Why Did This Fire At An English Tower Block With Combustible ACM(LD-PE) Cladding Lead To The Horrific Grenfell Tower Inferno?

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Why Did This Fire At An English Tower Block With Combustible ACM(LD-PE) Cladding Lead To The Horrific Grenfell Tower Inferno?

[ Posted by Lara Keller 2/11/19 Updated 8/11/19] anchorTableSmall - Copy Blog Table Of Contents

Continuing articles on the terrible Grenfell Tower Fire of 14th June 2017 in London. This one focuses on the truth that the ACM cladding fire at Grenfell Tower in England, was one of many similar fires in tower blocks with similar combustible cladding in England. If the conclusions of the Grenfell Inquiry’s Phase One Report are correct, and the wide spread interpretation of the UK BRE tests in 2017 on different combinations of ACM cladding and insulation are correct, then there should have been many more horrific fires on this scale in England. Clearly there are reasons for this grateful outcome, which have not been investigated by the inquiry. Statistics in the UK are organized by component countries, so this article only considers the situation in England. (See for more articles: Grenfell Fire Articles Collection ).

Part 1: Calculating the number of high-rise buildings in England with ACM(LD-PE) cladding.

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According to the latest UK government statistics of September 2019, there are 435 high rise buildings (defined as over 18m+ or six storeys or more) in the UK with cladding that fail building  regulations (Building Safety Programme: Monthly Data Release Data as at 30 September 2019 and Table 5: descriptions of large-scale system tests undertaken by the BRE and the number of buildings with similar cladding systems – England, 30 September 2019  ). Just over a quarter have had remedial action on their cladding completed. In total 257 of these high rise buildings had or have ACM cladding of the worst kind that is rated as category 3.

This type of cladding has the potential to release over 35 MJ of heat for each kilogram of material. Aluminum plates do not burn, so the heat comes almost totally from the burning of the core material between the plates (there is also a small contribution from aluminum bonding and paint materials). Unmodified low density polyethylene (LD-PE) used on the Grenfell Tower rainscreen cladding, theoretically gives 45 MJ / kg when it burns. The rainscreen used has a 3mm LD-PE (unmodified low density polyethylene) core, which means 2.76 Kg of LD-PE per square metre (m2) of rainscreen, which gives potentially 124 MJ/m2. Given an 80% efficiency of combustion (the rest as smoke and unburnt volatiles) in a real fire scenario this means around 100 MJ/m2 is produced.

There is also the contribution of any insulation behind the rainscreen if it is combustible. The 100mm PIR (Polyisocyanurate) insulation layer used on Grenfell Tower had around half the heat release potential per square metre as the ACM(LD-PE) rainscreen cladding. This material forms a char layer (like wood) which slows or prevents combustion in real fire situations. The toxicity of this material is a huge problem, as it produces large amounts of toxic cyanide gas.

The fire spread risk therefore comes from the ACM(LD-PE) producing 100 MJ/m2 in minutes when exposed to fire. To put this in context the average UK home has an energy consumption of 150 MJ in electricity and gas in 24 hours. There are 257 high rise buildings in the UK with this type of ACM(LD-PE) cladding.

Part 2: Calculating the number of high-rise flats in England with ACM(LD-PE) cladding.

The report (Building Safety Programme: Monthly Data Release Data as at 30 September 2019) gives the number of self-contained dwellings (ie flats) for 339 of the 435 high rise buildings (defined as the usual 6 storeys or more, 18m+) being investigated (the other 86 buildings are student accommodation, hotels and a few government buildings). The average number of flats per high rise building being investigated is 84. There are 257 high rise buildings with ACM(LD-PE) rainscreen cladding under investigation, with therefore approximately 20,560 dwellings.

Part 3: Calculating the probability of a significant (fire service attended) fire in any high-rise flat in England.

