Cladding Remediation Programme: Single Building Assessment specification

3 Assessing External Wall Construction

3.1 Overview

3.1.1 In January 2022, BSI published PAS 9980 to replace the UK Government’s CAN on life safety. The PAS 9980 document was released to take a more risk-based and proportionate approach to life safety. An independent group of experts, led by Dame Judith Hackitt, concluded that there had been a disproportionate reaction to the ‘medium’ risk level and risk in lower-rise buildings, while using the CAN. This included assessors taking a risk averse approach in identifying risks within EWS and recommending remedial actions which could be perceived as unnecessary. Therefore, the PAS 9980 was issued to provide a more standard methodology and a more consistent assessment of the risk of fire spread across different EWS types.

3.1.2 In the UK the PAS 9980 guidance document is the current industry standard code of practice for undertaking FRAEWs and is used widely across England and Wales. The level of detail contained within the document should lead to a better standard of reporting from the Assessors, provided that the methodology is followed. PAS 9980 is to be used in Scotland for the purpose of undertaking the FRAEW section of an SBA. The document should be followed in full when undertaking an FRAEW and the reporting should be in line with what is detailed with the document.

3.1.3 Existing buildings may have been built during a time when less onerous Building Regulations were in force and / or may not have been correctly built to the Building Regulations at the time. It is to be noted that in both instances buildings could be assessed as having a tolerable risk in terms of Risk to Human Life. The assessor should utilise PAS 9980 to make an informed expert assessment of whether the EWS has a low, medium or high risk and direct from this if the current build up is tolerable, and no further remediation is required, or the risk is intolerable and therefore remediation should be undertaken.

3.1.4 Prior to the ban on combustible cladding material in The Building (Scotland) Amendment Regulations 2022, combustible materials within the EWS were allowed on residential buildings over 11 metres if fire test data was provided. The fire test required the EWS to be replicated, as an exact reflection of what was to be constructed on site, on a testing rig within a laboratory. The EWS would undergo a fire test in line with BS 8414, and the results of this fire test would be assessed against BR 135 criteria, design methodologies and fire spread performance to determine whether the EWS achieved a pass or fail. Although this pathway to compliance has now been removed for new residential use buildings with a topmost habitable storey above 11m, it can be used as a suitable benchmark for an Assessor to deem an EWS as tolerable if BS 8414 test data is available, and the wall build up is a true reflection of the fire test sample.

3.1.5 All types of EWS should be assessed by an Assessor in regard to their Risk to Human Life. However, it is noted that not all types of EWS pose the same inherent risk as others, and a suitable and proportionate approach should be applied by the Assessor. For example, where the EWS is brick and block, it may be suitable to not undertake a full FRAEW as these build ups are typically low risk in relation to fire spread. However, in this case the assessor should use professional judgement to determine that it is indeed low risk and a full FRAEW is not required. It should be confirmed that the build-up is in fact a brick and block build up, rather than relying on external appearance. It should also be confirmed that cavity barriers are provided around openings, if a fire can still spread into the cavity then this could potentially lead to a fire spreading from one compartment to another. In summary the Assessor should use their expertise, and professional judgement, to determine whether a full FRAEW is required on the each EWS present, and demonstrate by evidence the reasoning behind their considerations.

3.2 Limitations

3.2.1 There are a number of limitations to the SBA. These include:

• FRAEWs, undertaken following the PAS 9980, have the objective of identifying Risk to Human Life. Property protection is not to be considered the main focus of the assessments;
• The FRAEW is solely based on risk. The risk acceptance level is ‘tolerable’. The responsibility of the Assessor is to provide expert opinion on whether the EWS is tolerable;
• The aim of an FRAEW is not to assess the EWS against Building Regulations at the time of construction or to assess the EWS against Building Regulations at time of assessment;
• The principal aim of a FRAEW is not to address protection of firefighters undertaking their procedures however by undertaking this assessment, the safety of firefighters may be improved as the risk of rapid external fire spread is reduced;
• The FRAEW can only be based on available industry knowledge at the time of assessment. It is accepted that further information on the fire performance of external wall construction might come to light following the assessment.

