Posts tagged: Engineering

Ahmed Allam, Director of Fire Engineering at WSP, examines the Grenfell Tower Inquiry Phase 2 recommendations and the urgent need for regulatory reform and professional accountability

The Grenfell Tower inquiry revealed serious weaknesses in fire safety, especially regarding the material type and compliance with building regulations.

Lessons for fire engineers, developers and contractors as well as building operators have been identified from the Phase 2 Inquiry and emphasise the need for better engineering knowledge of a range of issues including fire engineering practices to treatment of materials and systems.

As a professional, I appreciate the significance of the final Inquiry report and its comprehensive recommendations, The tragedy of June 14, 2017, together with the discovery of systematic building defects across multiple buildings in the UK and internationally, represents a watershed moment for our industry.

The work of the Inquiry has revealed systemic problems with the way the built environment is developed, and we must take stakeholders on this transformation journey together to put in place an approach to reform that will transform accountability throughout the sector.

Material fire classifications

The Grenfell disaster highlighted the risks of selecting combustible materials like Aluminium Composite Material (ACM) cladding with polyethylene cores.

This material failed to meet both British Standards (BS 476) and European Standards (EN 13501-1), raising critical concerns about material classification.

British Standards (BS 476): Focuses on fire resistance, flame spread, and combustibility, categorising materials by classes and ratings, with “non-combustible” determined through BS 476-4 tests.

European Standards (EN 13501-1): Provides a broader classification, rating materials on reaction to fire (A1-F), smoke production (s1-s3), and burning droplets (d0-d2).

A1 materials are entirely non-combustible, while A2 are of limited combustibility.

The prioritisation of non-combustible materials (A1 or A2) is essential, particularly in high-rise residential buildings, to minimise risks associated with material choice.

This requirement applies to buildings that meet the definition of “relevant buildings,” which includes high-rise residential buildings over 18 meters in height, hospitals, care homes, and student accommodation.

The guidance is detailed in Approved Document B (ADB), 2019 edition, Volume 1, under Section 10 Weaknesses in UK Building Regulations highlighted significant shortcomings in the UK’s Approved Document B (ADB), particularly relating to the National Classification system, including Class 0, which allowed for ambiguities regarding the fire performance of external wall systems.

One of the issues was that materials meeting Class 0 standards (under the now-withdrawn BS 476-6 and BS 476-7) could still be combustible, as the classification focused on surface spread of flame rather than overall combustibility.

In response, subsequent updates to ADB have removed references to Class 0 and aligned requirements with European standards.

The most recent version of Approved Document B (2022 edition, incorporating 2023 amendments) now exclusively references Euroclass standards (BS EN 13501-1) for the classification of materials’ fire performance.

Early involvement of fire engineers during the design stages is crucial to ensure compliance and integrate robust fire safety strategies.

Escape routes and compartmentation

Grenfell demonstrated the catastrophic consequences of poor compartmentation and inadequate evacuation planning.

Combustible materials compromised fire barriers, while shared stairwells increased confusion during evacuation.

Going forward, fire engineers must prioritise fire compartmentation and the separation of emergency escape routes.

Adherence to fire-rated construction standards and rigorous testing of fire containment and evacuation strategies is vital for high-rise buildings.

Lessons for developers and contractors

Grenfell underscores the necessity for developers and contractors to prioritise fire safety.

Thorough vetting of materials and systems, adherence to fire standards and engagement with experienced fire consultants is imperative.

Fire safety cannot be compromised for cost-saving or expediency.

Every project detail must align with regulations to safeguard lives.

The UK is progressively moving away from the BS 476 series of fire tests in favour of the EN 13501-1 classification system, which aligns with European standards for fire testing and classification.

This transition is evident in government and industry guidance.

Engineering judgement

An engineering judgment is an evaluation of the anticipated performance of a proposed fire safety measure, such as fire stopping, that has not been specifically tested.

These judgments rely on the performance of tested systems and established engineering principles, applying broadly to various fire mitigation measures.

Sound engineering judgment is based on decisions that align with established scientific and engineering knowledge, as well as relevant information supported by technical studies employing appropriate methodologies.

In fire protection design, engineering judgment is used to assess the likely performance of fire-stopping systems that have not undergone fire testing.

These evaluations are grounded in scientific principles and the proven performance of verified designs.

Where possible, reliance should be placed on tested systems rather than engineering judgment.

Judgments must originate from qualified technical experts, ensuring that the assessments are reliable and credible.

Engineering judgments should draw on the most relevant tested and verified systems to establish a sound basis for decision-making.

In the absence of applicable test data, judgments cannot replace testing, as experimental evidence remains critical to verifying performance.

Engineering judgments apply only to the specific conditions under which they were made.

Each evaluation is unique to a particular project and cannot be applied to another without careful reconsideration.

These appraisals must also address and substantiate any discrepancies between the tested design and the actual construction.

Performance-based fire engineering: insights from BS 7974

The Grenfell Tower Inquiry Phase 2 report highlights critical insights into performance-based fire engineering design, particularly the catastrophic role of combustible materials such as Aluminium Composite Material (ACM) cladding in accelerating flame spread.

It calls for stricter enforcement of material fire classifications, prioritising non-combustibility and rigorous compliance with updated regulations.

The report also recommends extended performance evaluations for high-risk materials to balance innovation with safety, underscoring the importance of caution when lives are at stake.

Performance-based approaches, while offering flexibility, must prioritise safety.

Grenfell demonstrated that adherence to both prescriptive and performance-based standards could have mitigated the disaster.

This the need for exhaustive testing of performance-based designs, especially when employing innovative or non-standard materials, a crucial consideration for fire engineers, developers, and contractors managing high-risk projects.

