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Grenfell inquiry report condemns cladding refurbishment

30 Oct 19 The first report of the official inquiry into the Grenfell Tower fire has now been published, with urgent lessons for the construction industry and building materials firms as well as the London Fire Brigade.

The Grenfell Tower fire killed 72
The Grenfell Tower fire killed 72

Today’s report is the conclusion of phase one of the inquiry led by Sir Martin Moore-Blick, which focuses primarily on the events of 14th June 2017, how the fire started in the west London tower block and how the emergency services responded.

The report explains in great detail the refurbishment of the tower block that completed in 2016. It was the choice of cladding insulation materials, how they were combined and how they were installed that led to the fire spreading so quickly, leading to 72 lives being lost.

The fire brigade’s policy of telling residents to stay put was also a contributing factor.

Phase two of the inquiry, starting in January, will really put the parties involved in the refurbishment under the microscope, and indeed the whole UK construction industry leadership involved in the setting and policing of standards.

The fire was started by an electrical fault in a large fridge-freezer in the kitchen of Flat 16, for which the resident bears no blame, Sir Martin says.

“I have not been able to establish the precise nature of the fault in the fridge -freezer, but consider that to be of less importance than establishing how the failure of a common domestic appliance could have had such disastrous consequences," he writes. "The fire is most likely to have entered the cladding as a result of hot smoke impinging on the uPVC window jamb, causing it to deform and collapse and thereby provide an opening into the cavity between the insulation and the ACM cladding panels through which flames and hot gases could pass. It is, however, possible (but less likely) that flames from the fire in the fridge-freezer passed through the open kitchen window and impinged on the ACM cladding panels above.”

Sir Martin Moore-Blick writes in the phase one report: “There was compelling evidence that the external walls of the building failed to comply with Requirement B4(1) of Schedule 1 to the Building Regulations 2010, in that they did not adequately resist the spread of fire having regard to the height, use and position of the building. On the contrary, they actively promoted it. It will be necessary in Phase 2 to examine why those who were responsible for the design of the refurbishment considered that the tower would meet that essential requirement.”

He says that “there are grounds for thinking that the current regime for testing the combustibility of materials and cladding systems, particularly those chosen for use in high-rise buildings, may be neither as rigorous nor as effectively enforced as it should be”.

He also says, in effect, that building contractors can no longer take at face value the claims made by product manufacturers. One of the lessons of the Grenfell Tower fire, Sir Martin suggests, is that building products may not be as good or effective as their manufacturers claim.

He writes: “Doubts have also arisen about the reliability of the certification of certain materials for use in high-rise buildings. Grave concern inevitably arises simply from the fact that it was possible for highly combustible materials to be used for the purposes of refurbishing and cladding a building like Grenfell Tower. How that was possible is a question that may be relevant to many aspects of the construction industry, including manufacturers of products currently widely available on the market. Pending further investigation it would clearly be sensible for anyone who is responsible for the fire safety of an existing building or who is considering the use of products on high-rise buildings to scrutinise the information about them provided by the manufacturers and exercise considerable care to ensure that they meet the required standards.”

Sir Martin also adds his voice to concerns that have already been widely voiced about the scandalously slow progress in replacing similarly lethal cladding systems on other tall buildings around the country.

He writes: “It is clear that the use of combustible materials in the external wall of Grenfell Tower, principally in the form of the ACM rainscreen cladding, but also in the form of combustible insulation, was the reason why the fire spread so quickly to the whole of the building. Surveys undertaken since the fire have established that external wall materials similar to those used on Grenfell Tower have been used on over 400 other high-rise residential buildings around the country. From the evidence put before me in Phase 1, two very important matters have come to light: first, that in its origin the fire at Grenfell Tower was no more than a typical kitchen fire; second, that the fire was able to spread into the cladding as a result of the proximity of combustible materials to the kitchen windows. It is not possible to say whether the same or a similar combination of design and materials is to be found on any other buildings, but it would be sensible for those responsible for high-rise buildings with similar cladding systems, if they have not already done so, to check whether the same or a similar combination exists. However, even if they do not, fires can occur in a wide variety of circumstances and in cases where the exterior walls of the building include combustible materials of a similar kind, might gain access to it by a variety of different routes. It is not surprising, therefore, that people living in such buildings are concerned for their safety. It is unnecessary for me to recommend that panels with polyethylene cores on the exterior of high-rise buildings be removed as soon as possible and replaced with materials of limited combustibility because it is accepted that that must be done. It is essential that it be done as quickly as possible and concern has been voiced publicly, most recently by the House of Commons Communities & Local Government Select Committee, about the apparently slow rate of progress in carrying out the work. In the light of what has been learnt in Phase 1 about the behaviour of ACM panels with polyethylene cores when exposed to fire, I wish to add my voice to that of the committee in expressing the view that the programme of remedial work should be pursued as vigorously as possible. In view of the part played by the architectural crown in the spread of the fire at Grenfell Tower, particular attention must be paid to decorative features composed of combustible materials.”

