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Journal of Architectural Conservation

Volume 12 Number 1 March 2006

Editorial
Bob Kindred MBE

What are the processes by which conservation practices change? When does a proposition or principle become received wisdom? Management of some aspects of the historic environment is marked by specific events. Occasionally the formulation of a charter or standard will define common ground around which a consensus will then coalesce. Landmark legal decisions may redefine the accepted meaning of words and phrases or how they are applied, to the extent that heritage practitioners must immediately change their procedures, interpretations or behaviour.

In other arenas, change is sometimes so gradual that the profoundness of the change is apparent only in retrospect, not being marked by any single significant or discernible step, but brought about through the quiet, patient, empirical evolution of soundly based research. 

Dealing with the evolutionary and empirical first, the University of Bath group of Mike Lawrence, Dr Peter Walker and Dr Dina D'Ayala highlight the initial findings of a study of the Non-Hydraulic Lime Mortars: The Influence of Binder and Filler Type on Early Strength Development. The research forms part of the long and gradual retreat by the heritage sector back to traditional mortars from what had once been the unquestioning acceptance of the superiority of cement-based mortars.

Continued incremental development is also evident in the use of laser technology in conservation. The last Journal issue explored its use in cleaning, while in this edition, David Barber, Ross Dallas and Jon Mills set out the basis and practical application of both the hardware and software for Laser Scanning for Architectural Conservation. Ross Dallas had previously identified the potential while the technique was in its relative infancy, in a paper in 2003, but as with all emerging technology, the appropriateness of the application must be determined at the outset if reasonable expectations are to be fulfilled and the momentum of further use maintained.

For many UK practitioners the initials 'APT' will mean the Association of Preservation Trusts, the umbrella organization for the building preservation trust movement. These 'repairers of last resort', now nearly 300 strong, are often at the cutting edge of community-led heritage regeneration. Others in conservation will know APT as The Association for Preservation Technology, a pre-eminent organization of professional conservation in North America. It has grown from a small information exchange network in 1968 to a core membership of 1,500 professionals; its structure, activities, special interest groups, publications, newsletters and peer-reviewed journal - the respected APT Bulletin - are described by Hugh Miller.

Do practitioners too easily forget that the past was once the future? Instead of perceiving yesterday on its own terms, they fall into the trap of viewing it from today's perspective. Frank Matero's wide-ranging paper Loss, Compensation and Authenticity in Architectural Conservation reviews in particular the nineteenth- and early twentieth-century concepts of conservation in terms of the aesthetic implications of intervention in the processes of natural decay. He examines the ways in which past ideas about preservation and consolidation impinge upon current considerations of weathering, patina and the idea, not to say ideal, of completeness.

In Western society views of heritage exhibit a continuous thread from the Enlightenment to the present, and a background of rationality and Eurocentricity. UNESCO's World Heritage List, although ostensibly an expression of universal cultural values, is notable in this, in its preservationist ethos and in the regional bias of its designations.

Recent papers, however, notably that by Seung-Jin Chung in 2005, made explicit a markedly different and equally valid set of values - political, cultural and religious - underpinning architectural conservation, where a tradition of continuous intervention and renewal has been expected.

Formulating principles for heritage conservation based on this fundamentally different cultural and social model, with a distinct historical background and building tradition, but related to long-established international norms, has been the recent challenge facing China. Considerable progress has been made in ways applicable to the particular circumstances of China's heritage, mindful of its eternal susceptibility to geophysical disruption as well as its architectural expression. Dina D'Ayala and Hui Wang's paper, Structural Preservation of Chinese Architectural Heritage: A Critical Appraisal of the China Principles and the Structures Principles, speculates on the significant impact of these two important documents. First promoted in 2000 and 2003 respectively, they are expected to have profound repercussions for historic building conservation practice in China. As the Principles are adopted, a debate will need to be initiated on better education and training if they are to be successfully applied. There will have to be more detailed guidance on their practical application and appropriate technical and practical skills must be nurtured. A recognition that such a debate is required, and that meeting such requirements will be a challenge, is one not confined to China and will have universal application.

