Track 2: Materials over Time: Points of Change
1 - Conserving Bowing Marble Cladding
Monday, September 24
2:45 PM - 4:15 PM
Location: BNCC- 101BG
International Conservation Services
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.
- Upon completion, participants will be able to: describe the history of understanding of the causes of bowing marble cladding on buildings.
- Upon completion, participants will be able to: describe the challenges to the conservation of heritage significance of marble cladding on modern buildings where the marble cladding is bowing.
- Upon completion, participants will be able to: list a range of alternative options for conservation of bowing marble cladding on modern buildings.
- Upon completion, participants will be able to: discuss future research needs that could lead to more refined approaches to the conservation of bowing marble cladding on modern buildings.