3.2.2 The Assessor must make clear any constraints, limitations or caveats that will apply to the FRAEW.

3.3 Principles and Scope

3.3.1 The aim of the FRAEW is to provide a risk-based approach on each type of EWS present on the external walls of an in-scope Building. If there are different EWS present then the final report provides a holistic building assessment, considering all types of EWS present and how these can interact. The assessment is not based on achieving compliance with Building Regulations, although historical guidance documents can be used as benchmarks for risk, and the Assessor should be aware of their duties to only investigate each type of EWS from a risk-based approach.

3.3.2 At the end of the FRAEW, the Assessor will have determined whether the Risk to Human is tolerable or not.

3.3.3 As alluded to in Section 4.1(h) of PAS 9980, use of the PAS 9980 methodology is likely to give the most definitive assessment if the Assessor carrying out the FRAEW works in collaboration with other professionals, such as a building surveyor/architect and/or façade engineer, when needed.

3.3.4 During the FRAEW, in line with PAS 9980 methodology, the Assessor is to evaluate the complete EWS, i.e. each element from the internal lining of the EWS through to the external outer facing material. Assessors should align their definition of the EWS to this when undertaking an SBA. Any external specified attachments should also form part of the assessment, these are to include, but not exhaustive of:

• Balconies;
• Solar panels;
• Solar shading;
• Balcony walkways (including any decking);
• Green walls;
• Any other attachment which could present a risk of fire spread.

3.4 5 Steps of PAS 9980

3.4.1 The Assessor undertaking the FRAEW will be experienced with use of the PAS 9980 methodology. The Assessor must carry out the assessment following the 5 steps of PAS 9980 as follows and as shown in Figure 4.

Figure 4 - Figure 3 of PAS 9980 - Five Step Approach to the Basic Level of Assessment

• Step 1 - Confirm that a full FRAEW is required
• Step 2 - Gather all necessary information to complete the FRAEW
• Step 3 - Identify and group factors that are significant in determining the risk rating
• Step 4 - Consider each group of risk factors to determine their potential contribution to the overall risk
• Step 5 - Review the risk factor analysis against the benchmark success criteria to determine an outcome

Step 1 – Confirm a Full Fire Risk Appraisal of The External Wall is Required

3.4.2 A FRAEW is required in Scotland as part of an SBA to determine the Risk to Human Life for an in-scope Building. Therefore, the need for a FRAEW is triggered upon the commissioning of an SBA.

3.4.3 The initial step for an Assessor at this stage is to review the relevant information and confirm whether, or not, a full FRAEW assessment is warranted. The Assessor shall confirm if an EWS present on the building can immediately be considered as sufficiently low and tolerable via other avenues. It is recommended that Figure 4 of PAS 9980 is utilised for this, shown in Figure 5 of this specification document.

3.4.4 PAS 9980 notes that if there is evidence that the external walls have been classified to BR 135, this would generally confer that the build-up would be sufficiently low risk and tolerable, and therefore a full FRAEW wouldn’t be required, unless there are other factors that might have a negative bearing on the risk. However, if an Assessor is to propose this route as a justification for not undertaking a full FRAEW, based on evidence of a BR 135 classification, then an assessment should still be undertaken to ensure that the EWS is constructed in line with the BS 8414 fire test that led to BR 135 classification.

3.4.5 A significant issue with external wall construction is that the build-up is not always built in accordance with the approved design/construction drawings. Although BS 8414 fire testing, with BR 135 classification can only be utilised as a benchmark, the Assessor is therefore required to ensure that the EWS has been constructed as per the test details (confirmed by intrusive inspection) before dismissing a full FRAEW. Evidence of this shall be provided as part of their report findings.

