CROSS Safety Report
Ceiling collapse in an educational building
This report is over 2 years old
A suspended ceiling in a large teaching hall collapsed days before the official opening of a new educational building.
Key Learning Outcomes
For the construction team:
Ceilings should be given the same degree of attention as the primary structure during both design and construction to improve safety, reliability and longevity
Selecting the correct fixings for the given environment and anticipated loads is important to ensure they perform as expected
Quality control and competent supervision on site can help to ensure that ceilings are built in accordance with the design
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A suspended ceiling in a large teaching hall collapsed days before the official opening of a new educational building (Figure 1). The opening ceremony was going to take place in the hall where the ceiling collapsed.
The teaching hall was under an external circulation area of the building, and at a late stage in the project there was concern over footfall sound impact affecting the space below. To overcome this problem, an acoustic ceiling was designed, and the contractor was instructed to install hangers in the slab for the suspension rods to support the acoustic ceiling.
On inspecting the failed structure, the reporter says that the contractor had procured correctly rated brackets, but had procured compression brackets as opposed to tension brackets. All of the brackets were overloaded, but just working, until one failed, which set off a chain reaction.
The reporter says that the reasons for the failure were:
Late changes which caused a risk
The specification for the acoustic ceiling was only partially complete
There was ignorance about the importance of the brackets
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This and other similar reports demonstrate a concerning trend of progressive collapse mechanisms in public buildings where there is a high probability of casualties in the event of failure. In each case, there has been a fault, or a combination of faults, in the design, selection or installation of fixings, and a lack of appreciation of the magnitude of the dead loads from acoustic ceilings. These would have been compounded because it is not usually possible to inspect the fixings after installation.
The danger of falling ceilings is not new. There is old cinematographic legislation that was brought in because of failures with lath and plaster ceiling fixings. The Home Office document ‘Recommendations on Safety in Cinemas 1955’, and which is still relevant says “Ceilings shall be in such a condition as not to cause a danger to persons visiting the premises”.
Ceilings shall be in such a condition as not to cause a danger to persons visiting the premises
There are other examples where the failure of a single component must not compromise the whole. For example, cable stayed bridges are designed so failure of one stay does not cause the bridge to collapse. Similarly what is needed for heavy ceilings is a robust design with a sensible appreciation by designers of the importance of what might appear to be trivial structural detail. There must be a sound design tracing load paths back to a solid platform with a responsible person in charge. It may be that guidance should be provided in Part A of the building regulations in a similar manner to the existing guidance on cladding systems.
CROSS has been concerned about fixings of various kinds for some time and these collapses illustrate very well the ‘3Ps’ promulgated by CROSS to illustrate the wide causes of failure:
Those involved exhibiting a lack of structural engineering competence such that the safety critical implications of the work were not recognised.
Lack of attention given to the procurement of the work and in particular to ensure that one competent party is responsible for the overall design. A failure to appreciate that these support systems are just as important as primary structural members. Lack of supervision and checking of installations.
Specification (or choice) of the wrong product i.e. not fit for purpose.
Fixing failures such as the 1981 Hyatt Hotel walkway collapse in which 114 people died demonstrate the magnitude of tragedies that can unfold.