Movement challenges in passive fire protection
The Association for Specialist Fire Protection (ASFP) has reported on the need for greater focus on how building movement affects passive fire protection systems in the UK.
According to ASFP, structural movement can occur for several reasons, including dynamic loads, environmental pressures, material-specific behaviour, and thermal expansion during fire events.
It explained that these movements create risks for the long-term performance of firestopping systems, particularly where rigid materials are used around services or wall heads.
The body highlighted two types of movement: deflection, which is the displacement of structural elements such as slabs and partitions, and service movement, where cables, pipes, or ducts supported by soffits move and strain fire seals.
While products are available to address wall head deflection, ASFP noted that movement at service penetrations remains underrepresented in both testing and design standards.
Limitations in current UK guidance
ASFP reported that UK guidance such as Approved Document B does reference deflection movement but provides limited clarity.
The organisation explained that a nominal figure of 40mm is often used, but this is sometimes misunderstood.
It stated that the figure reflects an upper limit between unsupported elements and is not suitable as a blanket requirement across all building types or details.
ASFP added that misapplication of this value in design and installation can lead to incompatible or untestable solutions.
The association advised that further clarity is required in standards and practice to prevent overestimation or misinterpretation of movement allowances.
Testing service penetrations under movement
ASFP outlined that current fire test standards, such as BS EN 1366-3 for service penetrations, do not address service movement during fire exposure.
It explained that although BS EN 1366-4 Annex B includes a methodology for joint seal movement testing, there is little guidance on how services shifting within a sealed aperture behave in a fire.
To address this gap, Nullifire worked with Warringtonfire to create a hydraulic test rig that simulates wall movement before fire exposure.
ASFP said that the method, known as the “bouncy wall test”, aimed to replicate real-world conditions by applying stress before ignition.
The association noted that the test challenges the rigidity of current standards by reflecting the reality of long-term building use before any fire occurs.
Unrealistic movement requirements in design briefs
ASFP commented that design briefs sometimes request movement allowances of ±25mm to ±100mm, which it described as unrealistic.
It reported that movement of this scale would suggest structural deflection beyond acceptable performance.
The organisation explained that these figures can be carried forward unchallenged from early design through to procurement, resulting in unsuitable specifications.
It advised that accurate analysis of structural behaviour is needed to avoid arbitrary or excessive values being applied.
The group stated that heat maps and structural load analysis may be useful tools for setting more realistic allowances.
The role of education and engagement
ASFP emphasised the importance of early engagement between designers, specifiers, and contractors in understanding structural behaviour and passive fire protection performance.
It reported that greater awareness of material behaviour and mechanical support can help improve detailing at penetrations and deflection heads.
The association noted that training and technical dialogue are essential to prevent fire safety gaps arising from misunderstanding structural movement.
It stated that manufacturers and engineers should provide evidence-based clarity to support compliant solutions rather than rely on assumptions.
The body added that this work forms part of a wider industry effort to improve standards and testing for long-term building safety.
Relevance for fire and safety professionals
For fire and safety professionals, the ASFP’s report highlights the need to consider service and deflection movement as part of passive fire protection design.
The focus on movement testing methods shows how real-world performance may differ from laboratory results.
Understanding structural behaviour helps prevent failures in firestopping systems over time.
Professionals involved in design, specification, and installation may need to engage more closely with engineers and manufacturers to align expectations with realistic structural allowances.
Passive fire protection and structural movement in UK buildings: Summary
The Association for Specialist Fire Protection (ASFP) reported on movement in passive fire protection.
ASFP said structural movement occurs due to loads, environmental factors, material behaviour, and thermal expansion.
It stated that this movement threatens firestop system integrity at wall heads and service penetrations.
The group said Approved Document B provides vague guidance with a nominal 40mm allowance that is often misapplied.
It reported that BS EN 1366-3 does not address service movement and BS EN 1366-4 Annex B gives limited methodology.
Nullifire and Warringtonfire developed a “bouncy wall test” to simulate real conditions.
The group said some design briefs request unrealistic allowances of ±25mm to ±100mm.
ASFP advised using structural analysis and heat maps for realistic allowances.
It said education and early engagement are necessary to improve fire safety.
The association stated that manufacturers and engineers must provide compliant, evidence-based solutions.