Cladding Remediation Programme: Single Building Assessment specification

Appendix D. Case Studies

The following case studies are fictional and are intended solely for the purpose of illustrating the application of the framework and rationale set out in this specification document. They are set out not to provide, or be relied upon as, generic solutions to the particular forms of EWS, which, by virtue of the principles within this specification document and PAS 9980, can only be considered in the particular circumstances of the building under appraisal and by taking into account all relevant risk factors. Similarly, the example discussion for the internal elements of the buildings are solely for discussion and do not provide dedicated solutions to issues that assessors may come across when undertaking an SBA. The internal areas of a building must be assessed in accordance with PAS 79-2 methodology and this appendix is not to be relied on by assessors.

Case Study 1: Four-Storey block of flats with high pressure laminate (HPL) panels and polymeric foam insulation.

Background

The building falls under the Cladding Remediation Bill as:

• Is a flatted building as defined in section 16(4) of the Land Registration etc. (Scotland) Act 2012;
• The topmost habitable storey is above the 11m threshold at 12.2m in height from ground level;
• The upper floors contain solely flats, with a number of flats also on Ground Floor alongside a Commercial Unit;
• It was built in 2000;

Therefore an SBA has been commissioned for the building.

The total number of flats within the building is 24. The residential areas of the building are typical of one with a stay put strategy, i.e. no communal fire detection and alarm system with each dwelling having its own local fire warning arrangement comprising of smoke and heat alarms. Upon detection of smoke or heat, the sounders in the flat will activate in the flat of origin only, and only occupants in that flat are required to evacuate. There are smoke detector heads within the common stair corridors to activate the AOV’s present in the corridors and at the head of the stair that aims to protect the single escape stair.

Internal Building Conditions

An assessor undertook the FRA element of the SBA on the building’s internal fire safety conditions. This focused on the common areas of the building along with the Commercial Unit on the Ground Floor. It was noted to the assessor by the Commercial Unit’s management that an FRA, undertaken to comply with Scottish Legislation, was undertaken 2 months previous. However, the assessor informed them that a separate FRA must be undertaken as part of the SBA process and this does not intervene with their requirement to commission a future FRA in around 10 months time, 12 months from the previous.

The assessor began by undertaking a Stage 1 FRA in the residential areas of the building which focused on the common corridors, stairs, plant rooms, ground floor bin store. This is a non-intrusive survey. The flat owners of the building did not have a committee and there was no way to contact a single entity who would be considered a single ‘Building Owner’ or ‘Responsible Person’. Therefore, no information on the building’s fire strategy could be obtained and the competent assessor used his knowledge to ascertain the information previously stated, a stay-put evacuation strategy, typical in residential buildings. This evacuation strategy requires a high level of compartmentation to be provided between flats and all other areas, both horizontally and vertically. The smoke detection within the common corridors and the AOVs could be spotted in the building and therefore this was assumed as the smoke ventilation system to protect the single escape stair.

During the assessment the compartmentation and fire stopping throughout the residential common areas was overall good, with only some minor issues. On the day of assessment the assessor could not make contact with any residents to check their flat entrance door, however, it was observed that a number of these doors now had letterboxes installed which would make the fire rating of the door redundant in a fire scenario. This was noted by the assessor. The assessor was able to check the stair doors and these were not in a good condition given years of wear and tear.

The assessment of the Commercial Unit focused on the interaction of this area and the residential areas. There was no shared means of escape internally. The assessor could view above the ceiling tiles that there appeared to be a lack of fire stopping where pipes penetrated the separating floor between the commercial and residential areas.

Outcome of the FRA

On the basis of the above the assessor was able to make the following recommendations to the client:

• Residential Areas – The fire doors should be made good, where letterboxes have been installed on doors then these doors are required to be removed and replaced with a compliant fire door;
• Commercial Areas – It was recommended that any penetrations through the separating floor, to the residential areas above, are fire stopped in accordance with Scottish Technical Handbook.

These are both items deemed an intolerable risk to human life by the assessor.

External Wall Construction

The whole building is covered in the HPL panels and the building only has this one EWS. All windows opened onto the cladding, including the windows of the staircase and common corridors.

The knowledge regarding the build-up of the walls was good as the as-built drawings were retrieved by the assessor and in good condition. The information suggested that there was lightweight SFS walls spanning the concrete slab floors, onto which there was an external wall build up comprising a 9mm Class B cement particle sheathing board, a layer of 80mm of phenolic foam insulation of a type specifically formulated to enhance its behaviour in fire, a 50mm cavity and facings of 9mm Class B HPL panels, referred to as so-called “FR grade” panel.

