Unlocking Building Safety: Identifying External Wall System Defects Through PAS 9980

In the wake of the Grenfell Tower tragedy, the importance of building safety has been thrust into the spotlight, particularly concerning external wall systems (EWS). The assessment and management of fire risk associated with external wall systems are now a primary focus for developers, building owners, and safety professionals alike. The publication of PAS 9980:2022, a standard that provides a consistent methodology for assessing the fire risk from external wall systems in existing buildings, marks a step forward in this domain.

The Context: Why External Wall Systems Matter

External wall systems are an integral part of any building’s envelope, comprising various components such as cladding, insulation, and cavity barriers. These systems are designed not only to provide thermal insulation and aesthetic appeal, but also to serve as a critical line of defence against fire spread. The tragic events of Grenfell Tower in London and Campanar in Valencia, revealed the catastrophic consequences that can arise when these systems fail to perform their intended function.

Post-Grenfell, the industry faced an urgent need to reassess the safety of existing building stock, particularly focusing on the fire performance of external wall systems. In response, PAS 9980 was developed to provide a clear framework for conducting fire risk appraisals of external wall construction in multi-occupancy residential buildings.

PAS 9980: An Overview

PAS 9980:2022 is a publicly available specification that offers guidance on conducting fire risk appraisals of external wall systems, specifically for multi-occupancy residential buildings. The document sets out a standard methodology for assessing the risk of fire spread over the external walls and provides a tool for prioritizing remedial actions based on the level of risk identified.

The PAS 9980 assessment process involves a detailed review of the building’s external wall system, considering factors such as materials used, the configuration of the wall components, and the quality of installation. It also takes into account the building’s overall fire safety strategy, including compartmentation, fire suppression systems, and means of escape.

Key Components of PAS 9980 Assessment

In the context of PAS 9980:2022, which provides guidance for conducting fire risk appraisals of external wall systems (EWS) in multi-occupancy residential buildings, assessments can be categorised into “Basic Level Assessments” and “In-Depth Level Assessments”. These levels reflect the depth and complexity of the assessment required based on the initial findings, the building's characteristics, and the perceived level of risk.

The initial approach towards Fire Risk Assessment of External Walls (FRAEW) is the basic assessment which is simplistic enough to serve as a quicker way of eliminating, as far as possible, the buildings that can be readily demonstrated that the risk of external spread of fire and its effect on life safety of occupants is within low or tolerable risk categories. Where it is not possible to conclude, from an FRAEW conducted using basic assessment whether the risk is tolerable or whether further refinements of the risk posed by external walls on existing buildings is deemed beneficial, an in-depth technical assessment is needed.

The following table outlines the key differences between the PAS 9980 basic assessment and the in-depth assessment:

Summary of Differences

In practice, many assessments will start as a basic assessment and based on the findings, escalate to an in-depth assessment if significant risks or uncertainties are identified. This tiered approach ensures that resources are focused where they are most needed, providing a balanced method of addressing fire safety concerns in external wall systems.

In the context of proportionality, related to both safety and remediation cost, the decision to transit from a basic level assessment to an in-depth technical assessment (to refine the risk) is very important.? The guidance note “Proportionality and risk when carrying out FRAEWs to PAS 9980”, produced by the Institute of Fire Engineers and the Fire Industry Association states that

“PAS 9980 High risk rating covers a wide range of risks, and so further clarification may be required to confirm the extent of the risk.” This suggests that a PAS 9980 basic assessment outcome delivering “high” risks should be further clarified, delivering the need to move into the realm and competence level of an in-depth evaluation, with Chartered Fire Engineers (CEng) being the recommended professional.

At Halliwell Fire Research we combine our local and global experience and fire hazard analysis expertise to deliver comprehensive services such as basic and in-depth fire risk assessment of the external walls. More on our Fire Risk Assessment of External Walls can be found here.

Thank you to Sahand Rasoulipour for his work on this article, watch this space for more insights from us!

DR SAHAND RASOULIPOUR, BSc, MSc, PhD (Fire Engineering) CEng MIFireE CPEng MEngNZ Senior Researcher | [email protected] | +44 (0)771 416 8058