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The number of fires sufficiently significant to be attended by fire services (FRSs) in high-rise flats (defined as over 18m+, or six storeys or more) for 2016 to 2017 is estimated as 1638. This was calculated as follows. The number of fires in purpose built flats of 10 storeys or more was 714. In purpose built flats of 4 to 9 storeys there were 1848 fires. Assuming that half these flats were between 6 and 9 storeys, the number would be 924.  Hence 1638 = 714 + 924. (See Fires in purpose-built flats, England, April 2009 to March 2017)

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There are approximately 408,000 high rise (defined as over 18m, or six storeys or more) dwellings (ie self contained flats) in England. This means in the period 2016 to 2017, 0.4% of high rise flats had fires attended by the fire services. Calculated as follows 1638 / 408000= 0.004 = 0.4%.

Part 4: Calculating the number of extensive serious fires in high-rise flats in England that have ACM(LD-PE) cladding.

In the period 2016-2017 there were approximately 82 significant (attended) fires in high-rise flats with ACM(LD-PE) rainscreen cladding. Calculated as follows 20560 * 0.004 = 82.2 .

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Of the 714 fires in all high-rise flats of 10 storeys or more in England in the period 2016-2017, 8% spread beyond the room of origin. So of the 82 fires in high rise flats (defined as the usual 6 storeys or more, 18m+) with ACM(LD-PE) cladding, there should have been about 7 which spread beyond the room of origin. Calculated as follows 82.2 * 0.08 = 6.58 .

It is not recorded how many of these fires broke through a window to interact with the cladding, so need to consider the reaction of modern double glazing to fire.

Part 5: The vulnerability of double glazing in flat fires.

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Modern double glazing is vulnerable to residential fires, according to many studies including this one from UL Firefighter Safety Research Institute (FSRI) from 2009 (see Analysis of Changing Residential Fire Dynamics and Its Implications on Firefighter Operational Timeframes).

A typical modern double glazed unit with a plastic frame and two panes (assembly E)  was mounted as part of the wall of a furnace (see UL Impact of Ventilation on Fire behavior in legacy and contemporary residential construction, by Stephen Kerber, 2008 updated 2010), where the internal (furnace) temperature then rose with the temperature curve below (red line):

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The standard cellulosic temperature curve (purple line) for building material testing is also shown for comparison to the UL9 and actual furnace temperature curves.

Over 3 tests the window construction “assembly E” failed at an average of 312 seconds (just over 5 minutes).

Part 6: Calculating the number of high-rise flats in England that projected fire for a sustained period onto ACM(LD-PE) cladding.

Clearly only a few fires, in high rise flats (defined as the usual 6 storeys or more) with ACM(LD-PE) cladding, spread from the room of origin to other rooms or communal areas. It is highly likely that these fires caused double glazing to break and were able to project fire to the external cladding for a sustained period of time.

So in 2016-2017 of the estimated 82 fires in high rise flats (defined as the usual 6 storeys or more, 18m+) with ACM(LD-PE) in England, about 7 would have spread beyond the room of origin, and have been able to project fire to the external combustible rainscreen cladding for a sustained period of time.

Part 7: Calculating total number of flat fires in England that projected fire for a sustained period on ACM(LD-PE) cladding.

Aluminum composite panels have been used in the UK since the mid 1990s, with a surge in use since the mid 2000s. Assuming the number of buildings with ACM(LD-PE) combustible cladding has expanded approximately linearly over the last 15 years; the number of high-rise flat fires in England since the mid 2000s that projected fire for a sustained period onto combustible external ACM(LD-PE) cladding, is estimated as 49 fires. Calculated as follows (15/2) * 6.58 = 49.35‬ .

None of these fires have gratefully created in England (or the UK generally) a horrific inferno on the scale of the terrible Grenfell Tower fire of 2017, which was the largest residential fire in England (and the UK) since the horrific bombing blitz of the Second World War.

Part 8: Recent well known residential tower block fires in England.

