The Non-Fragile topic is of great importance nowadays as everyone becomes more aware of the health and safety issues on building sites and the need to safeguard people working there.
Safety concerns with rooflights - the Non-Fragile issue
Whilst recognising that achieving natural daylight in buildings through the use of rooflights is important, falls through fragile roofs and rooflights has been identified as one of the main causes of numerous deaths and thousands of injuries that have occurred in the construction industry over the years. The statistics were sufficiently alarming for the Construction Division of the Health & Safety Executive (HSE) to single out fragile roofs for a priority programme in 2004/5.
Rooflights are a particularly obvious element of a roof assembly that should be able to support the instantaneous loads imposed by persons stumbling or falling onto them.
The HSE are extremely keen to have non-fragile assemblies specified for installation on roofs, especially in buildings that are considered to be at risk from vandals/intruders who find their way on to the roof.
However, there is sometimes a misunderstanding regarding the safety of people on roofs. Some specifiers think that by requesting a roof glazing system that conforms to BS6206 then they are providing a safe rooflight. This is not the case.
The HSE Document HSG33 outlined the Health & Safety recommended testing method ACR[M]001:2019 ‘Test for Non-Fragility of Profiled Sheeting Roofing Assemblies’. The ACR[M] drop test is far more onerous than BS 6206 as it represents a human impact incident on a roof surface where a fall through (the glazing) might result in death or serious injury, whereas BS 6206 was designed for vertical low level glazing where the main objective is to prevent human injury from broken glass.
ACR[M]001:2019 is a test of an assembly rather than a product. Rooflights are not tested alone, but as part of a representative roof assembly and it is the whole assembly which achieves non-fragility.
The Advisory Committee for Roofwork, led by the Health & Safety Executive, undertook research that led to the development of the above test, which represents a human impact incident on a roof surface.
The pass categories than can be achieved with the ACR[M] test are shown below:
- 'A' is the highest rating and is achieved only if there is no visible or significant damage to the whole assembly after multiple drops.
- The 'B' classification is based on minimal damage caused by multiple drops.
- A 'C' graded pass requires only one drop test with the impactor.
The Twinfix Multi-Link-Panel NF
The Multi-Link-Panel NF (Non-Fragile) combines a maintenance-free aluminium frame fitted with virtually unbreakable polycarbonate glazing, either multiwall or solid.
Many years ago we build a test rig in accordance with the HSE’s requirements and we regularly assess our Multi-Link-Panel NF products to the ACR[M] test. Every Multi-Link-Panel NF polycarbonate option we offer has achieved a 'B' pass rating.
In addition, we have tested 16mm multiwall polycarbonate fitted into one of our own glazing bar systems. This failed the test, with the multiwall sheet simply popping out of the 60mm wide glazing bars. This demonstrates the wisdom of the HSE requirement to carry out the test on 'assemblies' and not on individual components.
We have also tested 6.8mm laminated glass. It failed, with the 45kg impactor bag crashing straight through the glazing, leaving a huge hole.
HSE Drop Test Videos
Please click on the link below to see the HSE drop tests carried out on a range of relevant products.
- 6mm solid polycarbonate glazed in the Twinfix Multi-Link-Panel NF - passes the test with a B classification and can therefore be designated as 'non fragile'
- 16mm multiwall polycarbonate glazed in the Twinfix Multi-Link-Panel NF - also passes the test with a B classification and achieves the 'non-fragile' designation
- 16mm multiwall polycarbonate glazed into a 60mm wide glazing bar - fails the test and is therefore designated as 'fragile'. This video shows why the HSE say that the test is to be carried out on 'roofing assemblies' and not on individual components: it is the patented system within the Twinfix Multi-Link-Panel NF that enables it to achieve the B classification and 'non fragile' designation.
- 6.8mm laminated glass glazed into standard glazing bars - fails the test and is therefore designated as 'fragile'
The CDM regulations state that designers must:
“when carrying out design work, avoid foreseeable risks to those involved in the construction and future use of the structure. In doing so, they should eliminate hazards (so far as is reasonably practicable, taking account of other design considerations) and reduce risk associated with those hazards which remain”
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