Why is PAS 9980 being misinterpreted?

Since its publication last year, PAS 9980 has been frequently misunderstood – so in the first of two articles, the code's co-authors explain how it should be properly applied


  • Dr David Crowder
  • Neal Butterworth
  • Mostyn Bullock
  • Colin Todd
  • Steven Daws
  • Bart Kavanagh

10 October 2023

Fire extinguisher and fire exit door

PAS 9980: 2022 Fire risk appraisal of external wall construction and cladding of existing blocks of flats. Code of practice, which was published in January last year, was developed for three key reasons.

First, it was designed to keep people safe from fires associated with external wall construction. Second, it aimed to prevent financial hardship for occupants wherever possible. Third, it sought to promote a competent and consistent approach to fire safety.

Grenfell Tower tragedy prompts urgent reforms

The need for such a code of practice arose from revisions to regulations and guidance since the Grenfell Tower fire of 2017. In the immediate aftermath of the fire, it became clear that problems in external wall construction went much further.

Among the government's many initiatives, it set up an expert panel that issued guidance on how to safeguard residents, particularly those living in blocks found to have the same aluminium composite material (ACM) cladding. Immediate action was needed to avoid the risk of a repeat tragedy.

The guidance came in the form of advice notes. The first group of these dealt with the clear and present danger posed by unmodified polyethylene ACM, as had been used on Grenfell Tower; the second group considered the implications of large-scale testing on various grades of ACM; then more widely, a third group looked at other relevant forms of external wall construction. A total of 22 advice notes were published and variously updated.

A Consolidated Advice Note (CAN) was ultimately published in January 2020 to replace the preceding 22, with the aim of moving the construction industry in the right direction.

Even that was only the beginning of what needed to be done, though, and the CAN was ultimately withdrawn two years later to coincide with the publication of PAS 9980.

Related article

What you need to know about PAS 9980

Read more

New guidance aims to provide key knowledge

Those working on the external wall construction of existing buildings came to realise that there was no textbook available to fire engineers or other construction professionals about how an external wall might be expected to behave when exposed to fire.

Publications such as BR 135 Fire performance of external thermal insulation for walls of multistorey buildings advised what features would be good to design into various forms of external construction.

But it is only through large-scale testing carried out against standards such as BS 8414 Cladding testing that one expects to find out whether a particular design works; and there is no central repository of all the experience gained from such testing.

In fact, there was only a very small pool of professionals whose experience covered the fire behaviour of external walls, fire engineering design and fire risk assessment.

This lack of industry-wide knowledge about the fire behaviour of external walls meant the advice notes had numerous unintended consequences.

Although the notes referred to the need to consider risk where buildings did not comply with Approved Document B, assessors were taking a purely compliance-based approach to assessing external walls – condemning buildings on the basis that any combustible material was present, without considering the manner in which it had been incorporated into the construction.

As a result, residents were being exposed not to fire risk but extreme and unnecessary financial burdens and stress.

In certain circumstances significant costs will sadly be unavoidable to ensure buildings' external wall constructions are safe.

But incurring such cost needs to be a conscious decision based on sound engineering and scientific judgement, rather than a lack of understanding that prompts risk-averse behaviour, or a desire to render a building more compliant than necessary with current standards at someone else's expense.

BSI seeks to provide authoritative advice

Development of PAS 9980 therefore began in September 2020, and it was published in January 2022. It provides technical guidance on how the various types of products and systems incorporated into external wall construction can be expected to behave, and a methodology to conduct and record fire risk appraisals of external walls (FRAEWs).

It therefore necessarily contains a lot of information, but can be scaled up or down depending on a building's complexity.

Industry-wide consultation was carried out to ensure consensus on the guidance, and at the time it received the most comments for any standard in the history of BSI.

This feedback was considered by the code's authoring team and steering group, of which RICS was a member, and the volume of responses gave particular authority to the resulting document.

It is worth noting that PAS 9980, being a publicly available specification from the British Standards Institution (BSI), was prepared for the three key reasons detailed above, and to a timescale shorter than is normally the case for a full British Standard.

Being a first edition, the document therefore represents an initial attempt to set out state-of-the-art knowledge about the fire performance of external walls.

Furthermore, PAS 9980 is merely guidance; users are not obliged to write reports that comply fully with its recommendations. 

However, where an FRAEW report does claim to be fully compliant then the relevant recommendations from the standard must be properly followed, or it runs the risk of being misleading.

Issues still arise from misunderstanding PAS

PAS 9980 has now been in circulation and use for nearly two years. As the code authoring team we have, to various degrees, been producing our own FRAEWs in line with the guidance, reviewing those produced by others, and seeing what the construction industry makes of the code.

We have seen a range of approaches to its application, and noted that either:

  • FRAEW authors have diverged from PAS 9980 guidance where they claim to comply with it
  • the intent behind the code has not been properly implemented by FRAEW authors because they misunderstand the guidance.

Some of the issues that we have become aware of are presented below; but all of them result from a failure to acknowledge, accept and account for the fundamental principles of PAS 9980.