The Influence of Binder and Filler Type on Early Strength Development

Mike Lawrence, Peter Walker and Dina D'Ayala

Lime-based mortars are now widely acknowledged as generally superior to cement-based mortars in the repair of appropriate historic infrastructure. Increasingly the benefits of hydraulic lime mortars are also being realized in new masonry construction. In order to standardize the expected performance of mortars, designers will specify the type of lime, the type of filler (aggregate), the proportions of each and quantity of water or the required workability. Limes can be non-hydraulic (calcium or dolomitic) or hydraulic (natural or artificial). This paper reports on results of tests conducted on non-hydraulic lime conservation repair mortars at early stages of curing. Results to date show that the type of both non-hydraulic lime and filler used have a significant effect on the early (up to 28 days) mechanical performance of a lime mortar. The mortars in the study were made using five non-hydraulic lime binders: dry hydrate; 4 month-old lime putty; 20 year-old lime putty; 'hot' lime; and dispersed hydrated lime. The fillers were silicate sand, crushed bioclastic limestone, and crushed oolitic limestone. No pozzolanic material was added to the mortars. Compressive strengths at 14 days ranged from 0.3 MPa to 2.5 MPa. Comparisons are made between the structural performance and rates of carbonation up to 28 days of each binder:aggregate combination. In conclusion, observations are made on factors to be considered when specifying non-hydraulic lime mortar mixes for repair work.

R. M. H. Lawrence MSc, MA, FCMA.

Mike Lawrence offers a consultancy service diagnosing diseases to stone and advising on suitable treatments. He is currently working towards a PhD studying conservation repair mortars at the University of Bath where he obtained an MSc in the Conservation of Historic Buildings in 2003. He is managing director of Conservation Consultants (Worldwide) Ltd and of The Ham Hill Stone Company, which extracts and processes Ham Hill stone. (www.cc-w.co.uk)

Peter Walker, BSc, PhD, MIEAust, CPEng 

Dr Peter Walker is senior lecturer in Civil Engineering in the Department of Architecture and Civil Engineering at the University of Bath. He teaches structures and materials technology, and specializes in research on sustainable construction materials, in particular lime and clay-based materials.

Dina D'Ayala. Dr.-Ing, PhD

Dr Dina D'Ayala is senior lecturer in the Department of Architecture and Civil Engineering at the University of Bath, where she has lectured on structures, conservation of historic buildings and earthquake engineering since 1996. She has a first degree and a doctorate in structural engineering from Universita di Roma La Sapienza in Italy, and is an expert in structural conservation and earthquake protection of historic structures and urban settlements.

David M. Barber, Ross W. A. Dallas and Jon P. Mills

Laser scanning has, over the past five years, become a technique of interest to those undertaking or requiring architectural measured surveys for archaeology, architectural conservation, and documentation of historic buildings. Variously called 3D or terrestrial laser scanning, the technique provides an interesting opportunity to augment existing recording and measurement methods and offers new ways of displaying and presenting spatial relationships. This paper outlines the technique and examines its application in architectural conservation, and includes a selection of examples that illustrate its use. Finally, it provides a summary intended to help users understand when and how laser scanning could be used.

David M. Barber PhD, BSc

David Barber is a research associate at the University of Newcastle specializing in the use of terrestrial laser scanning and photogrammetry in a wide range of engineering and heritage-related problems.

Ross W. A. Dallas BSc, FRICS

Ross Dallas provides a specialist consultancy service in all aspects of the measured survey and recording of historic buildings. Prior to this, he was Chief Surveyor of English Heritage Survey Services for several years.  

Jon P. Mills PhD, BSc, MRICS MInstCES

Jon Mills is a senior lecturer in geomatics at the University of Newcastle with research and teaching interests in photogrammetry and laser scanning. He has been teaching techniques for close range measurement for over seven years and has also undertaken a number of related research projects, including the assessment of low-cost desktop digital photogrammetric software packages for English Heritage.