There was a terrible fire at the 12 storey tower block “Lakanhal House” in July 2009 in South London, that killed six people, and injured over twenty. There were multiple failures of fire safety in this 1950s block, after decades of botched fire-stopping work. It had been renovated in 2006-2007, where major fire safety problems had been ignored. The “high-pressure laminate window panels (HPL)” spread fire on the outside of the building, there was also a lack of cavity barriers in suspended ceiling voids, doors without fire-stopping and timber stairs.

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High pressure laminate (HPL) is essentially layers of paper impregnated with resins, and cured at high pressures. They have very little resistance to surface fire spread. This is the highly unsuitable type of material, that was used to make decorative formica kitchen table tops in the past.

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Many years before this there was a serious fire at the 11 storey “Knowsley Heights” tower block near Liverpool in April 1991. The tower block had been over-clad with “limited combustibility” fibre silica cement rainscreen sheets (by now defunct Cape Universal). The external concrete walls behind this rainscreen were painted with flammable rubberized paint. There was a 90mm deep cavity behind the rainscreen and no horizontal cavity barriers (fire breaks) were fitted.

Rubbish was set on fire in a re-entrant wall area, which then spread to the flammable paint, with the cavity behind the rainscreen acting as a chimney. The fire spread rapidly  to the top of the building, but mercifully no smoke or fire spread into the flats. Water applied by fire-fighters could not reach the fire raging behind the rainscreen.

A subsequent inquiry as a result of this fire and others eventually reported in 2000, and caused a change in building regulations in the UK (Approved Document B) in 2006, that mandated that there must be cavity barriers (fire breaks) in external cladding cavities, and that the external and internal surfaces of cladding must resist fire spread by being of limited combustibility (ie aluminum facings on foam insulation and aluminum plates around polymer cores in ACM rainscreen).

Neither of these notable fire incidents at Lakanhal or Knowsley Heights in England involved ACM(LD-PE) cladding.

Part 9: Recent well known residential tower block fires outside the UK that did involved ACM(LD-PE) cladding.

There have been major ACM(LD-PE) cladding fires in the Middle East, China and South Korea. In France the Mermoz Tower Block fire (2012) in Roubaix. In Australia the Lacrosse Tower Block fire (2014) in Melbourne. In the United States the 43 storey Borgata Water Club fire (2007) in Atlantic City. Many of these fires involved external curtain walling rather than overcladding. There are a lot of reports that make recommendations to avoid these types of high rise tower block fires. Mostly they focus on banning combustible cladding (ie ACM(LD-PE)  rainscreen) and combustible insulation, mandating sprinkler systems and fitting cavity barriers.

There is little widely accessible information on the use of cavity barriers at the time of these cladding fires, but the Australian Insurance Council in November 2017 noted:

“The [UK,2017] BRE Global tests provide our best indication to date as to the fire behaviour of the three most common categories of ACP’s [Aluminum Composite Panels, ie ACMs] installed on Australian buildings. One very important difference however is that cavity barriers were provided in all tests, whereas the provision of cavity barriers is not required in Australia and hence typically not specified.

Thus, the expectation is that the fire performance seen in the BRE Global results in the table, would probably be considerably worse with no cavity barriers installed. This is a significant concern for the Category 2 (FR or Fire Rated) ACP’s with any sort of combustible/fire retardant insulation or sarking installed behind the ACP.”

[ Source= https://www.insurancecouncil.com.au/assets/aluminium%20protocol/BRE_NOTES_ANEXURE.pdf ]

Also the manufacturer of the combustible ACM(LD-PE) rainscreen panels that were involved in the Mermoz Tower Block fire in Roubaix in 2012, made this statement:

“A spokesperson for 3A Composites, manufacturer of Alucobond, reiterates this: ‘The fire in Roubaix is subject to a legal inquiry. The official technical experts… have confirmed that the renovation of the façade, including the cladding material, was compliant [with] the building regulations in place.’

He stresses that Alucobond as siding material is one component of external wall construction and that other factors need to be taken into consideration with regard to fire safety: insulation material; sub-constructions, in particular with respect to the depth of the cavity; fire barriers to block the fire spreading in the cavity; installation complying with tests; cladding material; and sprinklers and fire escape routes.”