  • Compliance versus risk: the code is principally meant for assessing existing buildings where there is uncertainty about the adequacy of the external wall construction; by contrast, there should be more confidence that new buildings have suitably constructed external walls. PAS 9980 accepts that as-built construction might not comply with Approved Document B, or similar requirements, whether due to the design or to the quality of the work. Instead, the code methodology is risk-based, requiring identification of potential fire hazards and an assessment of the probable consequences for occupants.
  • Risk tolerance: Zero risk and perfect construction are not possible, necessary or appropriate. In fact, PAS 9980 accepts that while the risk might be heightened – above the level required to comply with Approved Document B or similar, or even the broader Building Regulations it might still be low enough to be tolerable, especially if the measures necessary to reduce that risk are disproportionate to it.
  • PAS conformity: PAS 9980 defines a methodology for FRAEWs, but this is a loose definition and not only allows but requires competent interpretation and application. In turn, this means that FRAEWs for the same building might differ significantly. However, to accord with the code an FRAEW must as a minimum be risk-based, considering fire performance, facade configuration and fire strategy factors relating to the wider fire safety arrangements in the building and the way these interact with the external wall.
  • Information certainty: The standard is intended for application to existing buildings, and aims to gauge actual risk at the time of such assessment. As such, there needs to be sufficient information about the physical building to enable adequate assessment, while the assessor must be as certain about that information as is commensurate with the extent they rely on it in their assessment. For example, the building inspection is likely to require intrusive investigations in certain areas, which are costly and damage the facade. Therefore, inspection of the whole facade is not feasible, and the assessor has to make a judgement about the location and number of any such investigations.
  • Fire performance, facade configuration and fire strategy factors: Compliance with PAS 9980 not only requires consideration of fire performance of an external wall construction, but also necessitates assessment of how this would affect the fire strategy, given the way the wall construction is configured. This means that the risk might be tolerable, even if the fire performance is poor.
  • Risk rating method: PAS 9980 provides guidance on whether aspects of the external wall construction are likely to have a positive, negative or neutral effect on the overall risk. However, it also requires that the actual impact of each aspect must be considered in the specific context of a wall construction and building. In other words, it is feasible for an aspect to be negative in one instance but positive in another, so one particular negative might have a greater impact than another; or, one particular negative might significantly outweigh a positive or vice versa. For example, a rendered polystyrene external wall system might be classified to BR 135 as a result of successful testing against BS 8414. While the polystyrene would be assigned a negative rating as an insulation material, the system overall would be deemed positive as a result of the BR 135 classification, a scenario in which the positive factor significantly outweighs the negative.
  • Building type: Although PAS 9980 was written specifically for blocks of flats, the methodology can be applied to all buildings. That said, one of the implicit assumptions is that a stay-put policy is in place, as remains the norm for most purpose-built blocks of flats. As such, careful consideration must be given to whether specific aspects of the building's fire strategy have a positive, neutral or negative effect on the overall risk, and their relative weighting. For example, the PAS 9980 guidance might not be appropriate when applying the method to buildings other than blocks of flats.

While some examples of our experiences are summarised below, a second article will deal with more specific issues that occur in completing FRAEWs.

'The PAS 9980 methodology is risk-based, requiring identification of potential fire hazards and an assessment of probable consequences'

Compliance assessments do not amount to FRAEWs

In monitoring the application of PAS 9980, we have seen reports that are presented as FRAEWs but are in fact simply an assessment of whether a building complies with Approved Document B or, more broadly, the Building Regulations.

While we expect users of PAS 9980 to consider and understand the regulatory context in which a building was constructed – and potentially the current regulation as well, particularly in relation to remedial works – this should not be the sole basis for an assessment of the actual life safety risk that the as-built construction presents in the event of fire.

Guidance such as Approved Document B, BS 9991 Fire safety in the design, management and use of residential buildings – Code of practice, and the since withdrawn CAN, may be used to inform assessment of fire performance, facade configuration and fire strategy factors; however, these should not be a benchmark of acceptable risk.

Doing so could mean that confirmation bias influences the assessment and proposed remediation towards a presumption of compliance.

We have seen many assessments that use Approved Document B compliance or the CAN as the benchmark of risk. As a result, they conclude that any failure to comply with the approved document automatically constitutes a risk that is not low enough to be tolerable, and the only viable way to reduce it is to reinstate the construction so that it would have complied.

In some instances, this approach of focusing only on compliance appears deliberate, while in others it is probably due to subconscious confirmation bias.

In others still, it might be due to inadequate competence to assess risk, or a reluctance to take responsibility for remediation measures that are not demonstrably compliant with the current Approved Document B.

In extreme cases, reports are presented as FRAEWs but are actually assessments in accordance with the CAN; or they only deal with fire performance factors, which describe the likelihood of fire spread across a surface.

Sometimes they even just address the combustibility of materials without considering cavity barriers or other encapsulation. These reports fail to consider the actual hazard associated with the fire performance, completely ignoring the facade configuration and fire strategy factors.

Similarly, there are reports that have assessed the as-built construction for compliance with BS 9414 on the fire performance of external cladding systems, despite PAS 9980 guidance being at pains to advise that such use is not appropriate.

