CROSS Safety Report
Partial collapse of suspended ceiling
This report is over 2 years old
A section of suspended ceiling in a multi-storey building collapsed.
Key Learning Outcomes
For civil and structural design engineers:
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
For the construction team:
Quality control and competent supervision on site can ensure the correct fixings are installed in accordance with the design
Fixings should be installed in accordance with the manufacturer’s specifications and requirements
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A section of suspended ceiling in a multi-storey building collapsed and it was fortunate that there were no injuries, says a reporter. The ceiling, which was much newer than the building, consisted of 1200 x 600mm mineral fibre tiles laid into a grid system supported by 2mm galvanised wires.
These were connected to eye bolts which were screwed into expansion anchors drilled into what appeared to be a plaster soffit. In the collapse area some of the expansion anchors had become detached from the soffit (Figure 1). The building was originally constructed using an early reinforced concrete floor system with hollow tiles, possibly clay based, between one way span in-situ ribs. The underside was then plastered.
Some anchor holes had been drilled into the plaster and the tiles but neither was a suitable substrate material. Other anchor holes were drilled into the concrete ribs but stopped short when reinforcement was hit. Whilst the building was old the ceiling had been in place for between 10 and 15 years. The reporter believes that the ceiling was inherently unstable and liable to failure at any time.
Expert Panel Comments
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This failure repeats yet again a pattern that has been observed in a significant number of incidents from the Boston Tunnel (USA) and the Japanese Sasago tunnel lining to various heavy ceiling collapses reported to CROSS.
There are two issues. Firstly, the potential for an anchor coming out for a number of reasons (a common one is putting them in too short). Secondly, and more widely, the possibility that any single failure will initiate a cascade type collapse. BS EN 13964-2004 is now the definitive standard for the manufacture and installation of suspended ceiling systems and applies in all countries of the EU.
It contains advice on selecting fixings appropriate to different substrates and should be used for new installations. BS 8539:2012 Code of practice for the selection and installation of post-installed anchors in concrete and masonry is the standard to use for fixings and guidance is also given in ‘Selection and installation of top fixings for suspended ceilings’ published by Association of Interior Specialists and the Construction Fixings Association in 2012.
Predicting whether an existing ceiling is safe is difficult but if there is any doubt then the fixings should be examined. CROSS will be issuing an alert on Tension Systems in the near future.
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