[ Source= https://www.insidehousing.co.uk/insight/insight/grenfell-the-french-connection-53571 ]

Rainscreen manufacturers have been grossly negligent in their supply and advertising of combustible rainscreen ACM products, given that they are aware of the fact that there have been serious fires fueled by these products, and they are banned for use on high-rise buildings in many markets. The statement by Alucobond is both self-serving and may also be factually correct.

Part 10: Conclusion, All high-rise ACM(LD-PE) fires in England need to be scrutinized.

The number of high-rise flat fires in England since mid the 2000s that projected fire for a sustained period onto combustible external ACM(LD-PE) cladding is estimated as 49 fires. The Grenfell Tower fire of 2017 was an horrific inferno that incinerated people in their own homes, and gratefully there have been no other residential fire disasters on this scale in England (and UK in general) since the Second World War.

If the Grenfell Inquiry is correct that the combustibility of the ACM(LD-PE) rainscreen (and to a lesser extent the PIR insulation) is the almost sole determiner of the extent of the Grenfell Tower fire (as separate from the scale of causalities) then there should have been many similarly horrendous fires involving ACM(LD-PE) cladding in England before Grenfell. There have not been.

Clearly the great majority of these particular smaller flat fires were not widely reported in the media as they did not spread. Some of these limited fires can be explained because they must have started on floors near the top of tower blocks, while others impinged on unclad sections of their exterior. The Grenfell Tower fire disastrously started near the base of a block completely clad in ACM(LD-PE) cladding. (It must also be noted that aerial fire fighting platforms can allow fire fighters to reach 25-30 metres up tower block exteriors (8 to 10 storeys), thus making active fire-stopping more effective on some high-rise fires if they are available).

The rest of the fires must have failed to spread due to some combination of active (ie fire fighters) and passive (ie cavity barriers) fire-stopping measures. Given that the high-rise tower blocks with ACM(LD-PE) cladding have been identified, then there must be related fire service records and cladding repair records, that can be scrutinized to determine  the nature of the spread of tower block ACM(LD-PE) fires. The Grenfell Inquiry has relied on (often media) reports of notorious fires in tower blocks with ACM(LD-PE) panels in curtain walling rather than rainscreen systems, with much wider cavities, and constructed to different building regulations and product standards, in other regions of the world.

The issue of getting information about cladding fires in tower blocks, came up during the UK Parliament Inquiry in 1999-2000 on the “Potential Risk Of Fire Spread In Buildings via External Cladding Systems”. A memorandum from the then Department of the Environment stated, “2.2  The Department has a call-off contract with the Fire Research Station [UK BRE] to investigate real fires and this highlights any areas of concern that affect Building Regulations.” A similar memorandum from the Fire Brigades Union stated “2.4 Fires involving fire spread via external cladding have occurred before however, in the short time available to create this response it has been impossible to obtain comprehensive details of dates, times and places. No doubt the Home Office—Fire and Emergency Planning Directorate (FEPD) and the Department of the Environment, Transport and the Regions—Building Regulations Division (BRD) will have the details.” No one was monitoring the potential risk of cladding fires in tower blocks, or the factors that limited these fires. Instead there was only investigative action after a serious event.

The Grenfell Inquiry needs to compile the data on all ACM(LD-PE) cladding fires of any size in tower blocks in England, to determine the actual rather than extrapolated behaviour of this type of fire. All the causes of the horrific Grenfell Tower fire need to be established. All the companies and organizations that failed the victims need to be identified.

 

 

 

Problems With Professor Torero’s Expert Report and Witness Statements On Grenfell Tower Fire.

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Problems With Professor Torero’s Expert Report and Witness Statements On Grenfell Tower Fire.

[ Posted by Lara Keller 16/10/19 ] anchorTableSmall - Copy Blog Table Of Contents

Continuing articles on the terrible Grenfell Tower Fire of 14th June 2017 in London. This one focuses on the Professor Torero’s Expert Report And Witness Statements, presented to the Grenfell Inquiry in 2018, looking at the causes of the rapid fire spread in Grenfell Tower. Originally presented as a tweet thread. (See for more articles: Grenfell Fire Articles Collection ).