The competent assessor was aware that combinations of HPL and combustible insulation are considered as potentially presenting a similar risk to unsafe systems using Category 3 ACM. On this basis, without further consideration, they informed the client that it would be highly likely that the outcome of the basic level of an FRAEW assessment would be to give the walls a “high” risk rating.

A further consideration of the “high” risk rating was the extent of the use of this EWS, covering the whole building as well as being adjacent to escape routes. Therefore, this could not reduce the risk rating.

However, the competent assessor was aware of the BS 8414 test evidence of a very similar combination of Class B HPL panels and the particular type of foam used. Although, in that particular case, it did not fully meet the acceptance criteria in BR 135 for it to be classified, the test revealed that temperatures exceeded 600°C by only 50°C, with no flaming above the top of the testing rig.

Therefore, further assessment was required on the EWS to gain a more in-depth understanding of the fire performance of the wall build-ups on the building and the fire risk this posed. As the building was constructed in the year 2000, it was important to check the as-build construction to see if it was up to a good standard.

Findings From Investigations

Intrusive inspections were required on the EWS with a focus on confirming the make and manufacturer of the materials and products used and verifying the wall build up to make sure it was built in accordance with the as-built details. Samples were to be taken at a number of separating wall and floor junctions, to focus on the fire barrier provisions, along with sampling taken around a number of openings i.e. windows and doors.

Site investigations revealed that product substitution had taken place and that, in a number of aspects, the walls differentiated from the as-built drawings and thus the anticipated build up. This included:

• The HPL panels were from a different manufacturer and, from labelling present, the exact product could be confirmed and from the datasheet, retrieved from the manufacturer’s website, this was a Class D product in the manufacturer’s “standard grade” range;
• The insulation was 100mm PUR foam (Class E);
• The cavity was narrower; and
• The HPL panels were supported on a timber structure and not on metal brackets.

The site investigations showed that fire and cavity barriers had been in installed correctly, in accordance with the as-built drawings which were in accordance with guidance at the time of construction.

Outcome of the analysis of the risk and possible remedial action

On this basis, the external wall assessor was of the opinion that the actual EWS was so far removed from any form that they knew had been tested that further in-depth technical assessment was unlikely to be capable of refining the risk; the overall conclusion that the walls fell within the “high” risk rating band was supported further by the investigation.

Accordingly, the assessor made the following recommendations:

• Unduly rapid external fire spread was highly likely, even despite the full and effective cavity barrier protection in place;
• It was possible that occupants would be exposed to significant harm from secondary fires before escaping or be prevented from escaping, given the speed with which fire and smoke could spread;
• It was also possible that the communal means of escape would be compromised before occupants could safely use them to escape, because of the ease and speed with which rapid fire spread could impinge on staircase windows; and
• The rate of fire spread could readily be such as to limit the scope for the SFRS to intervene effectively.

Accordingly, remedial action was considered necessary to address the risk, and removal and replacement of the cladding system, in its entirety, was the most appropriate means to achieve this given the extent of the issues. The external wall assessor advised the client to notify the SFRS of the risk.

The FRAEW assessor also took cognisance of the FRA, however, given the extent of the issues of the EWS, the conditions of the internal elements of the building was not considered as a further negative factor for the EWS.

Post Assessment

The FRAEW element of the SBA was reviewed by a secondary, independent, competent assessor. This secondary assessor’s main aim is to ensure that the initial assessor undertook the FRAEW in accordance with PAS 9980 methodology. The secondary assessor agreed that given the extent of issues present within the EWS that a full replacement is required.

Upon the client informing the SFRS about the risk of the external wall, it was agreed that a waking watch will be implemented until the remedial actions are completed or, in accordance with the National Fire Chief’s Guidance, until a simultaneous evacuation strategy and alarm system is installed. This is aiming to increase occupant safety during this time.

A design team was then brought together by the client to detail out the design of the new EWS. As this is considered as ‘Major Works’ under Scottish Legislation the works fall under Schedule 3 of The Building (Scotland) Regulations 2004.

Upon completion of the remedial actions, the assessor who undertook the initial FRAEW will reassess the replacement EWS, using as built drawings and photos undertaken through the construction of this. If the assessor views the new EWS as a low or tolerable risk then this will be stated in the SBA and it will be placed on the Cladding Assurance Register.

