voestalpine Metsec has been recently involved with BRE for detailed testing of party wall/SFS wall junctions to strengthen fire safety assurances.
IN MODERN LIGHT STEEL FRAMING, designers have long understood how individual wall systems perform under fire exposure. What has been missing, however, is clear evidence of how these systems behave where they meet. The junction between a party wall and an SFS external wall is a critical detail that, until now, has depended on engineering judgement. voestalpine Metsec’s latest full-scale fire testing addresses this longstanding knowledge gap directly.
A critical detail, historically untested
Standard methods such as BS EN 1364-1:2015 provide established benchmarks for isolated wall performance. They do not, however, address real world construction interfaces. As a result, design teams have traditionally relied on conservative assumptions when assessing the fire performance of internal wall to external wall junctions. These assumptions have been safe, but untested.
Testing what designers actually build
During summer 2025 at the BRE, two large scale test specimens were constructed to replicate common party wall/SFS wall junctions, tested following the general principles of BS EN 1364-1:2015. These were not abstract laboratory setups, they were representative of real site conditions, including the actual through wall and party wall linings supplied by major UK manufacturers. Installation practices, interface treatments, and buildup sequencing were all selected to be representative of real construction rather than optimised for laboratory performance.
Performance that removes ambiguity
Both junction configurations achieved 90 minutes fire resistance, matching the published performance of the individual external wall and party wall constructions. Thermocouples installed directly at the junction demonstrated no adverse heat transfer, confirming that the interface did not create a localised weakness or undermine stability or integrity. In practical terms: the junction did not reduce system performance and the wall interface behaved as a continuous, compliant fire resisting element.
Why this matters for designers and contractors
Fire compartmentation depends on the consistent performance of every part of a wall assembly, not just the main through-wall build-up but also the junctions where different systems meet. By testing representative party wall/SFS junctions directly, this programme provides a clear and auditable understanding of how the interface performs as part of the overall compartment line.
- For designers, it provides confidence.
- For contractors, it provides clarity.
- For the wider industry, it helps close a gap that has been open for too long.
A step forward in transparency and confidence
This testing programme marks the first published evidence of its kind for party wall/SFS junctions. It supports a more transparent, evidence driven approach to fire performance and sets a benchmark for how manufacturers should demonstrate system behaviour in real world applications.