Part 1:

1. In 2018 Professor Torero expert report (updated Oct 2018), stated that professionally installed cavity barriers would not have stopped flame spread on Grenfell Tower, but more test data was needed on their effect on the speed of flame spread.

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Part 1.1:

1.1 Professor Terero’s report states aluminum plates in the rainscreen would offer “no protection” to the combustible cladding materials, because typical flame temperatures are above the melting temperature of aluminum (650 C). Assume he means by typical the constant flame region (approx 900 C and above depending on fire type), while the flame tips are by convention 550 C. His statement about melting temperatures is true if metal is engulfed in flame, but not necessarily true if the aluminum is exposed to flame on one surface only (additionally separated by small flame “stand off” distance).

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Part 2:

2. Prof Terero’s witness testimony to the Grenfell Inquiry stated that cavity barriers had “no meaning” but could be “potentially slowing” the flame spread. He does not appear to know which?

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Part 3:

3. In Professor Terero’s witness testimony to the Grenfell Inquiry on gaps left in the horizontal cavity barrier line (installed in upside-down), he compares gaps to the size of cavity, not the narrow gap between intumescent strip and the back of the rainscreen. He then states that cavity barriers errors have “no significant” effect.

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Part 3.1:

3.1 The size of the gaps in the horizontal cavity barrier line on the columns appears to be EQUAL to the PROTECTED gaps (even before considering botched undersized cutting of cavity barriers). In his witness statement to the Grenfell Inquiry Professor Torero considered cavity barriers in the horizontal spandrels rather than the columns. The columns were where the fire spread was rapid and contributed most to a flat fire becoming a fire involving a whole tower block. 

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Part 4:

4. Despite Profesor Terero’s expert report and witness statements to the Grenfell Inquiry with their contradictory statements on cavity barriers (or VRBs=ventilated rainscreen barriers), when asked is further tests needed to understand Grenfell flame spread and VRBs he said no. He said it would all be too complicated.

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Part 4.1:

Part 4.1: The rainscreen system at Grenfell Tower was unprofessionally designed and implemented. Profesor Terero puts the blame solely on the combustible type of materials chosen. It would not be complicated to test the rainscreen installation – with the materials chosen – that was used on Grenfell Tower, while installing them professionally. This would show the relative effect of the materials versus the installation. There is no need to replicate the complicated botched installation as Professor Torero states.

Part 5:

5. Dr Babara Lane stated that Professor Torero is responsible for the fine detail of “fire and smoke” behavior. Clearly his testimony is vitally important to the credibility of the Grenfell Inquiry.

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Conclusion.

Professor Torero’s report and statements are difficult to make sense of. He presents the common sense case that the rapid cladding fire that engulfed the Grenfell Tower was caused overwhelmingly by the combustible nature of the cladding materials. He consistently understates the botched nature of the passive fire-stopping (especially cavity barriers in the rainscreen cavity). This may be the correct judgement and distortions are a result of the pressure to present clarity.  This may be the result of the relative power of the UK construction industry as compared to foreign manufacturers of the cladding materials (+UK Fire Fighters), with the need to stop this terrible fire from overturning decades of lobbying for deregulation. There may be another reason. The only way to resolve this is further testing specific to this fire, which Professor Torero states is too complicated. The victims of the fire deserve the full truth.

 

 

 

Reason 1 – Cavity Barriers Too Slow – Dr Barbara Lane 1st reason for the failure of horizontal cavity barriers on Column B5 Pathway A of Grenfell Tower.

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Reason 1 – Cavity Barriers Too Slow – Dr Barbara Lane 1st reason for the failure of horizontal cavity barriers on Column B5 Pathway A of Grenfell Tower.

