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INTER IORS
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deteriorated leaving an ‘empty egg shell’
of plaster. Further intrusive investigation
is required to ascertain stability.
PRESERVATION OF FIBROUS PLASTER
The findings of the Association of British
Theatre Technicians (ABTT) inquiry will be
felt in more than 300 listed theatres around
the UK according to The Theatres Trust,
whose director Mhora Samuel noted:
Many of these ceilings will also have
been strengthened with wire ties and,
as a result, will be very secure. A full
nationwide survey will be needed
to establish the number of theatres
affected including unlisted theatres.
Those constructed from the mid-19th
century to before the second world war
will be particularly affected.
In March 2014 the ABTT established a panel
of 38 experts including specialist plasterers,
structural engineers, acousticians, health
and safety experts, architects and key
industry organisations. Historic England
(then part of English Heritage), the Health &
Safety Executive and the Building Research
Establishment were involved from the outset
so it was clear that their findings would have
a great deal of influence. The Theatres Trust,
founded in 1976, also became involved in an
advisory capacity.
Defining the true nature of suspended
fibrous plaster ceilings was an initial priority
and the panel concluded that there are
two distinct parts: the plasterwork and the
framework, each of which should be securely
fastened to the other as well as to the building
structure itself. This led to a first principle:
All ceilings should be inspected by two
competent persons, one expert in the
condition of the structure (a structural
engineer) and the other an expert
in the condition of the plasterwork
(a plaster surveyor or a plaster
contractor familiar with the inspection
of heritage buildings).
Determining the competence of the inspectors
was a key priority for the ABTT. While
structural engineers have relatively clear-cut
qualification criteria, the same cannot be said
of plasterers, often artisans with extensive
on-the-job experience but little in the way of
widely accepted accreditation of competence.
There is just a handful of specialist
plastering firms nationwide with the
knowledge and expertise to carry out this
kind of sensitive investigation. A formal
qualification may be in the offing for
fibrous plastering but nothing comes close
to the practical knowledge gained from
working on historic buildings. Theatres are
therefore advised to ‘undertake independent
assessments of the competence of plaster
specialists’ (ABTT Guidance Note 20, see
Further Information).
The second principle proposed by ABTT
involves ceiling inspections taking place,
from both above and below, to ensure the
integrity of the attachments. Any specialist
plastering firm will know that inspections
from above can be very difficult to carry
out. Often relying on the construction
of inspection hatches, many of these
investigations have to take place from a
distance and the importance of ensuring
these ceiling areas remain free of debris and
the build up of dust cannot be taken lightly.
Theatre owners on the ABTT panel were
consulted about this major consideration
and practical methods established to make
‘above’ inspections far more accessible.
This is where the experience of an expert
plasterer really comes into its own. In the
short term, theatres where inspections
from above cannot be carried out,
should seek to mitigate any risk of falling
plasterwork with the erection of netting.
The ABTT also concluded that
pyrotechnics and acoustics, when managed
and delivered effectively, have no negative
effect on the fibrous plaster in a theatre despite
the ever-growing power of sound systems.
The overarching and immediate priority,
however, is for theatre owners to find out
whether unreinforced wadding ties form part
of their suspended ceilings with steps taken
to strengthen the ties ‘as soon as is reasonably
practicable’ if it is proven to be the case.
Of course, it’s not just theatres which
have suspended ceilings. There are thought
to be hundreds of public heritage buildings
around the UK for which the ABTT findings
are equally relevant and we should be mindful
that these venues are also at risk.
In May 2015, almost 18 months after the
Apollo Theatre ceiling collapse and following
a year-long investigation, the ABTT published
guidance on how to inspect, certify and
record the condition of suspended fibrous
plaster ceilings (see Further Information). The
procedures outlined in the guidance are being
trialled by the Society of London Theatre.
The comprehensive guidance has drawn on
the experience of many experts and therefore
carries much weight and influence.
It is predicted that the cost of the
recommended inspection checks could come
in at around £15 million, or £15,000 for every
theatre – a tough ask for organisations that
are frequently sailing financially close to
the wind. However, if we are to avoid the
kind of scenario played out at the Apollo
Theatre in December 2013, then the ABTT
recommendations need to be applied in full.
It is a small price to pay to ensure that stage
productions around the UK can continue to
securely and safely ‘raise the roof’.
Further Information
The Association of British Theatre
Technicians, ABTT Guidance Note 20:
Suspended Fibrous Plaster Ceilings, London,
2015 )
The Finishes and Interiors Sector,
(FIS unites previous
organisations the Association of Interior
Specialists and the Federation of Plastering
and Drywall Contractors)
D Harrison, ‘Dramatic Plasterwork:
Fibrous Plaster in Theatres’, The Building
Conservation Directory, Cathedral
Communications, Tisbury, 1999
WMillar, Plastering: Plain and Decorative ,
(1897), Donhead, Shaftesbury, 1998
RONNIE CLIFFORD set up Ornate Interiors
(see page 167) in 1988 and has over three
decades of experience in traditional
plastering at many architectural landmarks
across the UK and Europe. His Leeds-based
business has collected many awards over
the years including the coveted Plaisterers’
Award, the highest accolade in the industry.
The back of a suspended fibrous plaster ceiling showing the hessian and plaster ceiling ties or ‘waddings’ which
bind the ceiling to the fixings above it
New ceiling ties with reinforcing wire