CROSS Safety Report
Dangerous glass infill panels on balustrade
This report is over 2 years old
A reporter has expressed their concern about the structural stability of cantilever glass infill panels between a steel post and handrail balustrade system at a high-level apartment block.
Key Learning Outcomes
For civil and structural design engineers:
Where specialist systems such as glass infill panels are used, it is beneficial to have a close working relationship with the supplier from the earliest opportunity to ensure design requirements are met
Glazing design is often carried out by a specialist contractor. If the glazing is to withstand horizontal loading this requirement should be conveyed to the contractor
Careful consideration should be given to cantilever glass barriers to ensure they are adequately fixed at the base
If you are involved in the design of balustrades / barriers with glass infill panels, it is good practice to consult:
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A reporter expressed the following concerns about the structural stability of cantilever glass infill panels between a steel post and handrail balustrade system at a high-level apartment block:
The glass infill panels are set into a mastic filled channel at the base which in places is deteriorating
Some infill panels are laminated, and some are non-laminated
The steel post and handrail balustrade system is not connected to the glass infill panels
According to the reporter, in the event of a failure at the base, there is no secondary fixity to prevent complete failure of the glass sheet (Figure 1). The height of the apartment means that patio furniture can get blown right round three sides of the block of flats by wind. In the event of impact from the furniture, the non-laminated glass could shatter.
Remedial works on glass infill panels
The reporter feels that all the non-laminated sheets of glass need to be replaced with laminated glass. They feel a secondary top fixing bar in stainless steel should be added to exploit the existing post and rail system. This would hold the top of all the glass sheets given what appears to be the deterioration of the single base fixing. Remedial work was undertaken to fix the top edges of the glass sheets to the posts, on flats with the same detail (Figure 2).
Expert Panel Comments
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Safety at height is a major concern and should always be in the forefront of the mind of a designer of external components in tall structures.
Here, the glass simply cantilevers from a mastic filled channel at the base, which is not a robust detail, and does not provide safety either for residents or passers-by.
Safety concerns of glass cantilever panels
Cantilevers always require care and glass cantilevers particularly so. The risk is that if the glass breaks from impact then; firstly, there would be a large gap below the balustrade rail though which someone could fall and, secondly glass shards or granules could fall on the ground below. Another possibility would be that a panel was dislodged outwards, without breaking, but with the same consequences.
Industry guidance on glazing
Small changes to the design would have resulted in a much safer scenario and substantially reduced the risk. The usual procedure for a designer would be to consult The Centre for Windows and Cladding Technology (CWCT) standards and guidelines for glazing, and the Construction Industry Research and Information Association (CIRIA) Guide to Glazing at Height C632F.
Small changes to the design would have resulted in a much safer scenario and substantially reduced the risk
Glass is a specialist material that fails in a sudden fashion and any bespoke application should always be designed by someone with appropriate knowledge and experience. There should be discussion at the design stage to satisfy the requirements of CDM Regulations 2015 and to deal with residual risks.
There are a number of CROSS reports about balconies and glazing. You can search for safety information on balconies and glazing on the CROSS website.
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