[ Posted by Lara Keller 16/10/19 ] anchorTableSmall - Copy Blog Table Of Contents

Continuing articles on the terrible Grenfell Tower Fire of 14th June 2017 in London. This one focuses on the evidence about the alleged slowness of cavity barrier activation in the rainscreen cavity, presented to the Grenfell Inquiry in 2018 by Dr Barbara Lane, looking at the causes of the rapid fire spread in Column B5 (Pathway A, Reason 3). The rapid fire spread in this column changed the fire from a restricted external fire centered on Flat 16’s kitchen window, to a fire that involved the whole height of the tower block. Originally presented as a tweet thread. (See for more articles: Grenfell Fire Articles Collection ).

Part 1:

1. Section 10 Dr Barbara Lane’s 2018 Expert Report to the Grenfell Inquiry
stated that the initial route of widespread cladding fire spread was vertically up column B5. The “externally visible” fire spread was 19 floors in 12 minutes. This article is an examination of the 1st reason she presents, on the slowness of activation of the cavity barriers.

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Part 2:

2. According to a witness statement by Fire Fighter (FF) Desmond Murphy referenced by Dr Lane, the fire was burning for some time in the cavity behind the rainscreen, before it suddenly changed mode, moving up the building behind the rainscreen, like “neon” lighting switching on, 5 floors in 15 seconds.

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Part 3:

3. Dr Lane’s report, Section 10, gives reasons why horizontal cavity barriers failed in the critical initial major fire pathway up the cladded B5 column (see Pathway A). These reasons appear non specific, and do not hold up to close examination.

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Part 3.1:

3.1. 2013 Tests on the Siderise RH 25 (120/60) 25mm air gap cavity barriers used on Grenfell Tower, showed the barriers created an effective seal within 60 seconds using the standard “Cellulosic Temperature Curve”. Temps above barrier only briefly exceeded 180C. This is illustrated below:

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Part 3.2:

3.2 Also in 2018 ABI (UK Insurance Organization) commissioned tests on ventilated cavity barriers. A steeper temperature curve was used, which resulted in faster effective cavity seal in 20-33 seconds for mineral wool intumescent type Cavity Barriers (ie like the Siderise RH 25 type).

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Part 4:

4. Short exposure to fire above horizontal cavity fire barriers before they close is highly unlikely to lead to self sustaining fire. Two Single Burning Item SBI (EN13823) tests had a burner deliver 2 x 18=36 MJ over 10 minutes to samples of the insulation and rainscreen used at Grenfell Tower, which induced only 5.26+2.2= 7.46 MJ heat  output from fire.

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Conclusion.

It is highly unlikely that fire spread behind the rainscreen past the cavity barrier, during the 30 seconds before a correctly installed cavity barrier would activate and seal the gap.

 

 

 

Reason 2 – Rainscreen Core Melts – Dr Barbara Lane 2nd reason for the failure of horizontal cavity barriers on Column B5 Pathway A of Grenfell Tower.

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Reason 2 – Rainscreen Core Melts – Dr Barbara Lane 2nd reason for the failure of horizontal cavity barriers on Column B5 Pathway A of Grenfell Tower.

[ Posted by Lara Keller 15/10/19 ] anchorTableSmall - Copy Blog Table Of Contents

Continuing articles on the terrible Grenfell Tower Fire of 14th June 2017 in London. This one focuses on the evidence about the polyethylene core of the rainscreen panels melting so providing a route for fire to bypass cavity barriers, presented to the Grenfell Inquiry in 2018 by Dr Barbara Lane, looking at the causes of the rapid fire spread in Column B5 (Pathway A, Reason 3). The rapid fire spread in this column changed the fire from a restricted external fire centered on Flat 16’s kitchen window, to a fire that involved the whole height of the tower block. Originally presented as a tweet thread. (See for more articles: Grenfell Fire Articles Collection ).

Part 1:

1. Dr Lane’s report, Section 10, gives reasons why horizontal cavity barriers failed in the critical initial major fire pathway up the cladded B5 column (see Pathway A). This article is an examination of the 2nd reason.

