CROSS Safety Report
Swimming pool ceiling partial collapse
This report is over 2 years old
Overview
Part of a ceiling above a swimming pool collapsed, injuring four people. The ceiling had been installed approximately 12 years previously and showed no signs of distress before collapse.
Key Learning Outcomes
For construction professionals:
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Quality control and competent supervision on site can help to ensure that fixings are installed correctly and in accordance with the manufacturer’s requirements
For structural design engineers:
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Selecting the correct fixings and corrosion protection for the given environment is important to ensure they perform as expected
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The anticipated life span of the fixings should be noted in the operation and maintenance manual
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Designs should be robust enough to ensure failure of one fixing will not lead to the disproportionate collapse of the entire ceiling
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All loading conditions which may potentially exist should be considered and the appropriate products chosen accordingly
For building owners and managers:
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Regular inspections and maintenance can help keep a structure safe and identify any obvious safety issues that need to be addressed
Full Report
Find out more about the Full Report
The Full Report below has been submitted to CROSS and describes the reporter’s experience. The text has been edited for clarity and to ensure anonymity and confidentiality by removing any identifiable details. If you would like to know more about our secure reporting process or submit a report yourself, please visit the reporting to CROSS-UK page.
Part of a ceiling above a swimming pool collapsed, injuring four people, says a reporter. The ceiling was a double skin plasterboard false ceiling, supported off hangers which were screwed into timber joists above. The ceiling had been installed approximately 12 years previously and showed no signs of distress before collapse.
Upon investigation, it was found that the number of hangers was too few for the load and this resulted in failure of the hanger fixings into the joists. It was also found that the joists had twisted due to lack of noggins/strutting. A contributing factor may have been that the area above the ceiling was used as a gym, with potential for vibrations from dropped weights.
Although a structural engineer was involved, the design responsibility was with a specialist contractor. The ceiling was installed over a weekend, and there is no evidence of independent inspection. Building control was carried out by an approved inspector. No detailed drawings were produced, and the ceiling was not installed to manufacturer's standard details.
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Expert Panel Comments
Expert Panels comment on the reports we receive. They use their experience to help you understand what can be learned from the reports. If you would like to know more, please visit the CROSS-UK Expert Panels page.
This is one of many instances of collapse of ceilings above swimming pools- sometimes with fatal consequences. The problems (and the consequences) are now sufficiently well-known for all owners of such buildings to be aware of the need to carry out a structural assessment of the ceiling or roof.
Progressive failure
CROSS has received a number of reports of ceiling collapses and the typical form is a progressive collapse precipitated by a single hanger failure. You can search for safety information on ceilings on the CROSS website.
Such a failure might arise from a variety of causes but in a ceiling system, the distribution of load to any one hanger is fundamentally uncertain and could be significantly higher than assumed. It cannot be presumed that a tension system is ductile if the fixing of the hanger is the weak link. The location above a swimming pool suggests that corrosion or moisture degradation might also have been a contributory factor.
Failure due to stress corrosion
There have been several cases of ceiling failure over swimming pools with stainless steel hangers, brought about by stress corrosion. Often fixings are not appropriate for dynamic and quasi dynamic loading situations. In this case it appears that investigations concluded that the gym above was a source of vibrations which could have loosened some fixings and led to progressive collapse.
Designers need to be aware of all loading conditions which may potentially exist and choose appropriate products accordingly.