Fibrous plaster degradation has been a key concern over recent years, with ceiling failures occurring suddenly in historic buildings, including the Apollo theatre in 2013. This rigorous investigation explores fibrous plaster degradation through subjecting 290 specimens to a range of moisture and fungal-related treatment conditions over periods of up to two years and analysis using mechanical flexural tests, Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Deoxyribonucleic Acid (DNA) sequencing. Using FTIR peak ratios from spectra of hessian fibres and mechanical tests in conjunction, an original methodology for identifying mechanisms and severity of fibrous plaster degradation through moisture and fungal exposure was developed. Results showed defined clusters for differing moisture and fungal treatments when two peak ratios are plotted together and compared with mechanical data. Fungal exposure over two years, water submersion and wetting and drying were particularly detrimental conditions for fibrous plaster. Fungal exposure resulted in degradation of cellulose bonds in hessian fibres, with defined clusters on the extreme left of peak ratio plots correlating with a pronounced reduction in fibrous plaster mean flexural strength of 51%. Fungal species Penicillium and Chaetomium were identified on test samples. Moisture affected plaster matrices significantly with wetting/drying and water submersion treatments resulting in a 71% reduction in mean flexural strength for unreinforced plaster, reducing to 26% with hessian-reinforced fibrous plaster. Many buildings containing fibrous plaster are listed and removal of material is often minimised - the high impact of this research stems from the ability to rapidly assess the mechanical integrity of a very small quantity of harvested historic hessian fibres using FTIR. Identifying the location of weakened fibres in a ceiling is highly important for effective restoration and conservation.
Original languageEnglish
Article number130604
JournalConstruction and Building Materials
Early online date9 Feb 2023
Publication statusPublished - 10 Mar 2023

Bibliographical note

Funding Information:
The authors gratefully acknowledge the funding of the Leverhulme Trust, grant number RPG-2021-147. The authors additionally thank the following for support and guidance:, The entire management and fibrous plaster teams at Hayles and Howe Ornamental Plasterwork and Scagliola, Bristol, United Kingdom for their time, resources and manufacture of the flexural test samples, plus the donation of historic fibrous plaster samples for laboratory analysis. Locker and Riley artisans in plaster, South Woodham Ferrers, Chelmsford, United Kingdom for donating historic fibrous plaster samples. Richard Ireland (historic decorative plaster and paint consultant, Plaster and Paint, United Kingdom). Scott Brookes (structural engineering consultant, Ramboll, United Kingdom). With thanks to the following: Berrak Balci (Researcher – flexural tests, Department of Architecture and Civil Engineering, University of Bath), William Bazeley and Neil Price (Technical support – flexural tests, Department of Architecture and Civil Engineering, University of Bath) and Philip J. Fletcher (SEM imaging and FTIR testing guidance and input, Department of MC2, University of Bath). The FTIR and Flexural test data for moisture and fungal degradation samples supporting this manuscript are available from the Dataset for the results of fibrous plaster tests, University of Bath Research Data Archive, https://doi.org/10.15125/BATH-01213.


  • Degradation
  • Deoxyribonucleic Acid (DNA)
  • Fibrous plaster
  • Fourier Transform Infrared Spectroscopy (FTIR)
  • Fungi
  • Hessian fibres
  • Moisture
  • Scanning Electron Microscope (SEM)

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Materials Science(all)


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