Sir Martin Moore-Blick's report praises the courage of the fire fighters who tried to tackle the blaze but was critical of the London Fire Brigade's systemic failings, its adherence to the 'stay put' policy and apparent failure to learn lessons from the July 2009 Lakanal House fire in Camberwell.

However, the general secretary of the Fire Brigades Union, Matt Wrack, retorted: “The inquiry’s structure prioritises scrutiny of firefighters, who did everything that they could to save lives, over investigating the critical issues of public safety that led to the fire and caused it to spread in such a disastrous manner.

“Before any firefighter arrived that night, Grenfell Tower was a death trap. Firefighters that night acted bravely in impossible circumstances, many of them repeatedly risking their own lives to save others. We welcome that this is reflected in the inquiry’s report.

“The true culprits of the fire are those who wrapped the building in flammable cladding, who gutted the UK’s fire safety regime, who ignored the warnings from previous fires, and who did not hear the pleas of a community worried for their safety. We will be watching phase two of the Inquiry closely to ensure they are held to account. But we cannot wait for years for the Inquiry to conclude. Change is needed now.”

The facts relating to the 2016 refurbishment are set out in detail in chapter six of the phase one report, which we reproduce below

The most significant development, both in terms of the history of the building and relevance to the fire on 14 June 2017, was the refurbishment carried out between 2012 and 2016 (the main refurbishment). During that period Grenfell Tower underwent substantial change. The work affected both the outside and the inside of the building. Most significantly, it incorporated the over-cladding of every storey of the existing building with a new insulation and rainscreen cladding system.

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Planning permission was first sought in 2012 and a lead contractor, Leadbitter Construction Ltd, was appointed. However, after a further procurement process, in June 2014 Rydon Maintenance Limited was eventually appointed the design and build contractor.

The architect for the main refurbishment was Studio E; the Employer’s Agent and Quantity Surveyor was Artelia Projects UK Limited. The cladding subcontractor to Rydon was Harley Facades Ltd (which succeeded Harley Curtain Wall Ltd). Some specialist fire engineering services were provided during the project by Exova Warringtonfire.

The client for the refurbishment works was the Kensington & Chelsea tenant management organisation (TMO). The works were funded by the Royal Borough of Kensington & Chelsea, which released the funds for the project in May 2012. The department of building control at RBKC acted as building control authority, conducting a number of inspection visits between August 2014 and July 2016. The building certificate for completion of the works was signed by RBKC on 7 July 2016.

In addition to the over-cladding of the building, there was a full refurbishment internally of the very lowest floors from the ground floor to floor 3 inclusive, including structural works. This included the creation of nine new flats on these lower floors and the relocation and refurbishment of the existing nursery and boxing club. Soft and hard landscaping works were also carried out in the area immediately surrounding the tower.

Building services works were carried out within every floor and within every flat. The mechanical and electrical services engineer was Max Fordham (appointed by the TMO); Rydon also engaged JS Wright & Co. Ltd to carry out detailed designs and installation of the M&E works. These internal building services works included the fitting of a new heating system to all areas, the provision of a new boosted cold water distribution system and the refurbishment and extension of the existing environmental ventilation and smoke control system, together with some alterations to the lifts and dry riser system.

A central part of the main refurbishment was the addition to the tower of a ventilated rainscreen insulation and cladding system. Effectively a new external wall was created by attaching a number of components to the existing concrete facade. At floors 4 to 23 they comprised insulation materials, new windows, new window infill panels and outer aluminium composite material (ACM) rainscreen panels.

At floors 1 to 3 the outer wall was re-clad with glass-reinforced concrete castings on the columns and other types of rainscreen panels. The report focuses on floors 4 to 23 of the tower, because the lower external walls were not involved in the fire.

