30
floors, walls & ceilings
ceiling specification
that holds up
Ceiling collapse is not unprecedented, sadly nor is it actually that infrequent.
Here, technical manager for AIS, Joe Cilia, explains why it happens and what can be done
to avoid this costly and potentially life-threatening risk. ..
While providing independent advice during the investigation
of various ceiling collapse incidents, AIS has identified ten
common reasons for ceiling failure. Most prominent of these
are the fixings. Where these are incorrectly specified, poorly
installed or simply due to an insufficient number of fixings
being used, a ceiling is prone to failure.
and any future changes. What material the ceiling is being
hung from is also a crucial piece of information. Finally, any
environmental factors - moisture from a corrosive atmosphere
such as a swimming pool for example, or buildings subject to
particular structural vibration - must be considered in order to
specify the optimum fixings, according to the application.
Critical to the safety and security of a suspended ceiling
and its associated equipment are the top fixings. BSEN
Next, the structural integrity ofthe proposed specification
needs to be checked; will it take the load of the ceiling and
anything else to be suspended from it, now and in the future?
Will the fixing carry the load? Finally, a preliminary test is
needed where there is no European Technical Assessment
in place to provide data on the recommended load in the
substrate to rule out any doubt. It is important for the
specifier to remember that, even where correct fixings are
used, there may still be instances where a ceiling fails and
the fixings are found to be the cause of the problem,
due to incorrect installation, or incorrect size.
13964:2004
Suspended ceilings - Requirements
and Test
Methods states that "the type and number of top fixings shall
be specified;' and "the selection of top fixing method shall be
detailed on the relevant drawings': However, it is very rare
that the top fixings are specified.
Without this specification as is so often the case, the installer
or specialist contractor is left to select the fixings they feel
are most appropriate for the application, without fully
understanding the parameters of the project or installation
requirements. The architect or designer is best placed to
advise and specify the fixings, based on their knowledge of
the applied load, the base material into which the top fixing
is to be installed and any other environmental factors that
might impact on the ceiling or fixing after its installation.
The Best Practice Guide to the Installation
of
Top Fixings for Suspended Ceilings from
AIS, in conjunction with the
Construction Fixings Association
provides recommendations
on the selection process.
These include the importance
of identifying the applied load
- both the current loading
Continued on page 32....
32
floors, walls & ceilings
... Continued from page 30
Issues can be avoided by following the manufacturer's
instructions for both the ceiling system and the fixings
themselves. Equally, following trades may implement
modifications that, in time, could compromise the
specification and safety of the ceiling. For example,
suspension wires or hangers might be cut or removed
to make space for new services. In the worst examples,
these services are suspended from an existing fixing that
already has to support the ceiling. In other instances,
hangers are replaced with inappropriate substitutes,
such as cable ties, that just don't stand up to the job.
Tbe weight applied to a ceiling is an important factor.
Access to the ceiling void should ideally be carried out with
the help of a competent ceiling installer because tiles need to
be removed correctly from the exposed and concealed grids.
Some systems call for specialist tools to remove the tiles not screwdrivers and an element of brute force, which can
damage the pips holding the tiles in place, ultimately leading
to possible partial ceiling collapse. Equally, excess loading can
be applied
as a result
of wires
laying on
the tiles, cable trays, ductwork, lighting, air handling units,
signage and other accessories. Such components must be
supported independently of the ceiling system itself.
Ceiling failure and top fixing failure can be the result
of structural vibration. Structural vibration can cause
the anchors holding the ceiling to weaken, eventually leading
to collapse. The education environment is one in which
structural vibration can occur. One case where heavy carts
were regularly pushed over an uneven exposed floor caused
enough vibration to result in ceiling fixing failure.
The substitution of a ceiling component that has been
specified by the architect or designer for another component
can have disastrous consequences. Its compliance with the
required standards - and any manufacturer's warrantyis drastically compromised and even voided.
Knowledge and training are the keys to the accurate
specification and safe installation of a suspended ceiling.
Not only should these components be selected by a competent
person, they should also be installed by a competent person
who understands the requirements. A specialist contractor who
is a member of a specialist trade association will have accessto
the right knowledge and training.
CM270
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