Case Study 2: Six Storey block of flats with Brick and Block EWS.

Background

The building falls under the Cladding Remediation Bill as:

• Is a flatted building as defined in section 16(4) of the Land Registration etc. (Scotland) Act 2012;
• The topmost habitable storey is above the 11m threshold at 18.4m in height from ground level;
• The scheme contains solely flats;
• It was built in 1996;

Therefore an SBA has been commissioned for the building.

The total number of flats within the building is 42. The evacuation strategy of the building is typical for that with a stay put strategy, i.e. no communal fire detection and alarm system with each dwelling having its own local fire warning arrangement comprising of smoke and heat alarms. Upon detection of these the sounders in the flat only will activate and only that flat will be required to evacuate. There are smoke detector heads within the common stair corridors to activate the AOV’s present in the corridors that aims to protect the single escape stair.

Internal Building Conditions

An assessor undertook the FRA element of the SBA on the building’s internal conditions. This focused on the common areas of the building.

The assessor began by undertaking a Stage 1 FRA to PAS 79-1 methodology in the common areas of the building, utilising the FRA template in Appendix C of this specification document, this focused on the common corridors and stairs. This is a non-intrusive survey. The assessor was able to get in contact with one of the residents and the assessor was made aware that there was a residents committee. Upon questioning the committee the assessor was made aware that the residents were not aware of their responsibility under the Fire Safety (Scotland) Regulations 2006 for the maintenance of fire safety measures for the protection of firefighters. The committee also were not able to provide any further information to the assessor regarding fire safety information (a fire strategy, maintenance records, alarm commissioning records etc.). The committee member was able to inform the assessor that there was a minor fire in a flat on the First Floor in 2021 and fire did not spread into other areas of the building however, some smoke had spread into the First Floor common corridor and had activated the AOV at the end of the corridor. The competent assessor used his knowledge to ascertain the information previously stated, a stay-put evacuation strategy, typical in residential buildings, is provided. This evacuation strategy therefore requires a high level of compartmentation to be provided between flats and all other areas, both horizontally and vertically. The smoke detection within the common corridors and the AOVs could be spotted in the building and therefore this was assumed as the smoke ventilation system to protect the single escape stair.

During the assessment the assessor witnessed a number of fire stopping details either unfit for purpose or seemingly no effort had ever been made to provide fire stopping. This was apparent in a number of key areas including at the partitions between the common corridors and the single stair and between the common corridors and the flats. Through finding out information from the committee the assessor was able to focus on the First Floor flat that had a fire scenario in 2021 and there was a lack of fire stopping of the penetrations running into the flat from the common corridor which may have caused the smoke to spread into the corridor, as had been mentioned.

The assessor was also able to view a sample of flat entrance doors and these had shown significant wear and tear with a number missing smoke seals and a further number having excess gaps around the doors. The doors into the stair also showed significant wear and tear with the doors at Second and Fourth Floor not fully closing due to the self-closers being faulty.

Outcome of the FRA

On the basis of the above the assessor was able to make the following recommendations to the client:

• Fire Doors – The flat entrance doors should all be checked and made good where defects are evident. They should all have smoke seals and the gaps present around them should not exceed those in the manufacturer’s installation guidance. The doors into the stair also need to be made good and the self-closers of these fixed were they are no longer suitable for work;
• Fire Stopping – The assessor recommended a ‘find and fix’ solution to the fire stopping issues within the building, given the extent of the issues present.

These are both items deemed an intolerable risk to human life.

External Wall Construction

The whole building, from the external, appears as brick. The assessor assumed initially that this would be a brick and block build up and was then able to confirm this with further investigation. The assessor is aware that not all brick and block build ups require a full FRAEW if it can be confirmed that the cavities are suitably fire stopped to prevent fire spread to other areas of the building. Therefore an assessment was undertaken around the openings in the common areas for cavity barriers.

Findings From Investigations

Upon further inspection of a number of windows, doors and service penetrations no cavity barriers were present around any of these openings inspected. The insulation present did also not appear to be of limited combustibility given the manufacturer’s name and the year the building was constructed. Therefore, the assessor knew a further assessment was required in the form of a full FRAEW.

The assessor was able to mark up key locations for intrusive inspection of which cavity barriers could potentially be located in the external wall build up, i.e. where flat walls meet the external wall and were the separating floors of flats also meet the external wall.

