FIRE SAFETY | FAADES Figure 1: BS EN 1364-4 standard configuration 5 BSI Wall furnace preference to a more combustible alternative. The revised guidance will be soon be freely available on the CWCT website (www.cwct.co.uk). Further CWCT guidance The update described above is one part of a wider review of existing CWCT fire guidance. CWCT Technical Note 98, published in April 2017, is also being revised. In addition to reaction to fire, this technical note covers other key aspects of faade fire performance, including cavity barriers and firestopping. Reaction to fire While Regulation 7 provides new legal requirements for certain buildings (relevant buildings), the guidance related to other types of buildings is still a source of confusion and potential ambiguity. In terms of reaction to fire requirements, several interpretations are possible, which would influence the materials that meet the guidance in ADB (what is a filler material; which materials constitute the external surface; and so on). Reasoned argument and common sense are required to interpret the recommendations contained within ADB in such a way that a logical conclusion is reached that demonstrates compliance with the regulation. We are working with government to provide a consistent approach to applying the guidance. Compartmentation and curtain wall firestopping It is well established that firestopping is required between curtain walls and compartment walls and floors. Such firestopping should provide the same period of fire resistance as the floor or wall to which it abuts. However, curtain walls are not generally required to be fire-resisting, 42 July 2023 www.cibsejournal.com Figure 2: Protected spandrel Siderise The exemptions do not fully recognise the complexity of modern faades and leave some ambiguity and uncertainty over combustible materials and research carried out by the Loss Prevention Council (LPC) showed that failure of curtain walls in fire could occur within 15 minutes, potentially allowing fire to bypass any firestopping. This, together with a lack of specific test methods for curtain wall firestops and limited guidance in ADB, has resulted in the use of firestops that have been tested between rigid materials with little consideration of the effect of the curtain wall on the performance of the firestop. The need to review the fire safety of faades following the Grenfell Tower fire along with the development of standard test procedures for curtain wall firestops and the focus on satisfying the functional requirements of the Building Regulations, rather than merely following ADB guidance requires a reappraisal of established practice. A number of approaches to testing firestops have been used in the past, including ad hoc tests based on the principles of BS 476, BS EN 1366-4 and, more recently, BS EN 1364-4. It is proposed that references to testing in accordance with BS 476 be dropped from ADB, thereby removing the option for ad hoc testing following the principles of BS 476. Such tests generally involve testing the firestop between rigid fire-resisting materials, so are unlikely to represent the performance in conjunction with a curtain wall. BS EN 1366-4 has been used for testing curtain wall firestops. However, it was amended in 2021 to exclude perimeter seals of curtain walling from its scope. BS EN 1364-4 gives a method of testing curtain wall firestops that can be applied to curtain walls that are not fire-resisting, although fire protection of the inner face of the curtain wall in the