BS 7974 provides a framework for applying performance-based fire safety principles, enabling tailored solutions for specific building designs and fire risks.

This approach complements prescriptive codes, allowing for a more nuanced and adaptable fire safety strategy.

Concerning Grenfell, the inquiry emphasised the failure of the prescriptive approach (as seen in the inappropriate use of combustible materials in cladding) and the need for a more holistic, risk-based approach to fire safety in complex buildings.

This would align with BS 7974, which encourages engineers to:

1. Assess fire risks specific to the building, considering factors such as occupant behaviour, building use, and design.
2. Develop tailored fire safety strategies, which might include active systems (sprinklers, alarms) and passive systems (compartmentation, fire-resistant materials).

Key fire engineering lessons related to BS 7974:

Material performance: The fire spread at Grenfell demonstrated that prescriptive rules alone (e.g., building height restrictions on the use of certain materials) were inadequate.

Performance-based methods could allow fire engineers to evaluate materials more rigorously under realistic fire conditions.

Fire modelling and risk assessment: BS 7974 advocates for the application of advanced fire modelling tools and quantitative risk assessments to predict fire spread and evacuation dynamics, offering the potential to significantly enhance design decision-making, as exemplified in the case of Grenfell Tower.

These sophisticated methodologies are typically reserved for complex, high-risk developments where tailored fire strategies are deemed essential.

However, over-cladding projects, often perceived as straightforward refurbishments, generally adhere to prescriptive guidance such as Approved Document B, without the need for in-depth fire engineering assessments.

This underscores an important oversight: the tendency to underestimate the potential fire risks associated with less complex projects, which nonetheless merit rigorous evaluation and scrutiny.

Escape Strategies: A performance-based approach would enable a detailed evaluation of evacuation strategies, accounting for building layouts and the interaction between fire services and occupants.

By modelling scenarios where “stay put” fails, could encourage the integration of measures such as evacuation lifts, automatic alarms, and smoke management systems.

While the Grenfell Tower Inquiry Phase 2 report does not specifically promote BS 7974 or performance-based design, its findings point to the need for more comprehensive, flexible fire safety strategies that can adapt to the complexities of modern construction, where BS 7974 could play a pivotal role.

Integration across RIBA stages

The Grenfell Inquiry highlighted poor coordination between fire engineering and other disciplines across the RIBA Plan of Work stages.

Enhanced collaboration is critical to avoid systemic failures.

Here are some stage-specific actions:

Stage 1 (preparation): Establish fire safety objectives early, integrating input from fire engineers.

Stage 2 (concept design): Develop fire strategies alongside initial designs to ensure feasibility and safety.

Stage 3 (spatial coordination): Align fire protection systems with structural, mechanical, and electrical designs.

Stage 4 (technical design): Ensure technical specifications are consistent with fire safety requirements.

Stage 5 (construction): Implement robust quality control to prevent non-compliance.

Stages 6 & 7 (handover & use): Ensure operators understand fire strategies and establish processes for ongoing risk assessment and maintenance.

Accountability and competency

The Inquiry highlighted a lack of accountability and professional standards across the construction industry.

Deregulation, cost-cutting, and fragmented oversight contributed to the failures at Grenfell.

To address this, we should: implement stringent competency checks, including certifications and continuous professional development for fire safety professionals; Foster a culture of accountability where all stakeholders are responsible for fire safety outcomes; and strengthen enforcement mechanisms to ensure compliance with fire safety regulations.

Reflections on Dr.

Barbara Lane’s recommendations

Dr. Lane’s report for the Phase 2 Inquiry provides critical recommendations but leaves room for refinement.

While her report for the Phase 2 Inquiry offers crucial insights, some aspects could benefit from greater detail and clarity.

Broader testing frameworks are needed to assess how multiple materials interact under fire conditions.

This would enhance the understanding of composite behavior during fires and inform safer design practices.

The report lacks a detailed implementation framework, particularly in terms of how the recommendations should be enforced and integrated into existing fire safety standards.

Clear guidance in this area would aid regulators and practitioners in applying the recommendations effectively.

Another key area for refinement is the definition of competency metrics.

Establishing clear qualifications and training standards for fire safety professionals is essential to ensure consistent and reliable expertise across the sector.

The report could also place greater emphasis on retrofitting existing buildings to meet modern fire safety standards.

Addressing legacy risks is a critical component of improving overall safety.

Finally, evacuation plans must account for diverse occupant needs, including those with mobility challenges.

Occupant-centric strategies are vital for ensuring that fire safety measures protect all building users effectively.

Summary and final thoughts

The Grenfell Tower Inquiry Phase 2 report calls on fire consultants, developers, contractors, and building operators to prioritise compliance with material fire classifications, enhance adherence to UK building regulations, and engage fire engineers early in the design process.

These measures are vital to preventing future tragedies and safeguarding residents while upholding the highest fire safety standards.

The report emphasises the need for a holistic, system-wide approach to fire strategies, with clear accountability among all stakeholders.

A key issue identified was the fragmentation of responsibilities, particularly in fire strategy development and building design.

To address this, fire strategies must be treated as dynamic, living documents, integrating fire engineering, material performance, and building operations.

Regular updates are essential to reflect changes in building use, design, or risk assessments under the Regulatory Reform (Fire Safety) Order 2005 (RRO).

Robust fire strategies require rigorous testing and certification of materials, systems, and escape routes, supported by seamless collaboration between fire engineers, operators, and regulators.

The report also highlights the importance of lifecycle resilience, advocating for stringent testing protocols and transparent product certification.

Continuous revalidation of fire strategies ensures evolving safety standards are met, fostering a culture of accountability and long-term industry commitment to fire safety reform.

This article was originally published in the February 2025 issue of International Fire & Safety Journal – to read your FREE digital copy, click here.