Track 2: Materials over Time: Points of Change

General Abstract

1 - Conserving Bowing Marble Cladding

Monday, September 24
2:45 PM - 4:15 PM
Location: BNCC- 101BG

The phenomenon of bowing Carrara marble cladding on 20thC buildings is now well-known. Bowing of the marble panels leading to replacement, on such prominent buildings such as the 80 storey Amoco Oil building in Chicago, and Alvar Aalto’s Finlandia Hall in Helsinki, have been significant contributors to this awareness.

Understanding of the drivers for this bowing phenomenon has been achieved through detailed research over the past forty years. As a consequence, the historical precedents to address the bowing phenomenon have reflected the prevailing understanding, and have thus been of their time. Whilst the primary driver is now considered to be a thermal hysteresis mechanism, and standard methods to assess the potential for bowing to occur in marble from specific quarry sources have been developed, options to address the bowing marble cladding already on buildings are still evolving. This partially arises from gaps in knowledge about the interactions between bowing marble panels and the fixings with which they are installed.

Driven by a variety of reasons, the generally accepted solution to the problem has been to replace the marble cladding – mostly with another material (e.g. Amoco Oil building), or occasionally, where the marble cladding has been considered an integral component of the architecture, with new panels of marble fabricated and/or installed in a different way (e.g. Finlandia Hall). This is, of course, a valid response, particularly when the apparent risks to public safety, and the changes in appearance associated with bowing, are taken into account. Nevertheless, the removal of all of the original marble cladding, and replacement with a different cladding system, can have a substantial impact on the heritage significance of these buildings.

This presentation presents the findings of research into the array of alternative responses which can be considered when bowing of Carrara marble cladding occurs on buildings considered to have heritage significance, particularly where the marble cladding itself is a contributor to the heritage significance. It draws on a range of examples within Australia, the United States, and Europe.

This presentation seeks to establish a baseline for evaluation of appropriate actions from the time that bowing is first detected in the marble cladding. It describes a range of conservation actions – both preventive and interventive – which have the potential to extend the life of the bowing marble cladding. Existing research, examples and unpublished feedback will be considered, and potential conservation actions which merit more detailed research will be identified.

Learning Objectives:

David West

Executive Director
International Conservation Services

A materials scientist with extensive experience in the use of stone in building, particularly as cladding, David West consults to the building industry through Materialswise. David is also a director of International Conservation Services, Australia’s largest private fine arts and heritage conservation business. He has been an active member of ASTM Committee C18 on Dimension Stone for over 30 years, and is co-convenor of the APT Australasia Chapter, as well as a past Board member of APT International. Throughout his career, David has combined hands-on testing and evaluation of a wide range of dimension stones; the detailing of new stone cladding systems; and the condition assessment, and diagnosis of deterioration, of stone installations on both modern and historic buildings. He has particular interests in the deterioration mechanisms of sandstone, the bowing of marble cladding, and the long-term behaviour of cladding systems.


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Lorraine Schnabel

Schnabel Conservation LLC

Lorraine Schnabel is the principal and owner of Schnabel Conservation LLC, a full service materials conservation consulting firm. We work with preservation project teams to diagnose whole building and individual material deterioration problems and identify workable, practical, durable solutions. After nearly thirty years in practice as both a private conservator and as a project manager at John Milner Associates and 1:1:6 Technologies, Lorraine has developed experience with most types of building materials and historic construction systems. Her principle areas of expertise are masonry and materials analysis. She has applied her skills in the preservation of a broad range of building ages and types, from small historic houses to the Baltimore Washington Monument. Currently, she is co-chair of the APT Technical Committee for Materials, and she has served on the board of the Delaware Valley chapter of APT as well. She is a Fellow of the American Institute for Conservation of Historic and Artistic works, and served in leadership roles in the Architecture Specialty Group and Conservators in Private Practice of that organization. She teaches Building Conservation to students in the College of Architecture and the Built Environment at Jefferson (formerly Philadelphia) University. Lorraine holds a BA in Geology from Pomona College and an MSc. in Historic Preservation from Columbia University.


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1 - Conserving Bowing Marble Cladding

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