How do you assess the risk of combustible materials in the external walls of buildings?

  • Market Insight 24 March 2022 24 March 2022
  • UK & Europe

  • Projects & Construction

This article briefly summarises the key contents of PAS 9980:2022, which is the new Code of Practice for fire risk assessments which need to be performed in connection with the external walls of buildings, which may contain combustible materials.

The Code provides a methodology for the appraisal of fire risks in such external wall systems. Whilst this is not its sole function, it is also directly applicable to the exercise that fire assessors will necessarily have to undertake to decide whether or not to provide an EWS1 certificate in respect of such walls, despite the two regimes having a different ultimate purpose:

  • the EWS1 certification process is primarily concerned with property valuation/mortgage lending; whereas
  • the Code aims to provide a consistent methodology for the assessment of fire risk in external walls, such that the appraisal is clear to all recipients, and can then inform the building’s overall fire risk assessment.

EWS1 assessments, and the assessors undertaking them are, potentially, more likely to err on the side of caution and accentuate the extent of the fire risks in their reports. This may be as a result of their instruction by the building owner (who may already be looking to the original contractor to rectify issues), but also because of their own risk/liability should a fire occur in a building rated incorrectly, or where further combustible materials are discovered.

By being more conservative and taking, in some cases, an absolutist approach to the removal of combustible materials, remedial works are necessarily going to be more extensive and expensive; the Code may help to redress the balance between risk and practicality and cost.

Combustible materials – a more common-sense approach?

Whilst there are a number of factors which the Code requires assessors to take into account, one which necessarily will carry a higher weighting (note that there is no specific guidance within the Code to quantify the weight which each of the individual factors is to carry) is the presence (or possibility of the presence) of combustible materials.

There is nothing in the Code to prohibit the use of combustible materials in external wall systems, or to suggest that the mere presence of these materials presents a problem in itself. In fact, the Code expressly recognises that they are likely to have been used:

It is inevitable that some combustible components are present in the buildup of any external wall. Typically, these include components such as: seals and gaskets, sealants, fixings, breather membranes, vapour control layers, including membranes around windows, and backer rods

Whilst the presence of combustible materials can be an indication of fire risk, this should be part of a wider holistic assessment that also considers the quantity and location of those materials, amongst other factors.

The approach of the Code is to support its stated aim of emphasising ‘the importance of proportionality in relation to risk and associated mitigation measures, including considerations of benefit gained, practicality and cost’. It is only by accounting for all circumstances that measured recommendations can be provided, in keeping with the goal of acting proportionately and not creating any undue financial burdens. 

Michael Gove, the Secretary of State for Levelling Up, Housing and Communities, has confirmed that he wants to see more ‘common sense’ applied in the approach to identifying and remediating fire risks in buildings. The Code is clearly directed to achieving this.

This is should all  be welcomed as it represents a pragmatic move away from what is considered by many in the industry to have been an overly rigid or inflexible approach (from the Government) to building safety risks, particularly in relation to fire.

A complete solution?

Whilst the Code provides a clear process to be followed, this does not mean that a simple outcome is going to be arrived at, whether there is a joint assessor, or if each (or every) party has their own.

The Code places emphasis on the subjective appraisal of the assessor and it is envisaged, in the industry commentary, that this could lead to inconsistent findings and outputs. Based on our experience we are inclined to agree.


The clear intent of the Code is to promote a holistic approach to identifying and quantifying fire risk. The advantage here is that parties are unable to use the mere presence of combustible materials simply to say an unacceptable fire risk exists, mitigating the more absolutist approach of some EWS1 assessors.

However, the presence and level of combustible materials is one of the most important factors in determining the fire risk, with Clause 13 confirming that the presence of combustible materials can result in an assumption that the risk is high, and must be alleviated by other factors, e.g. location and quantity of such materials.

Whilst the distinction for inconsequential levels of combustible materials is helpful, no definition of ‘inconsequential’ is provided. This will therefore depend on the specifics of the building and the judgement of the assessor.

It is entirely conceivable that there will be disagreement between assessors as to what amounts to an inconsequential amount of combustible material. This point has been picked up in the industry’s criticisms of the Code, and there is concern that this inherent subjectivity will create uncertain and inconsistent outcomes.

Some practical tips

The assumption which must be taken on the existence of combustible materials is that, unless the extent of the material is so low that a fire risk appraisal of external wall construction (“FRAEW”) need not be undertaken in the first place, the fire risk must necessarily be towards the higher end.

It is then only during the appraisal process that the risk may be reduced (depending on the materials used, their location, and their extent). The assessor will need to understand all of these points. To best assist the assessor and provide all parties involved with the clearest direction possible (which can only be of benefit), we would advise collating the following in readiness for an assessment:

  • Details of the external walls’ construction – both planned and actual, the latter preferably supported by photographic evidence;
  • Material information (such as data sheets) and manufacturer’s installation instructions; and
  • Any data as to the surveys which have already been undertaken.

Under the Code the assessor has a wide discretion on how they are to satisfy themselves on the risk posed by the construction of the external wall. The level of the information available will dictate the extent of the site surveys which they wish to be carried out, what sampling they consider should be performed and if any opening up work is required.

Where there are multiple wall systems, occupied buildings or access issues, any limiting of the opening up that is required is going to be of benefit, in terms of both the time and the cost involved, not just in relation to the risk appraisal but also in respect of the remedial steps which might follow.



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