The outer layer of the new external facade, which covered the existing concrete spandrel panels and the columns, comprised ventilated rainscreen panels made of aluminium composite material. Before being fitted to the building the panels were fabricated into “cassettes”, i.e.three-dimensional shapes which can be hung on steel or aluminium supports fixed to the concrete structure. In general this kind of system is called a “ventilated rainscreen system” because it is designed to shelter the building from the majority of direct rainfall but has gaps which are designed to permit the ventilation of the cavity behind the panels and ensure that water is collected and drained away.

The rainscreen panels were manufactured as plain sheets by Arconic Architectural Products SAS and were fabricated into cassettes for use at Grenfell Tower by CEP Architectural Facades Ltd. The panels used on the columns and for the spandrels at floors 4 and above were known as Reynobond 55 PE Aluminium Composite Panels (ACP) and had an external finish referred to as Smoke Silver Metallic Duragloss 5000 Satin. Each panel consisted of a 3mm thick core of polyethylene bonded between two 0.5mm thick sheets of aluminium. To date, two different coloured PE cores have been found in panels fixed to the tower, one black and one translucent. Testing is being undertaken to establish whether there are any significant differences between the properties of these materials in terms of their reaction to fire.

Polyethylene is a combustible synthetic thermoplastic polymer which melts and drips on exposure to heat. It can flow whilst burning and generate burning droplets. It has a high calorific value compared with other common construction materials and will provide a fuel source for a growing and spreading fire. It melts at 130-135°C and ignites at around 377°C. On exposure to heat aluminium melts at approximately 660°C. It has a comparatively high coefficient of thermal expansion, which means that it can be expected to warp and deform under the influence of heat.

In the spandrel locations, the panels were formed with a 30° sloping return to the bottom of the window, and a 90° horizontal return to the top of the window. On all of the cut edges of the panels the polyethylene core was exposed and the polyethylene core was also exposed along the fold lines on the inside of each cassette. At the head of the window the design incorporated a 20mm gap between the panel and the window frame. The spandrel panels were hung on vertical cladding rails at approximately 1150mm centres; they were fixed to the building using steel angle pieces (at the window head and sill), brackets and cladding rails on which the panels were hung. The spandrel panels were of varying sizes depending on their locations. This is a close-up photograph of the panels on the tower.

On the columns, the cassette panels were longer in shape, each one extending from halfway up the spandrel panel below the window, to halfway up the spandrel panel above the window, as can be seen from the image above. This meant that there was a continuous panel at the junction between the windows and the column. The column panels were also fixed to the face of the concrete columns using steel angle pieces and cladding rails. The columns were clad with one panel per face, i.e. two panels for the internal columns and three panels on the corner columns. There were gaps of between 15mm and 30mm between the panels, both on the spandrels and the columns.

[Expert witness] Dr Barbara Lane has compared the cassette panels installed at Grenfell Tower with Arconic’s standard details for modular cassette panels. There are a number of differences between the Grenfell Tower panels and standard Arconic cassette panels, including the return depth of the panel, which is significantly greater on the cassettes used on Grenfell Tower. It appears that both the shape of the cassettes and the method of fixing were designed specifically for the refurbishment project.

Behind both the spandrel and the column ACM panels was a layer of insulation fixed directly to the building. On the spandrels this consisted of two 80mm layers of insulation board, either Celotex RS5000 polyisocyanurate (PIR) polymer foam or (in very limited quantities) Kingspan K15 phenolic polymer foam, depending on the particular location. On the columns, the insulation consisted of one 100mm layer of Celotex RS5000 PIR. A small number of Kingspan K15 insulation boards have also been found on the columns.

In some instances an additional piece of insulation board was located adjacent to the windows, alongside the columns, but that varied across the building. The insulation was fixed to both the spandrels and the columns by means of 180mm stakes screwed into the face of the existing concrete.

Between the inside face of the rainscreen panel and the outer face of the insulation there was a space or cavity, the width of which varied from 139mm on the columns to 156mm on the spandrels. These cavities were an integral part of the design, their purpose being to allow ventilation and the drainage of any water that penetrated the gaps between the rainscreen panels. Smaller cavities, which had no design function, were also created between the flat surfaces of the insulation boards and the ridged pre-cast biscuit facing of the columns.

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