'In extreme cases, reports fail to consider the actual hazard associated with the fire performance'

Risk tolerance and response require rigour

Tolerance of risk is inherently subjective; each professional will have their own view as to what level is tolerable. However, some approaches clearly fall outside the range contemplated by PAS 9980.

For instance, some reports conclude that minor defects necessarily constitute a heightened risk that needs reducing, but do not properly consider the actual risk or the proportionality of the proposed remediation.

What constitute minor defects are of course building- and system-specific; but they might include poor-quality cavity barrier installation where there is only limited reliance on these, or small differences in cavity width or insulation thickness from those required by BR 135.

Other reports go on to define the remediation or interim measures required but without proper stakeholder input.

Assessments in accordance with PAS 9980 can be used to determine whether permanent or interim risk reduction is required, to identify possible options, and assess how likely they are to be effective.

However, PAS 9980 appraisals in isolation cannot define the most appropriate option. This is because the risk reduction must be proportionate – which requires stakeholder input to assess – and also needs a proper design and specification process.

Similarly, whether interim measures are appropriate and would be effective can only be determined as part of the fire risk assessment.

We have seen many reports defining the remediation required where there has obviously been no identification of clearly available alternatives, no stakeholder engagement, and no consideration of whether it is in fact achievable or sustainable.

This can lead to unnecessary cost and disruption and ineffectual risk reduction, while the appraiser may also assume unintended liability by inadvertently acting as a fire risk assessor, designer or responsible person.

Likewise, we have also seen reports that recommend a waking watch patrol and simultaneous evacuation strategy without properly assessing whether such measures are appropriate, implementable or effective.

PAS focuses on risk, performance and competence

Where a report presents itself as being an FRAEW that is in full accordance with PAS 9980 then it needs to follow the entire process set out in the guidance. A report only addressing part of the standard is not prohibited; but where this is the case it needs to be made clear to the reader.

As has been said, to conform with the standard the assessment must be risk-based and must consider fire performance, facade configuration and fire strategy factors.

We have seen many assessments that conflate combustibility, hazard and risk, assuming that because a material is combustible it can be ignited, will burn and, in burning, constitutes both a hazard and a risk.

This is not always the case. For instance, combustible materials will not be ignited if they are encapsulated, while adequately subdivided materials will not result in undue fire spread.

Even if fire does spread it would not constitute a hazard where for example the construction is limited in area, and hazards can themselves present a low risk of harm.

For example, feature areas of combustible cladding might only occur at the boundaries of individual flats and otherwise be surrounded by construction that does not allow fire spread.

In such a scenario an individual area might catch fire and burn, but this would not lead to that fire spreading across multiple flats or compartments.

Reports must follow correct format

Section 15 of PAS 9980 sets out how FRAEWs should be reported – yet we have seen many instances where assessments fail to conform with the code because they do not follow the required format.

For instance, one aspect that is often not included in reports purporting to conform with PAS 9980 is a statement of competence.

The code makes clear that the preparation of a suitable and sufficient FRAEW requires adequate competence on the part of the appraiser, and that evidence of said competence be provided in the report. This can be in the form of a statement of competence, or by appending a professional CV.

There is no one uniform answer to the question of what competence a person needs to complete an FRAEW, which will depend on the issues presented by a particular building. So it is entirely possible for an individual to be competent to work on one FRAEW but not another.

Clause 8 and Annex H of PAS 9980 provide extensive guidance on what is expected in terms of competence, depending on the complexity of the appraisal being completed. Compliance with the former also requires the FRAEW report to record the competence of its authors.

As with all fire safety activity, it is also important that FRAEWs are completed in an ethical manner.

This means, for example, that wherever chartered engineers are reviewing and signing them off, they should do so carefully to ensure, as far as possible, that the findings presented are consistent with those they would have reached had they conducted the appraisal themselves.

Other professionals doing so need to be able to demonstrate competence equivalent to that of a chartered engineer.

While this article has covered some of the general trends we have witnessed in the application of PAS 9980, the next will deal with more specific issues arising in FRAEWs produced to date – and how these might be avoided in future.

'Preparation of a suitable and sufficient FRAEW requires adequate competence on the part of the appraiser'

This article has been prepared in consultation with the National Fire Chiefs Council (NFCC). We gratefully acknowledge NFCC input in collating and summarising issues that its members have faced when reviewing FRAEWs that purport to comply with PAS 9980 as part of their work to enforce the Regulatory Reform (Fire Safety) Order 2005.


Dr David Crowder is a partner at DCCH Experts
Contact David: Email


Neal Butterworth is a director at Design Fire Consultants
Contact Neal: Email


Mostyn Bullock is a director at Tenos
Contact Mostyn: Email


Colin Todd is managing director at C.S. Todd & Associates
Contact Colin: Email


Steven Daws is a senior consultant and quality manager at C.S. Todd & Associates
Contact Steven: Email


Bart Kavanagh is a partner at Expert Architect Studio
Contact Bart: Email

Related competencies include: Ethics, Rules of Conduct and professionalism, Fire safety, Inspection

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