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Part 2:

2. There is less information about Low Density Polyethylene (LDPE) at the temperatures it’s viscosity has sufficiently reduced, due to thermal decomposition, for it to flow Most research is on manufacturing. Conservative estimate of 320 C obtained.

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Part 3:

3. Imagine a UK standard BS8414 test rig, with a 4mm thick ACM sheet as the test cladding. There is no backing wall, and the temperature behind the cladding is adjustable. Which part of the ACM sheet will have Unmodified (Low Density) polyethylene that melts and flows away?

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Part 4:

4. Calculations of heat fluxes, shows at 5m the fire plume is at 440 C (just above flame height of 4.5m), the ACM LDPE is at 320 C, with 200 C behind the ACM. In this situation the LDPE would melt and flow away.

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Part 5.

5. Estimate of the tensile strength of the 3105-H25 Aluminum Alloy used in Reynobond ACM cladding is 29 MPa (N/mm2) at 320 C (18% of room temperature value). The aluminum sheets would still keep their integrity.

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Part 6:

6. Therefore if LDPE core of the cladding melted and flowed away from between intact aluminum sheets, the cladding (near the cavity barrier) would have to be just above the external flame height. The evidence is that fire in cavity on the columns preceded external fire over many floors, making this route redundant.

Conclusion.

It is likely that fire spread between the aluminum plates of the rainscreen was insignificant.

 

Reason 3 – Panel Distortion – Dr Barbara Lane 3rd reason for the failure of horizontal cavity barriers on Column B5 Pathway A of Grenfell Tower.

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Reason 3 – Panel Distortion – Dr Barbara Lane 3rd reason for the failure of horizontal cavity barriers on Column B5 Pathway A of Grenfell Tower.

[ Posted by Lara Keller 11/10/19 Updated 12/10/19 ] anchorTableSmall - Copy Blog Table Of Contents

Continuing articles on the terrible Grenfell Tower Fire of 14th June 2017 in London. This one focuses on the evidence about panel distortion and cavity barriers, presented to the Grenfell Inquiry in 2018 by Dr Barbara Lane, looking at the causes of the rapid fire spread in Column B5 (Pathway A, Reason 3). The rapid fire spread in this column changed the fire from a restricted external fire centered on Flat 16’s kitchen window, to a fire that involved the whole height of the tower block. Originally presented as a tweet thread. (See for more articles: Grenfell Fire Articles Collection ).

Part 1:

1. Dr Lane’s report, Section 10, gives reasons why horizontal cavity barriers failed in the critical initial major fire pathway up the cladded B5 column (see Pathway A). This article is an examination of the 3rd reason.

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Part 2:

2. Dr Lane uses the example of ACM panel distortion for “wing” panels 2A and 1A (approx 5% versus length) from the BRE(UK) DCLG5 Test of August 2017 . The wooden crib fire burned for the full 30 minutes in this test. It involved testing PIR insulation and ACM panels (with limited combustibility mineral filler core), which were the least fire reactive materials used in the tests. Measurements calculated taken from the report’s photograph are based on comparison to components of the rig of known size.

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Part 3:

3. The temperature profile of the exposure of the middle of the bottom of panel 2A is estimated using the readings of the slightly lower external thermocouple (tc: 1007) at the middle of the “wing” of the DCLG5 BS8414 test rig at the top of panel 1A.

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Part 4:

4. The external fire plume temperature of 450 C is used (with an averaging method that works for the fire plume wall temperature on the “main face”). The cavity temperature is taken as 200 C, based on thermocouple readings at the top of the panel, and the assumption that air movement is downward on the cooler and upwards on the hotter side of the panel. The temperature profile of the middle of the bottom of panel 2A ranges from 329 C on the outside to 303 C on the inside, with the centre of the panel core at 316 C.

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Part 5.

5. Using the idea that the curvature of the distortion is constant the expansion of the distorted panel can be estimated as 3.5mm over a 296 C temperature rise (25mm distortion over 475mm panel width). This expansion closely matches the coefficient of linear thermal expansion of Aluminum Alloy (3105) applied to the width and temperature change of this ACM panel. The expansion of a core material whether mineral or polyethylene is much greater.