3.4.6 If any variations to an EWS (from a BS 8414-1 test) are made then the Assessor may utilise BS 9414 in assessing the risk of these variations, if applicable. If this is not applicable then a full FRAEW, in accordance with PAS 9980, must be undertaken on the EWS.

Step 2 – Gather All Necessary Information

3.4.7 If a full FRAEW is required, the Assessor is required to gather relevant information on the building construction, fire strategy and the external wall construction. Including:

• The different types of external wall build-up and any attachments to these external wall build-ups as detailed in Section 3.3.3 of this document;
• Materials, components and systems which comprise the EWS of the building and their configurations. This includes type and location of cavity and fire barriers. The Assessor shall attempt to gain an understanding of how the building was meant to be constructed, before undertaking an assessment on what is actually present;
• The extent of the EWS on each elevation, whether it extends over the entire façade or whether it partially covers the building. This is key to understand when assessing the risk of fire spread beyond the compartment of fire origin;
• The building’s fire strategy. As a FRAEW is assessing existing buildings, a fire strategy might not always exist, or be available, for the building. The Assessor should use their expertise, based on the type of building and their knowledge of Scottish fire safety guidance, to determine the likely key fire safety provisions that would be incorporated in a building of that nature whilst reviewing against the actual as built construction;
• The building’s FRA, which should be undertaken as part of the SBA process, as detailed in Section 4. This will give the Assessor a greater understanding of the condition of the internals to assist in validating the overall risk posed by the EWS to human life. This is utilised in Annex F of PAS 9980 ‘Risk factors arising from fire strategy/fire hazards’.

3.4.8 If a previous SBA has been undertaken on the building, either as part of the pilot scheme or an SBA process that remained unfinished, the Assessor can utilise this document as part of his information gathering process. However, the Assessor must only use this as information and fulfil their own role in undertaking the assessment of the EWS.

3.4.9 The Assessor shall undertake a desktop review of all information available before going to site. This allows them to understand as much to as possible of what should be present within the EWS. Following this desktop review, a visual inspection of the building’s external wall construction shall be undertaken. In some cases, this includes opening up and intrusive inspection of the external walls to verify the as-built condition. The Assessor should open up a reasonable quantum of various wall types at key locations, such as:

• Floor levels. In residential buildings typically all floors should be constructed as separating floors, therefore fire barriers should be present at all floor levels. A number of these areas should be inspected;
• Separating walls. In residential buildings typically the walls separating each dwelling are constructed as separating walls therefore fire barriers should be present at the external wall junction with these partitions. A number of these areas should be inspected;
• Around the edges of the external wall cavity, i.e. windows, doors, service penetrations, top of cavity walls etc. The Scottish Building Standards Technical Handbook: Domestic notes that cavity barriers should be installed around the edges and openings of an external wall cavity. A number of these areas should be inspected.

3.4.10 The junctions, where a separating floor meets a separating wall, could also be inspected to limit the number of openings on the external leaf of the building as this is a location where vertical and horizontal fire barriers would be expected.

3.4.11 It is noted that for a traditional brick and masonry construction, fire barriers are not required to be provided to extend the line of fire resistance of separating wall and floor junctions into an external wall cavity. This is only applicable if the external wall is formed by two leaves of masonry or concrete at least 75mm thick and cavity barriers are provided around the edges of the cavity. Where this condition is verified on site, then the Assessor should focus their investigations on the openings in the external wall (windows, doors, service penetrations, head of cavity wall etc.) to confirm cavity barriers have been appropriately installed around the openings.

Step 3 Identify and Group Factors That Are Significant in Determining the Risk Rating

3.4.12 During this step the Assessor undertaking the FRAEW shall use PAS 9980 to determine the risk factor posed, by the external wall, on occupants of the building. The assessor will use the knowledge of the EWS, gained in Step 2, and go through the risk elements laid out in PAS 9980 to arrive at a final risk conclusion.

