Non-fragile roofing should be the standard specification for the canopy roof at any educational establishment where (unauthorised) access on to the glazing is a strong possibility.
This is obviously a big safety issue. There is a misconception that polycarbonate is strong so it will not break (which is basically true) but if multiwall or solid polycarbonate is not mechanically fixed into a glazing bar system it will simply pop out of the bars when put under pressure and in these circumstances the roof glazing will always be classified as fragile. The test for non-fragility is the ACR[M]001:2014. The Twinfix roof system passes this test with a class ‘B’ designation and full test certificates are available.
The following document outlines the information that supports the case of thermoplastics only receiving a class ‘B’ to the ACR (M):001:2014
In summary;
Taken from the ACR[M]001:2014 Test For Non-Fragility of Large Element Roofing Assemblies [fifth edition] the classification of ‘Class A’ is the following:
3.4.4 On conclusion of the second drop test, the load shall be removed and the assembly examined by the competent person and if, in his opinion, the roof sheet and the assembly shows no signs of significant damage that will affect the long term strength and weatherability of the assembly –see Note 6, the assembly may be classified as a Class A non-fragile assembly.
Note 6: Any tearing at the fixings, fractures in the sheet or the assembly support structure, delamination of the sheet or damage to the surface protection which could accelerate the degradation process should be seen as sufficient to withhold a Class A rating. See also paragraph 6.1
6.1 Designers need to recognise that most economic profiled roof assemblies will not achieve Class A rating. A Class B or Class C rating is perfectly acceptable for most roofing applications in terms of being deemed to satisfy Non Fragility when new. Class A ratings can possibly be achieved but the roof sheeting and fixings specification would need to be considerably improved and at considerable cost and generally for no additional benefit.
Therefore our stance on this is a classification of a class ‘A’ is not possible for the following reason:
The type of damage referred to above e.g fractures to sheet, support structure and surface protection may not be visible however the damage will still have been caused. Other company’s may take this as ‘no significant damage’ however as we understand thermoplastic roofing materials we know this damage could have occurred therefore we know that a Class ’A’ is not achievable. It is our standpoint that most “lightweight” roofing systems (pretty much anything other than concrete) will be unable to achieve a Class A rating, the maximum will be Class B.
Class A performance can only be achieved if there is no damage to the surface protection (which could accelerate degradation), which is extremely unlikely on any plastic material. This could only be verified by microscopic analysis if at all: any slight scuff, scratch or mark on the surface would damage the very thin surface protective layer and affect long term performance, preventing Class A classification.
We have consulted with NARM (National Association of Rooflight Manufacturers) and NARMs view on the ACR test is in agreement with para 6.1 In summary, all industry guidance, including that from the National Association of Rooflight Manufacturers, strongly recommends that Class A ratings should never be claimed for any rooflights, for the same reasons already outlined.
