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Grenfell Inquiry: Burning cladding overrode the building's passive fire protection

As inquiry begins hearing technical evidence, expert reports expose failings of wide range of elements from doors to windows to smoke ventilation, amidst a ‘culture of noncompliance’

The Grenfell Tower inquiry has begun to hear technical evidence, bringing expert reports that have highlighted a litany of failings, from noncompliant fire doors and smoke ventilation to a fire rescue protocol that was quickly overtaken by events on the night of June 14, 2017.

While many of these are not directly related to HVAC disciplines, they are of vital importance given the HVAC industry’s integral role within a fire-safe construction process.

No fewer than five expert technical reports were placed on the public record on Monday June 4 as the inquiry began hearing technical evidence on the causes of the fire.

Key among these reports is the submission from Dr Barbara Lane, Arup director and fire safety engineering specialist, who has assessed the outbreak of the fire from an engineering perspective.

Dr Lane’s conclusion made for a widespread condemnation of many of the assumptions at play at Grenfell, whether it be the fire safety principle of Stay Put, or the passive fire protection measures designed to keep individual flats and the stairs and lobby area protected from fire and smoke. While she highlighted the cladding and windows as major factors, Dr Lane made clear that multiple failings contributed to the extent of the fire and the consequent loss of life. 

She said: ”The construction materials forming the rainscreen cladding system, either individually or when asssessed as an assembly, did not comply with the recommended fire performance set out in the statutory guidance of Approved Document B 2013 for a building of that height…Additionally, I conclude that the entire system could not adequately resist the spread of fire over the walls, having regard to height, use and position of the building… There were multiple catastrophic fire-spread routes created by the construction form and detailing.”

However, the cladding and window installation come in for particular criticism from Dr Lane, who listed no fewer than nine consequential failings as a result. Her conclusion was that thanks to these multiple issues, the cladding was ’noncompliant with the functional requirements of the Building Regulatiions.”

She said: ”Attempts had been made to subdivide the column cavities and horizontal firestopping at key compartment lines. However, both the horizontal and vertical firestopping were installed incorrectly and no evidence has been provided that they were ever tested for performance in an Aluminium Composite Panel-based rainscreen cladding system of the type installed at Grenfell Tower.”

Her report also heavily criticised the window installations at Grenfell, which were not constructed as fire safe ‘systems’ and thus not only failed to prevent the spread of the initial fire from Flat 16, but enabled the fire to spread across the cladding, rendering the passive fire protection compartmentation ineffective.

She said: “The windows were not provided with fire-resisting cavity barriers. These unprotected openings themselves were surrounded by combustible material. Additional combustible materials were located in the room on the ceiling beside the window. Therefore, in the event of any fire starting near a window, there was a disproportionately high probability of fire spread into the rainscreen cladding system. This was also true in the event of a fire remote from the window, unless the fire brigade extinguished it…”

The combination of these windows and the cladding meant there was no control of the fire and smoke from the initial flat fire, she said, with ’the type of materials used and how they were arranged around the windows in the kitchen contribut[ing] to the speed at which the fire spread from the flat fire of origin to a multi-storey external fire.’ 

In Dr Lane’s conclusion, she singled out those involved with the design and installation of the cladding for not communicating with the fire service the fact that it was combusitible. She added: “I have found no evidence yet than any member of the design team or the construction team ascertained the fire performance of the rainscreen cladding system materials, nor understood how the the assembly performed in fire. I have [also] found no evidence that Building Control were either informed or understood how the assembly would perform in a fire.”

Dr Lane’s analysis of the fire service’s Stay Put principle also highlighted a misunderstanding of the role of the cladding. Her conclusion was that the cladding’s combustibility effectively overrode all the passive fire protection in place - and thus invalidated the assumptions of Stay Put. She said:  “Despite the flats being provided with internal compartmentation, it was not the case there was a low probability of fire spread beyond the flat of origin, because the fire was spreading through the rainscreen cladding system itself, which was connected to every flat…”

As a result, she said,  the principles of Stay Put had ’substantially failed’ by 01:26 due to the spread of fire. This, she noted was significantly earlier than the formal end to that strategy, which was not ordered by the Fire Service till 02:47.

Dr Lane also emphasised a serious lack of communication with the residents over the changed guidance, to evacuate, rather than Stay Put. She concluded: “In light of the number of other residentail buildings in the UK with a building envelope formed of similar materials to Grenfell Tower, serious and urgent consideration should be fiven to changing the current approach.”

Other failings highlighted in Dr Lane’s report include:

  1. Fire doors that had been replaced in 2011 to 106 flats were noncompliant with the statutory guidance and ’would have contributed to the failure to prevent the spread of fire and hot smoke from the flat to the lobby’;
  2. A number of these doors failed to self-close in the event of fire;
  3. Doors to the stairway may have failed to prevent fire due to noncompliance. Further evidence is required, but they may have only offered 20 minutes’ integrity fire resistance, against statutory guidance for 60 minutes;
  4. The fire prevention aspect of the doors was compromised by being held open by fire hoses;
  5. The smoke ventilation system was a bespoke system that was not in compliance with Approved Document B and did not operate as intended;
  6. The smoke ventilation system was designed only to extract smoke from one floor at a time and so would not have been capable of stopping the spread of smoke to the stairs from multiple floors;
  7. The ‘fire lift’ did not provide adequate capacity to support the fire service or to resuce occupants, forcing the fire crews to walk up and down stairs
  8. The water supply was insufficient for fire service use, with the dry fire main non-compliant with both guidance at the time of the building’s design and current regulations. The latter regulations require it to be located at the stairway, rather than its actual location at the lobby. A wet fire main, Dr Lane concluded, could have allowed a quicker response to the initial outbreak of fire in Flat 16, although it is not guaranteed to have prevented the spread of fire.

These failings led Dr Lane to suggest that ’the number of non-compliances signify a culture of noncompliance at Grenfell Tower. I am particularly concerned about the maintenance regime of the active and passive fire protection measures. I note that multiple automatic systems such as the control of the fire lift and the smoke ventilation system, appear not to have operated as required.’

The report is intended to be followed by a second phase, during which Dr Lane will seek further evidence of cause and effect and make specific recommendations. As part of her general recommendations for phase one, she highlighted a widespread lack of understanding of the appropriate fire testing evidence required for materials used, from the cladding to the fire doors. She said: “I have found no evidence that this was understood by relevant professionals, prior to handover of the fire safety system, nor was it understood by the fire safety management regime. In my view it is essential that there is renewed and proper understanding of relevant test evidence and how it relates to performance, as already emphasised in Approved Document B 2013. This is a critical change which is needed throughout  the design and construction industry.”

She also called for further investigation into the gas installations, both in terms of compliance and whether it could be isolated within a reasonable time on the night of the fire.

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