During the intrusive inspection there were no cavity barriers found. Therefore a fire breaking into the cavity via an opening, i.e. window or door, could easily spread via the cavity to other flats given the combustible insultation present.

Outcome of the analysis of the risk and possible remedial action

On this basis, the external wall assessor was of the opinion that the EWS was a ‘high’ level of risk to human life given how easily a fire could spread from one flat to another.

Accordingly, the assessor made the following recommendations:

• Unduly rapid external fire spread was highly likely if a fire broke into the cavity which could happen due to no cavity barriers present around windows;
• It was possible that occupants would be exposed to significant harm from secondary fires before escaping or be prevented from escaping, given the speed with which fire and smoke could spread;
• It was also possible that the communal means of escape would be compromised before occupants could safely use them to escape, because of the ease and speed with which rapid fire spread could impinge on staircase windows; and
• The rate of fire spread could readily be such as to limit the scope for the fire and rescue service to intervene effectively.

Accordingly, remedial action was considered necessary to address the risk, and the assessor recommended that cavity barriers were installed around all openings in the external wall. The external wall assessor advised the client to notify the SFRS of the risk.

The FRAEW assessor also took cognisance of the FRA, noting the extent of issues present within the areas. Although these are to be made good by the client as they are items deemed an intolerable risk to human life, this can take months to remediate. Therefore, the assessor proposed that the alarm and detection system present within the building was reconfigured so that detection anywhere in the building leads to a simultaneous evacuation.

Post Assessment

The FRAEW element of the SBA was reviewed by a secondary, independent, competent assessor. This secondary assessor’s main aim is to ensure that the initial assessor undertook the FRAEW in accordance with PAS 9980 methodology. The secondary assessor agreed that cavity barriers should be provided around openings to lower the likelihood of fire breaking into the cavity. The secondary assessor also mentioned that they would like to see the insulation replaced with a non-combustible alternative but as the initial assessor had undertaken the FRAEW suitably in accordance with PAS 9980 they agreed with the initial assessor’s recommendations.

Upon the client informing the SFRS about the risk of the external wall, a M&E alarm specialist was brought into reconfigure the alarm to a simultaneous evacuation.

A design team was brought in by the client to detail out the remedial actions that are to be undertaken both externally and internally.

Upon completion of the remedial actions, the assessor who undertook the initial FRAEW will reassess, using as-built drawings and photos undertaken through the process of the cavity barriers being provided. Given the extent of the issues that needed to be remediated internally, a secondary assessment of these areas was undertaken by the initial FRA assessor to ensure that their actions had been suitably remediated. If these works had been undertaken as recommended in the assessment then the building will now be deemed as a low or tolerable risk. This will be stated in the SBA and it will be placed on the Cladding Assurance Register.

Case Study 3: Nine Storey block of flats with areas of Terracotta tile facing external leaf but mainly a brick slip system.

Background

The building falls under the Cladding Remediation Bill as:

• Is a flatted building as defined in section 16(4) of the Land Registration etc. (Scotland) Act 2012;
• The topmost habitable storey is above the 11m threshold at 27.2m in height from ground level;
• The upper floors of the scheme consists of solely flats and residential amenities such as a gym and lounge room on Ninth Floor. The Ground Floor consists of solely non-residential areas such as Bin Stores and Plant Rooms;
• It was built in 2018;

Therefore an SBA has been commissioned for the building.

The total number of flats within the building is 90. The evacuation strategy of the building is typical for that with a stay put strategy, i.e. no communal fire detection and alarm system with each dwelling having its own local fire warning arrangement comprising of smoke and heat alarms. Upon detection, only the sounders within the flat of origin will activate and only the occupants within that flat will evacuate. There are smoke detectors present within the common stair and corridors to activate the mechanical smoke control system present.

Internal Building Conditions

An assessor undertook the FRA element of the SBA on the building’s internal fire safety measures. This focused on the common areas of the building.

