Many culturally important historic buildings contain fibrous plaster ceilings. The collapse at London’s Apollo Theatre in 2013, which injured 88 people, highlighted the importance of inspecting and restoring ceilings effectively. This study focuses on traditional and modern materials which are applied to the topsides of existing historic fibrous plaster ceiling elements during repair and maintenance. Fibrous plaster ceilings are commonly suspended from primary or secondary structural roof members using fibrous plaster wadding ties or ‘wads’. The application of additional repair material requires the formation of an interface, defining the strength of the repair. Properties of this interface were evaluated through a novel methodology employing pull-off tests’ of approximately 200 specimens consisting of Alpha plaster, Beta plaster, Jesmonite and Aramid gel. Notably, the effect of fibrous reinforcement, and compatibility with historic and degraded material was also investigated. This study has enabled quantification of interfacial properties and evaluated cohesive and adhesive failure modes. Importantly, the extent of redundancy within historic plaster ceiling practice has been demonstrated, with pull-off occurring from 0.5 kN to 2 kN loading, and the ductile behaviour of repair materials evaluated. Results highlight the importance of surface condition, with clean surfaces exhibiting double the tensile loading capacity compared to soiled (dirty) surfaces representative of those encountered on-site. The significance of this study lies in the quantification of repair material performances and consideration of variations in performance, methodology and in-situ environmental factors. Impact stems from the ability of practitioners to make informed decisions relating to adhesion performance when carrying out repairs. A key outcome is more effective preservation of historic elements in heritage buildings, higher levels of safety and serviceability.

Original languageEnglish
Article number149
JournalMaterials and Structures
Issue number8
Publication statusPublished - 13 Sept 2023

Bibliographical note

Funders: Leverhulme Trust [Grant number RPG-2021-147]; CREST [Grant number 877766384]; and Historic England

Acknowledgement (including data access statement):
The authors gratefully acknowledge support from the Leverhulme Trust through Grant Number RPG-2021-147, Historic England and the Climate-Resilient Energy Secure and healthy built environments (CREST) project. CREST is supported by a Going Global Partnerships—Collaborative Grant from the British Council’s Going Global Partnerships programme [Grant Number 877766384]. The authors would also like to express their gratitude to the following companies for generously contributing time and materials for this research: Hayles and Howe Ornamental Plasterwork and Scagliola Ltd., Bristol, United Kingdom, with additional thanks to Robin Harrison for sharing expertise and arranging visits to theatre venues in the United Kingdom to view surveying and repair work. Locker and Riley Artisans in Plaster, South Woodham Ferrers, Chelmsford, United Kingdom, with additional thanks to Gary Buckley for sharing expertise. Historic Plaster Conservation Services Ltd., Port Hope, Ontario, Canada, with thanks to Rod Stewart, Eric Stewart and Masumi Suzuki for the image in Figure 1 f. Ornate Plaster (London) Ltd., Farnham, Surrey, United Kingdom. The authors additionally thank Richard Ireland, Plaster & Paint: Consultancy & Conservation of Historic Buildings, UK for the use of the image in Figure 1 e. Thanks also goes to William Bazeley and Neil Price within the Department of Architecture and Civil Engineering, University of Bath, for providing technical support during this study. The individual pull-off test data supporting this manuscript is available from the dataset for the results of fibrous plaster tests contained in the University of Bath Research Data Archive with the reference https://doi.org/10.15125/BATH-01275


  • Adhesive failure
  • Adhesive tests
  • Cohesive failure
  • Fibrous plaster ceilings
  • Interface
  • Pull-off strength

ASJC Scopus subject areas

  • Mechanics of Materials
  • General Materials Science
  • Building and Construction
  • Civil and Structural Engineering


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