Summary
New research has highlighted how the performance of fixings securing mechanical and electrical (M&E) services to timber ceilings can change during fire conditions. Through a programme of fire testing, the study found that heat conducted through steel fixings can weaken the surrounding timber and reduce load-bearing capacity long before significant charring occurs. One of the most significant findings was that larger-diameter fixings can lose strength more rapidly in fire than smaller alternatives due to their ability to conduct heat deeper into the timber. The research also identified practical and readily available solutions, showing that longer, slimmer hardened-steel fixings can provide substantially improved performance. The findings will help inform future standards, guidance and industry best practice, supporting the continued safe and resilient growth of mass timber construction.
About the study
As mass timber construction becomes increasingly important in delivering net-zero objectives, it is essential that fire safety guidance, standards and engineering solutions continue to evolve alongside its growing use. New research led by Professor James Glockling contributes to this process by investigating the fire performance of fixings used to secure mechanical and electrical (M&E) services to timber ceilings and identifying practical solutions that can enhance safety for occupants and firefighters.
The study, Preventing Firefighter and Evacuee Entanglement, Electrocution and Obstruction Risks in Timber Buildings on Fire, was authored by Professor James Glockling with support from ASBP.
Commissioned by the Fire Service Research & Training Trust (FSRTT), the project investigates how the fire performance of fixing systems can be optimised for timber structures, helping to inform future standards, guidance and industry best practice.
Supporting the next generation of construction
Mass timber has an important role to play in reducing the embodied carbon of buildings and supporting the transition to a low-carbon built environment. As with any evolving construction system, increasing adoption creates opportunities to further develop technical guidance and ensure that standards continue to reflect the latest knowledge and experience.
One area identified for further investigation is the attachment of ceiling-mounted M&E services, including ventilation systems, pipework, electrical services and fire suppression systems.
Detailed standards and guidance already exist for fixing systems in traditional concrete structures. As mass timber construction becomes more widely adopted, there is an opportunity to develop the same level of detailed guidance for timber structures, ensuring that performance during fire conditions is fully understood and appropriately addressed.
The study focuses on how fixings behave during fire and whether heavy M&E services remain securely attached for the critical period required to support safe evacuation and firefighting operations.
Enhancing fire resilience in mass timber buildings
Should ceiling-mounted services become detached during a fire, they could create hazards for occupants and emergency responders, including entanglement, electrocution and obstruction risks.
In addition to the immediate safety implications, detached services could potentially affect the operation of other building systems, including:
- Fire detection and alarm systems.
- Emergency lighting.
- Smoke control systems.
- Fire suppression systems.
- Ventilation systems and compartmentation measures.
Understanding and addressing these scenarios is an important part of ensuring that fire safety design continues to evolve alongside changing construction methods.
Applying lessons from past incidents
A key driver for the study was the tragic fire at Shirley Towers in Southampton in 2010, where firefighters Alan Bannon and James Shears lost their lives while responding to a fire in a high-rise residential building.
The subsequent investigation highlighted the dangers posed by fallen electrical cables, which created entanglement hazards and obstructed escape routes. The incident ultimately led to significant changes in wiring regulations, including requirements for fire-resistant cable supports.
The report draws a parallel between the lessons learned from Shirley Towers and the importance of understanding how M&E fixing systems perform in timber buildings during fire conditions.
While the underlying mechanisms are different, the study highlights the value of identifying potential risks early and developing practical solutions before they become operational challenges.
Advancing knowledge of fixing performance in timber buildings
The research builds on earlier work undertaken by Dale Kinnersley of the Fire Protection Association and RISCAuthority, which examined the fire performance of sprinkler pipework fixings in timber structures.
Using a purpose-built test rig, the project investigated how a range of factors influence fixing performance under realistic fire conditions, including:
- Embedment depth.
- Diameter.
- Material type.
- Thread pitch.
- Applied load.
- Fire exposure.
- Contact surface area.
The findings revealed that fixing performance under fire conditions is influenced not only by visible timber charring but also by the transfer of heat through the fixing itself into the surrounding timber.
One of the most notable findings was that larger-diameter fixings, while capable of carrying greater loads under normal conditions, can lose performance more rapidly under fire exposure than some smaller alternatives.
Understanding the science
To explain this behaviour, the report introduces two conceptual models: the “fat” fixing model and the “skinny” fixing model.
In the “fat” fixing model, larger-diameter fixings conduct heat more effectively into the timber, raising temperatures around the embedded threads and reducing the strength of the surrounding material.
In contrast, the “skinny” fixing model demonstrates how longer, slimmer fixings can reduce heat transfer and maintain thread engagement within cooler, unaffected timber for longer periods.
The research shows that, under fire conditions, fixing geometry can be just as important as load-bearing capacity when considering overall performance.
Practical solutions for improved performance
One of the most encouraging findings from the study is that effective solutions are already available and can largely be achieved using existing products and installation methods.
The research concludes that fixing performance can be enhanced through:
- Understanding the critical period during which M&E services must remain in place.
- Understanding the rate at which heat penetrates the timber substrate.
- Selecting fixings with sufficient embedment depth to maintain engagement within unaffected timber.
- Minimising heat conduction into the timber through appropriate fixing selection.
- Using hardened steel fixings capable of maintaining integrity during fire exposure.
In practical terms, the study identifies long, slender, hardened-steel fixings as a particularly promising solution, offering improved performance while remaining compatible with current construction practices.
Importantly, the report concludes that these improvements can generally be achieved without significant additional complexity or cost.
About the Author
Professor James Glockling is a Principal Fire Protection Engineer within the Naval Engineering Team at BMT, consultant, and Chair of BSI FSH/16 Hazards to Life from Fire. He holds a degree in Chemical Engineering and a PhD in Nuclear Engineering.
Following postdoctoral research, he worked as a lecturer in Chemical Engineering and Fire Safety Engineering, a forensic fire investigator, and a research leader at the Loss Prevention Council (LPC), Building Research Establishment (BRE) and the Fire Protection Association (FPA), where he managed the UK insurance industry’s research programme, RISCAuthority.
His principal areas of expertise include fire detection and suppression technologies and the mitigation of complex fire risks. He is also a Visiting Professor at the University of Central Lancashire and continues to work with the commercial built environment and maritime sectors to improve resilience.
Acknowledgements
The project was funded by The Fire Service Research & Training Trust and supported by The RISCAuthority, with materials kindly donated from KLH and Midfix.