3.4.13 The Assessor is expected to run through each element of the following PAS 9980 Annexes and determine whether there is a Positive, Neutral or Negative risk:

Annex F – Risk factors arising from fire strategy/fire hazards (including SFRS information)

3.4.14 The influence of factors relating to the fire strategy could be:

Positive – This is to be used when a fire strategy element is deemed by the assessor to provide a significant benefit to the ability of the occupants to either: escape if fire spreads; or remain safely in the building.

Negative – This is to be used where the element is promoting the potential for harm to occupants due to preventing occupants from remaining in the building safely or escaping in time if fire were to spread via the external wall to other parts of the building.

Neutral – This is to be used where the influence is neither positive or negative or is within normal expectations for a building of this nature.

3.4.15 Assessors are to be aware that a number of fire strategy elements cannot achieve a ‘Positive’ and can only fall into ‘Neutral’ or ‘Negative’ risk factor based on whether the element meets standard guidance for the type of building or not.

3.4.16 PAS 9980 states that inherent in such an analysis is the weighting of these factors that can be applied, not always in a quantifiable manner but, nevertheless, by qualitative judgement as to their relative impact on the likelihood of people remaining in, or escaping from, the building safely.

3.4.17 Table F.1 of Annex F of PAS 9980 – ‘Risk factors arising from the fire strategy/fire hazards (including limitations of SFRS intervention’ are illustrated in Appendix E of this specification document.

Annex K – Fire performance risk factors

3.4.18 The influence of factors (relating to the fire performance of the materials, components and systems and their configurations within the EWS) could be

Positive – The fire performance limits, significantly, the scope for rapid fire spread;

Negative – The fire performance would exacerbate a fire or promote fire spread;

Neutral – Neither a positive or negative, e.g. a fire performance that allows fire spread within normal expectations.

3.4.19 The information this assessment is based off should have been gathered by the assessor in Step 2 of a PAS 9980 assessment, with the information then confirmed, or not, on site during the site visit and inspection. Where datasheets, exact product information etc. are not available the Assessor shall use their expertise to make best professional judgement on the rating for each risk factor of the fire performance for each element. Annex I of PAS 9980 provides further guidance on information gathering and Annex L provides guidance on the generic properties of external wall materials.

3.4.20 Table K.1 of Annex K of PAS 9980 – ‘Fire performance risk factors’ is shown in Appendix F of this specification document.

Annex N – Façade configuration risk factors.

3.4.21 The influence of factors relating to the configuration of the facades and the extent and location of combustible materials in the external wall typologies:

Positive – The scope of a secondary fire, resulting from fire spread, is limited significantly by the configuration.

Negative – The scope of a secondary fire is notably exacerbated or promoted by the configuration of the external wall.

Neutral – The influence is neither definitely positive or definitely negative, the characteristic of this element results in scope for secondary fires to occur within normal expectations and are therefore deemed neutral in this respect.

Step 4 - Determine Each Group of Risk Factors and Their Contribution to Overall Risk

3.4.22 During this step the Assessor shall use their expertise to consider the influence of each positive, negative and neutral risk factor determined in Step 3 to outline an overall risk rating of the EWS.

3.4.23 It should be noted that Step 4 is not an attempt to introduce quantification to the assessment. If there is a large number of either positive, negative or neutral elements then this does not define the end result and an assessor should be able to make a judgement on what elements are more highly weighted than others and may have a greater impact on the risk.

3.4.24 This step should be undertaken for each EWS present on the building if there is more than one present.

3.4.25 Table N.1 of Annex N of PAS 9980 – ‘Façade configuration risk factors’ is shown in Appendix G of this specification document.

Step 5 – Determine Outcome

3.4.26 At Step 5 the Assessor is required to take the findings from Step 4 and establish the overall risk of the building. The methodology for this, as shown in Figure 6 of PAS 9980 is that the base level of the risk is on the highest side of ‘High’. The Assessor shall work from this point, using the risk factors of each group and each element to move along the risk scale.

