Fibrous ceilings – how can you identify and repair faults?
Fibrous ceilings are often a stunning piece of architecture, with intricate and complex designs. The unique ceilings are often associated with Victorian and Edwardian theatre and music halls; however, they are fitted in a wide range of buildings in the UK and beyond, with examples being found across a large number of heritage buildings.
Over time, the ceiling plaster may become damaged and begin to fail, with visible cracks and imperfections at best, and sections of the ceiling collapsing at worst. This degradation is often as a result of the deterioration of supporting structural reinforcements, such as hessian wadding or wooden laths.
Following the collapse of a ceiling in 2013 in the Apollo Theatre in London, building and health and safety professionals have recognised the need to review current practice throughout the industry and improve survey standards and competency requirements of fibrous plaster ceilings.
The result of this review was the introduction of the Advice to Theatre Owners and Managers Regarding Suspended Fibrous Plaster Ceilings, which necessitates regular inspections and the criteria for carrying out those inspections.
However, it’s important to recognise issues as soon as they arise to allow for remedial works to be carried out quickly.
So, what are the common issues in fibrous plaster ceilings and how can you identify them?
- Uneven ceilings – a fibrous plaster ceiling may appear to sag or bulge, with cracked finishes and bowed surfaces. In older buildings, plaster may sound hollow when tapped. This kind of damage is usually caused by the presence of moisture or damp in a ceiling, or where plasterboard sheets are not fully supported with reinforcements, meaning hessian wadding or wooden laths underneath may be decaying.
- Cracks in surface of plaster – small and irregular-shaped cracks and unevenness in the surface of plaster are signs of damage. Replastering may cover surface cracking, but the cracking may be caused by an internal issue within the ceiling, meaning cracks will reappear over time. It’s always best to consult a professional if you identify cracks in a ceiling.
- Mould and damp – recurrent damp and black mould growth can be an issue in buildings with fibrous plaster ceilings. It’s often a localised problem, caused by condensation forming on ceilings above cold spaces, generally as a result of poor insulation or a lack of ventilation.
Selecting the right materials for repair
When repairing a fibrous plaster ceiling or carrying out maintenance work, choosing the right material is crucial. The remedial material needs to bond well with the existing material, reducing the need for future maintenance work.
When choosing a material to use for repair work, testing for strength, compatibility and combustibility is key.
Case study – The Senate of Canada Building, Ottawa
In 2019, the ceiling of the Senate of Canada Building in Ottawa began to show signs of degradation and needed remedial work to repair.
“The coffered ceiling in the Canadian Senate Building and General Waiting Room, Ottawa, was originally made from traditional fibrous plaster – comprising plaster panels suspended from a metal frame,” says Joe Orsi, co-founder and building and materials consultant at Roman Products.
“The top side of the fibrous plaster had begun to show signs of ageing and there was uncertainty surrounding the stability of the hessian reinforcement of the gypsum cast.”
After two years of testing by government engineers in Canada, a mineral silicate product from Lime Green Products Ltd was chosen to carry out the conservation repair work.
The ceiling was repaired in situ, using a liquid penetrating primer to consolidate the friability of the historic plaster casting and give a chemically compatible surface for the adhesive. Then, a fibreglass mesh was fixed to the upper side of the ceiling using a mineral adhesive.
“This system has offered a sustainable and robust solution, which has safely repaired the 80ft high ceiling for the long-term,” says Joe.
How can you repair a damaged fibrous ceiling?
The repair works for a fibrous plaster ceiling will often involve reinforcement of the ceiling from above, by repairing or replacing wooden laths or hessian wadding and reinforcing the roof to ensure moisture isn’t present. This will help to prevent future rotting of the reinforcing materials.
Fundamentally, using materials that bond well with existing materials is key for maintaining and repairing a fibrous ceiling, to preserve the traditional characteristics and visually appealing nature of the design.
For more information, visit www.lime-green.co.uk or call 01952 728 611.