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CROSS Safety Report

Incorrectly fixed sheets blow off parapet

Report ID: 1180 Published: 25 May 2023 Region: CROSS-UK


Overview

This report concerns aluminium coping sheets that blew off the parapet of a block of flats under construction. The reporter says a fierce wind blew off several of these sheets which fell to the ground about 9m below. A building and a car were damaged but thankfully no one was hurt, although the potential for personal injury or death was significant.

Key Learning Outcomes

For architects, engineers and other specifiers:

  • Give attention to the whole design of parapet capping and other small sheeted systems, including the safety-critical aspects of their fixings and anchors

For construction product manufacturers:

  • Provide clear and unambiguous product instructions, illustrated with diagrams as necessary
  • Streamline the number and type of fixings that are used and ensure installation procedures are similar

For builders, main contractors and sub-contractors:

  • Adequate quality assurance and competent supervision helps to ensure that systems are installed in accordance with the design
  • Care must be taken to ensure that parapet capping and other small sheeted systems are always fully fixed as per the manufacturer’s requirements
  • Where small sheeted systems are only partly fixed, ensure they are safe in the temporary condition
  • Where complex sheeted systems are being installed, it is good practice that specific training for installation is provided

Full Report

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This report concerns aluminium coping sheets that blew off the parapet of a small block of flats under construction. The reporter says a fierce wind blew off several sheets which fell to the ground about 9m below. A building and a car were damaged but thankfully no one was hurt. The site was next to a public car park, a highway, and office and residential buildings, so the potential for personal injury or death was significant.

The reporter says it appeared that the copings were fixed a few days earlier and were clipped on the outside edge over the fixing plates as stated in the manufacturer's instructions, but the operative failed to attach the inside edge by screw fixings. The reporter understands that the wind lifted them from the unfixed inside face.

The reporter believes this was a communication failure as these copings were different from those that the contractor had used in the past, from the same manufacturer, which were clipped both front and back to their fixings. The site operative may have assumed that these were intended to be fixed in the same way. Alternatively, the operative may have put them in place and intended to fix them the next day.

The reporter is concerned that these copings may have been supplied without clear instructions which the reporter contends are very important when the same supplier offers a range of systems with different fixing methods.

Expert Panel Comments

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An Expert Panel 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-US Expert Panel page.

The importance of fixings and correct installation methods are often overlooked at a site level. It doesn't matter how good the product is if it is not adequately fixed.

Anything that presents a significant wind area will rely on adequate connection around its entire perimeter to remain safe and secure. If only some fixings are installed, they will be loaded in an unintended manner and potentially fail, as appears to be the case here.

If only some fixings are installed, they will be loaded in an unintended manner and potentially fail

The incident shared by the reporter focuses on the omission of some of the fixings for a panel, but it is often also important that all the panels in a system are installed. A free edge can lead to a temporary wind loading condition not envisaged by the designer of the system.

It is imperative that operatives understand and are instructed on how parapet systems, or indeed all other systems, are to be installed. As suggested by the reporter, following what the operative did on the last project may be insufficient and result in a failure. Specific training for a system is imperative, especially if the operatives are part of the general site labour rather than specialists.

To enable adequate fixing there must of course be total clarity of manufacturer's instructions, with all fixing details for all cases and products explained clearly.

there must be total clarity of manufacturer's instructions, with fixing details for all cases and products explained clearly

Finally, quality assurance requirements should allow for every element of the works to be independently verified as having been installed correctly. Site supervisors should also be mindful of the state of completion of the works at all times, particularly before work on any element finishes for the day.

CROSS has reported on a number of failures to panels and sheets which happened during high winds including  CROSS-UK report 1172 - Cladding failure in strong winds and report 1134 - Metal cladding panels fail and fall to ground.

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