset. It may also contain the long-term vision and detail regimes by which it can be maintained or conserved. The conservation plan will present valuable information to those responsible for the building's conservation or alteration. It will also assist with the design and justification of any necessary works which require statutory consent, aiding the progress of an application.

Heritage Legislation

Statutory legislation exists to protect the environment in which we live; to ensure that built structures are fit for purpose and to reduce the r...