Responsibility for testing internal glazing and doorsets in flexible supporting structures now lies with the manufacturer. James Parlour, FIS Technical and Vetting Manager, discusses the pitfalls and solutions.
The newly published FIS guide ‘Walls as a system’ highlights the importance of fire resistance having compatible and compliant test evidence between elements of construction. One such case of this is where internal, non-loadbearing glazed partitions, doorsets, and windows are installed into an opening formed in a flexible supporting construction namely, drylined lightweight steel frame partitions. It is crucial to point out that whilst the drylining partition manufacturer should warrant that a specified flexible wall type wall can still perform to robustness standards with often large openings formed, they cannot test or underwrite the fire resistance performance of these openings . This means that responsibility for testing internal glazing and doorsets into flexible supporting structures lies with the manufacturer of the supported element, i.e. the doorset or glazed partition manufacturer.
What is a “standard flexible supporting construction”
The terms “supporting construction” comes from the EN fire testing standards, principally in the example of glazing and doorsets:
• BS EN 1364-1 Fire resistance tests for non-loadbearing elements – Walls
• BS EN 1634-1 Fire resistance and smoke control tests for door and shutter assemblies, openable windows, and elements of building hardware – Fire resistance test for door and shutter assemblies and openable windows
• BS EN 1363-1 Fire resistance tests – General requirements Both BS EN 1364-1 and BS EN 1634-1 refer to the general requirements in BS EN 1363-1 and state that when a test specimen is smaller than the test frame, a rigid or flexible standard supporting construction given in BS EN 1363-1 should be provided. Flexible standard supporting constructions relate to lightweight steel framed drywall partitions and are specified in BS EN 1363-1 as shown in Table 1. Responsibility for testing internal glazing and doorsets in flexible supporting structures now lies with the manufacturer. James Parlour, FIS Technical and Vetting Manager, discusses the pitfalls and solutions.
The following commentary is also given:
• A result of a test undertaken with a construction in accordance with Group A covers studs in Groups A, B and C.
• A result of a test undertaken with a construction in accordance with Group B covers studs in Group B and C.
• A result of a test undertaken with a construction in accordance with group C covers studs in Group C only.
This gives a rationale for manufacturers to test their products into flexible supporting constructions using the most onerous configuration without having to test every possible permutation of stud, board thickness, number of boards, and type of insulation combined, then duplicate this for each manufacturer of drywall systems. It is important to note however that if a test specimen is mounted in a non-standard supporting construction (also called an associated supporting construction), then the result will only be valid exactly as tested.
Where are the pitfalls?
The rationale behind the EN testing methodology can fail to deliver its utility in several ways. First, if test evidence is gathered using the BS 476-22 methodology, the EN testing rationale does not apply and the manufacturer must evidence compatibility with a variety of wall configurations using another method. Second, it is often unclear to designers and specifiers when a fire performing drywall specification is also a standard supporting construction as defined by BS EN 1363-1, and when these are not specified or are value engineered out of the wall types schedule, compatibility of test evidence can be compromised, for example by installing a type A plasterboard in lieu of a type F board. Finally, it is often unavoidable to test elements in non-standard supporting constructions because standard supporting constructions either do not adequately describe common wall types required in the market, such as asymmetric or twin-frame configurations, or cannot accommodate significant weights of doors and glazing within the openings or carry detailing in the linings for the embedment of specified fixings.
The solution
The solution to this issue lies in collaboration and early engagement. When drywall partitions are performing as a supporting construction, standard constructions detailed in BS EN 1363-1 should be specified whenever possible, and their removal from a specification through value engineering should be resisted unless the product manufacturer has demonstrated upfront that the systems have been tested together. Specifying one of these wall types adds considerable value to the design development process, as the likelihood of compatibility of evidence is higher. Designers must also be mindful of the challenges related to the compatibility of evidence and must ask more detailed questions of the manufacturer regarding issues such as the construction of reveals, and any variations to the standard construction. Similarly, manufacturers of glazing and doorsets need to present test evidence for their products so that it clearly communicates the variety of supporting structures that have been tested including whether they are standard constructions in accordance with the EN testing rationale.
