Inspection and Maintenance of Fibrous Plaster Ceilings
All historic ceilings are at risk if not adequately maintained. Fibrous plaster ceilings can be complex in construction and require specialist skills for their inspection and maintenance. There is guidance available to help you determine the competency of specialist inspectors and contractors, and to define the required standard of inspection.
All theatres and places of entertainment with suspended fibrous plaster ceilings must have been inspected by a competent person by 1 September 2016 to ensure that they are safe.
The inspection must have complied with new survey standards devised by the Association of British Theatre Technicians (ABTT) and details of the survey requirements can be found in ABTT Guidance Note 20 on their website.
Many former places of entertainment with fibrous plaster ceilings are now in alternative use. However, fibrous plaster is not limited to theatres or places of entertainment. Therefore, the risk of failure is possible in any building with fibrous plaster ceilings with unstable hangers, ties and fixings, especially hessian wadding and fixings. The Health and Safety Executive (HSE) has informed all UK Local Authorities that this inspection scheme is in place in the theatre industry and that it can be applied to any building with a suspended fibrous plaster ceiling, as good practice.
The HSE states that: "If you have not managed to get your ceiling inspected within this period you are advised to contact your licensing authority (normally the appropriate Local Authority) to discuss how you can demonstrate that the ceiling is safe for an audience to sit beneath….Those responsible for premises with suspended plaster ceilings are strongly advised to read the ABTT guidance...."
Any queries about the required survey work for suspended plaster ceilings in theatres and places of entertainment should be directed to either Theatres Trust or the Association of British Theatre Technicians.
Historic England’s position
Historic England supports the application of the ABTT survey standards in any historic building with a fibrous plaster ceiling, both suspended and fixed. Fibrous plaster ceilings may be found in buildings of high status (commercial, administrative, cultural and residential) erected between 1856 (the date the material was patented) and about 1940. However, they may also be found as renovations/ restorations carried out within earlier structures, including post Second World War restorations. Many hundreds of them survive, sometimes undistinguished from traditional plaster and lath ceilings.
- These composite structures are often complex in design. Fibrous sections and panels consist of gypsum plaster reinforced with hessian, affixed to a timber frame through ties or hessian, and they may also have been reinforced. Heavy cast modelling is also common. Fibrous plaster may be suspended from a structure by means of metal and timber framework, or fixed directly onto structural substrates.
- Gypsum plaster and hessian are liable to degradation through natural ageing. These are also all weakened by moisture that makes hessian and timber susceptible to biological attack.
- Ceilings below roof structures are particularly vulnerable from water ingress, but those on lower levels of a building may also be affected by defective plumbing fixtures. Installation of sound systems in ceiling voids can also have an impact.
It is important to understand the risk and the necessity for proper inspection and repair. Failure to do so could result in a ceiling collapse, with serious or even fatal consequences.
Means of inspection
Where direct access to the ceiling void is lacking or limited, new access points will be required, and Historic England will give sympathetic consideration to any application for listed building consent for the creation of permanent access, subject to usual provisos:
- Every case will be considered on its own merits
- Any access holes or hatches must be as discreet as possible and the minimum needed
- Any major disturbance to provide platforms or supports should minimise disturbance to significant structures and surfaces
- Preference for access holes must be through areas of least architectural significance
- Access holes should not be designed to accommodate new ducting as well
Recommended procedures for identification, inspection and maintenance of fibrous plaster ceilings
Fibrous plaster and its fixtures should be surveyed by a competent plasterwork inspector and the structural parts supporting suspended fibrous plaster ceilings surveyed by a structural engineer experienced in such fabric.
The Association of British Theatre Technicians guidance sets out that a ceiling surveyor must:
- Compile and review existing building inspection and maintenance records (for example roof repairs / plumbing installation and repair records)
- Determine safe means of access to the ceiling void or other alternative means of inspection
- Identify the presence of fibrous plaster ceiling
- Establish general condition and integrity of the methods of attachment
- Record these conditions in written and graphic form; this becomes the baseline survey that is the foundation for later inspections
- Quantify the relative risk (for example vulnerability to water damage; weight of the ceiling and its constituents; the frequency of use of the room; the density of occupancy and the nature of activity)
- Recommend remedial repairs
- Advise as to the necessary timescales for follow up plaster and structural inspections
Repairs should be carried out and documented by a competent plasterwork contractor, followed by a robust maintenance regime. The ABTT guidance provides useful recommendations on these topics.
Guidance on establishing competence of inspectors and contractors
The FIS (Finishes and Interiors Sector) represents specialists in all aspects of the interior fit-out and finishes sector, including specialist plasterers. In conjunction with The Theatres Trust and the Association of British Theatre Technicians, the FIS has developed guidance on how to establish the competence of inspectors and plasterwork contractors. Inspection and repair of these complicated ceilings should never be entrusted to inexperienced contractors. There will be serious liability in the event of ceiling collapse and human injury.
These organisations have also produced a dedicated template for ceiling surveys, applicable to all fibrous plaster ceilings.
Historic England is undertaking a programme of research into the construction, deterioration, assessment, and conservation of fibrous plaster ceilings. The aim is to produce guidance on their care and maintenance.
Read more about the inspection of fibrous plaster ceilings: Inspecting historic fibrous plaster ceilings – article in volume 154 of Context, the Journal of the Institute of Historic Building Conservation, published by Cathedral Communications Ltd in May 2018.