3.4.27 The assessor shall assess the 4 benchmark criteria stated in PAS 9980 Clause 7, determining whether these have been achieved, or not, these are:

• The likelihood of undue speed of fire spread over the external walls of the building;
• The likely consequences, namely the resultant occurrence and extent of secondary fires on other floor levels;
• The likely consequences in terms of evacuation before the onset of untenable conditions (tenability criteria in the context of a fire-engineered solution are usually based on factors such as temperature, visibility, toxicity and levels of radiant heat.) in the escape routes, whether evacuation is intended to occur immediately on the warning of fire or, in the case of a stay put strategy, at some point during the course of the fire;
• The likelihood of effective intervention by the SFRS at a point before all of the above occur.

3.4.28 First, the Risk Factor elements of Annex K – Fire Performance is taken into consideration, and second, Annex N – Façade Configuration and then Annex F – Fire Strategy/Fire Hazards. As previously stated, for Annex F to have a positive risk factor outcome, the Assessor should be ensured that any issues arising from the FRA of the SBA are to be rectified.

3.4.29 PAS 9980 notes that as a baseline, the highest risk of external fire spread on the risk scale is extremely rapid fire spread seen in the fire at Grenfell Tower.

3.4.30 PAS 9980 states that the process of positioning on the scale is subjective and requires professional judgement by a competent Assessor to determine the final position on the risk scale.

Next Step

3.4.31 Following Step 5 a conclusion on the Risk Factor of the external wall (or each EWS present) has now been determined and the next steps are as follows, based on outcome:

• ‘Low’ Risk – No requirement for any form of remedial action given the ‘low’ likelihood of fire spread and low risk to human life posed to occupants.
• ‘High’ Risk – Requirement for remedial actions to be undertaken given the ‘high’ risk to occupants and of fire spread. The Assessor should give expert opinion on what is to be remediated to lower the risk from ‘High’ into ‘Medium’ and to a tolerable level of ‘Medium’ risk.
• ‘Medium’ Risk – In the cases where neither a ‘high’ or a ‘low’ risk can be determined, the appraisal of fire risk shall seek to determine which of the following could be concluded:
  • External fire spread is likely to be more rapid than normally expected however, the heightened risk of external fire spread is tolerable in terms of risk to human life based on the methodology in PAS 9980, taking into account the consequences; or
  • The above cannot be confirmed and therefore the Assessor should determine the value of conducting a more in-depth technical assessment such as one based on fire engineering analysis or testing in order to establish a more definitive risk rating.

3.4.32 For the latter of the above, the Assessor is to give their expert opinion on the exact requirements for moving forward with a further assessment. The goal of a further assessment is to ensure that remedial actions are not to be undertaken unnecessarily if the desired outcome of the further assessment is reached, allowing the Assessor to determine a tolerable risk.

3.4.33 Section 15 of PAS 9980 ‘Scope and format of FRAEW report’ shall be adhered to, in full, by any Assessor undertaking a FRAEW. This provides the end client, and any other relevant person reading the document, with a clear report stating how the Risk to Human Life was determined and the next, recommended steps.

3.5 Post FRAEW Process

3.5.1 A FRAEW is a report that is subjective in nature. This is due to the outcome of risk being down to a large number of factors, fire performance elements with different weights and the final risk being a scaled outcome. Therefore, as part of the SBA process a peer review must be undertaken on the FRAEW to achieve agreement between two competent Assessors. The aim of the peer review is to assess whether or not the author of the FRAEW has completed their assessment in line with this SBA specification document.

3.5.2 A review of the FRAEW must be completed by an Assessor who meets the competency requirements set out in Section 2.8 for undertaking a FRAEW. At the end of this process the two Assessors will have to come to an agreement on what remedial action is required, if any, on the EWS of the building.

3.5.3 In the instance where two competent assessors have a divergence of professional opinion, it is the SBA commissioner’s responsibility to take the SBA report findings and the two Assessors through their contractually agreed dispute resolution methodology.