The assessor began by undertaking a Stage 1 FRA to PAS 79-1 methodology in the residential areas of the building, utilising Appendix C of this specification document, which focused on the common corridors and stairs. This is a non-intrusive survey. When the assessor arrived on site it was clear that the building’s internal fire safety measures were satisfactory. It was confirmed by a resident that upon the building opening in 2018 a number of residents understood their duties under the Fire (Scotland) Act 2005 and contracted services to a property manager who undertakes inspection and maintenance as/when required. All information that the residents had on the building’s internals was passed to the assessor. The assessor was able to confirm a stay-put evacuation strategy is in place which means that if there is a detector activated in the corridor then a manned outstation is notified of the alarm and the SFRS is contacted. Therefore, this evacuation strategy requires a high level of compartmentation to be provided between flats and all other areas, both horizontally and vertically. All records showed that the communal fire alarm systems, fire doors and smoke control systems were checked every 18 months so far.

During the assessment, the assessor witnessed minor fire stopping issues within service risers and the fire stopping was missing between the plant room and bin store areas. All firestopping on the residential levels looked to be provided and installed in accordance with guidance and manufacturer’s details.

Out of the 15 apartment doors sampled only one appeared to show wear and tear with a smoke seal missing. All communal doors still appeared to be in good condition with all self-closers working accordingly, where assessed.

Outcome of the FRA

On the basis of the above the assessor was able to make the following recommendations to the client:

• Fire Doors- Going forward these should be continually reviewed but currently on the whole appeared to be still in good condition;
• Fire Stopping – It is recommended that firestopping is provided between the plant room and bin store and fire stopping in risers is made good.

The assessor did not consider these as items that could be considered intolerable risk to human life when taking into consideration risk to occupants via the EWS.

External Wall Construction

The building appears externally to consist of 7 storeys of a brickslip system and then the top two storeys are a system which contains a terracotta external leaf. Given the recent completion of the building, the architects of the building were able to send the Scottish Government the drawings who were able to forward this on to the assessor. The drawings confirmed the above coverage of each EWS system, with all primary materials being non-combustible (Class A1/A2).

The assessor could not depend on the drawings to confirm the exact build up, therefore intrusive inspections were to be made on both EWSs. The chosen areas were around a sample of window and door openings and at a number of junctions of separating walls and floors with the external wall.

Findings From Investigations

During the inspection of the brickslip system it appeared initially that it had been built in accordance with the Architectural drawings. However, upon closer inspection the assessor noted where fire barriers should be present at separating walls and floors junctions, a cavity barrier product had been used instead. A similar solution was used around the openings. Given the height of this building the fire barrier present in these areas should achieved a 90/90 fire resistance for integrity and insulation if built in accordance with guidance. The cavity barrier product achieved 30/15 minute fire resistance.

In the Terracotta system all cavity and fire barriers were provided in accordance with the Architectural drawings, which aligns with guidance. However, the insulation provided behind the Terracotta tiles was a Class C product and not non-combustible as shown in the drawings. The rest of the system was built as it should have been.

Outcome of the analysis of the risk and possible remedial action

The assessor was aware that both EWS systems were not built in accordance with the initial design drawings.

The brickslip system did not have 90/90 fire barriers installed where the separating floors and walls met the external wall. However, given that the insulation surrounding these was a non-combustible material and that the cavity barriers still provided a reasonable level of fire resisting separation at these junctions, with a non-combustible outer leaf, it was deemed that fire spread via the EWS was low risk.

The terracotta system has Class C insulation installed where a non-combustible insulation should be provided. This system only covered the top two storeys of the building and all other key materials present were non-combustible, including the outer leaf, with 90/90 fire barriers provided at all separating walls and floors and cavity barriers provided around all openings. The assessor noted that a fire may result in ignition of the insulation if it broke into the EWS, but given the fire barriers provided it was unlikely to spread further than the flat of fire origin via the EWS. The assessor used their judgement on proportionality to determine that remedial actions would not be required to replace the insulation.

The FRAEW assessor also took cognisance of the FRA and the lack of issues present reinforced the low and tolerable level of risk concluded.

Post Assessment

The FRAEW element of the SBA was reviewed by a secondary competent assessor. This secondary assessor’s main aim is to ensure that the initial assessor undertook the FRAEW in accordance with PAS 9980 methodology. The secondary assessor agreed that in the brickslip system the cavity barriers provided should limit fire spread to other flats via the external wall and no remedial action was required in this system.

The secondary assessor, however, did show their concern with the presence of a Class C insulation product in a building of this height. However, they accepted that the initial assessor took on board the location of this EWS and agreed that given the non-combustibility of the terracotta tiles that the insulation present would be a tolerable risk to human life.

As no further remedial action was required, the party who commissioned the SBA then began the process to include the building on the Cladding Assurance Register.