A Critical Appraisal of the China Principles and the Structures Principles

Dina D'Ayala and Hui Wang

Two documents issued by the International Council on Monuments and Sites (ICOMOS), The Principles for the Analysis, Conservation and Structural Restoration of Architectural Heritage (Structures Principles), 2003, and The Principles for Conservation of Heritage in China (China Principles), published in 2002 and formally promoted in 2005, will impact greatly on historic building conservation practice in China. To date, the approach to intervention on historic buildings in China, which can be summarized as 'no change to originality', has been strongly determined by both the fabric of Chinese architecture and customary Chinese engineering practice. The China Principles integrates traditional intervention philosophy with up-to-date international concepts on conservation, and provides a practical guidance for preservation activities in China. However, the increased involvement of structural engineers in heritage work since the 1980s has led to the promotion of the Structures Principles, which aids a systematic approach to the structural diagnosis and analysis of a historic building. This paper discusses how the aspects addressed in the Structures Principles and the China Principles could be assimilated into Chinese architectural heritage conservation. The paper also outlines the absence in both documents of guidelines for some specific issues concerning intervention strategies, diversity of heritage categories and specific materials, and finally identifies areas for further work.

Dina D'Ayala Dr.-Ing., PhD

Dina D'Ayala is a senior lecturer and director of Postgraduate Studies in the Department of Architecture and Civil Engineering, University of Bath. A member of ICOMOS-UK, she is currently chairing the national ISCARSAH committee. She teaches structural engineering and heritage conservation, with main research interests in seismic vulnerability and historic building conservation. She has worked on World Heritage sites such as the Colosseum in Rome, Lalitpur Nepal, Jerash Jordan, and Gondar Ethiopia.

Hui Wang BE

Hui Wang is currently an MPhil student at the University of Bath and a senior engineer in Hebei Provincial Administration of Cultural Heritage, China, a member of ICOMOS China. He was involved in the China Principles application case study programme (Shuxiang Temple Conservation Projects in Chengde), which is conducted by the State Administration for Cultural Heritage in China and the Getty Conservation Institute in the United States of America. His current research focuses on multi-hazard vulnerability appraisal of historic buildings.

Frank Matero

Not lost but gone before - Seneca, Epistoloe 63, 16

Loss and compensation have been central issues in the conservation of art and architecture at least since the sixteenth century as described by Vasari. In modern conservation practice, the term 'compensation' is now used to include all aspects of intervention designed to address visual and structural reintegration resulting from material loss. They are inextricably tied to conservation's primary objective, the protection of cultural resources from damage and depletion. Their consideration reveals much about past and present notions of cultural heritage including its meaning and significance across time, and the interventions that have been employed for its preservation and presentation. Discussions of material loss and its remedy, compensation, ultimately confront the larger questions concerning all artistic and historic works: authenticity, artistic intent, and value. For the student and experienced professional alike, issues of material loss and degradation and the oft-stated requirement of structural and visual reintegration can be among the most difficult problems encountered in conservation regardless of whether the work is a painting, sculpture, tapestry, or building. In considering such fundamental issues as loss and compensation, we bring conservation as a discipline, increasingly defined and separated by its specializations, back together to consider its essential and unifying issues and tenets.

Frank G. Matero BA, MSc

Frank G. Matero is professor of architecture, chairman of the Graduate Program in Historic Preservation, and director of the Architectural Conservation Laboratory, University of Pennsylvania. He was formerly assistant professor and director of the Center for Preservation Research at Columbia University (1981-90), and architectural conservator for the National Park Service (1979-81).

Profile of a North American Conservation Organization

Hugh C. Miller

The Association for Preservation Technology, known by its logo as APT, has been for 38 years the premier membership organization combining the dissemination of scholarly studies of the history of building with discussions about the application of the philosophy and practice of heritage conservation technology. This profile describes APT's programmes, its conferences and training courses as dynamic exchanges of ideas among practitioners, programme managers and policy makers. Also discussed are the APT publications, newsletters and peer-reviewed journal, the APT Bulletin. These are international in their scope and the entire collection is available to members online. The Association's special place in the field of conservation both in North America and internationally is described. Readers are encouraged to become familiar with the APT literature and the APT membership benefits.

Hugh C. Miller FAIA, FAPT

Hugh C. Miller is an adjunct professor at Goucher College where he teaches preservation technology and directs the writing of theses for the Masters of Arts in Historic Preservation program. He served 28 years in the National Park Service and was Chief Historical Architect for the National Park Service from 1979 to 1988. He has been an active member of APT since 1972, serving on their Board of Directors where he directed the publications programme. He is now a member of the APT College of Fellows.

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