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Part 6:

6. So ACM panels distort following thermal expansion of their outer Aluminum Sheets, while lateral expansion of their more expansive cores are contained by bonding to these sheets (the width of the cores increase instead). To pass BS8414 tests cavity barrier Intumescent strips must be also able to expand slowly further (after initial rapid activation expansion to seal the cavity) to allow for distortion of correctly supported panels.

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Part 7.

7. It can be estimated that the intumescent strip of Siderise RH25 90/30 if exposed to a fire plume at 450C, would expand in volume at least 25 times. There  is a lack of  available technical information on Siderise products (apart from test reports), so used information on similar Tenmat FF102/25 product.

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7a. Tenmat FF102/25 expands 26 times at 400 C according to the product datasheet.

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Part 8.

8. The actual intumescent strip in the bottom half of panel 2A in DCLG5 test, would need to expand approximately 8.5 times to seal the undistorted panel.

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8a. The actual intumescent strip in the bottom half of panel 2A in DCLG5 test, would need to eventually expand approximately 17.5 times to seal the distorted panel. (by exposure to 450 C Fire Plume). Clearly these intumescent strips are capable of doing this in terms of expansion ratio (Maximum 25 Times).

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Part 9.

9. Dr Lane seems to suggest that intumescent strips do not respond successfully to panel expansion.

Part 10.

10. Lastly in DCLG Test 5, failure of support structures corresponds to areas where panels were burnt away. Panels reduce temperatures in cavities, and any support structure is installed to account for some thermal expansion. Damage to panels appears to precede damage to support structure that they protect.

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Conclusion.

Cavity barriers can expand to respond to panel distortion within given limits. Panels fail before support structures.

 

Reason 4 – Botched Installation – Dr Barbara Lane 4th reason for the failure of horizontal cavity barriers on Column B5 Pathway A of Grenfell Tower.

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Reason 4 – Botched Installation – Dr Barbara Lane 4th reason for the failure of horizontal cavity barriers on Column B5 Pathway A of Grenfell Tower.

[ Posted by Lara Keller 10/10/19 Updated 12/10/19] anchorTableSmall - Copy Blog Table Of Contents

Continuing articles on the terrible Grenfell Tower Fire of 14th June 2017 in London. This one focuses on the evidence of botched installation of cavity barriers, presented to the Grenfell Inquiry in 2018 by Dr Barbara Lane, looking at the causes of the rapid fire spread, in Column B5 (Pathway A, Reason 4). The rapid fire spread in this column changed the fire from a restricted external fire centered on Flat 16’s kitchen window, to a fire that involved the whole height of the tower block. Originally presented as a tweet thread. (See for more articles: Grenfell Fire Articles Collection ).

Part 1:

Dr Barbara Lane presents 3 reasons for failure of horizontal cavity barriers on column B5 Pathway A (the others apply to horizontal spread). She then gets on to the key 4th reason about the actual installation (planning, design and application) of the cavity barriers. This is the most substantial. The summary presented in Section 10.3.40 of her report (section 10) neglects some of her own and others significant evidence.

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Part 2:

The gaps in the line of horizontal barriers around the non-corner (“face”) columns were grossly inadequately protected by cavity barriers. At least 270 cm2 were unprotected, while 250 cm2 were protected by cavity barriers.Vertical cavity barrier is not shown. This was on the face of the column furthest from the source (the kitchen window of Flat 16), and had little effect on the vertical spread of the fire up column B5).

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Part 3:

The vertical channels in the external surface of the original concrete columns were unprotected, so creating voids for vertical fire propagation.

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Part 4:

The vertical cladding rails on the edges of the face columns were continuous, creating extensive unprotected vertical voids. The position of the panels and the flange on the panels almost closed the gap between this void and the external air.

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Part 5:

The vertical cladding rails on the edges of the face columns created an unprotected vertical void, which was connected to the rainscreen void by a 257cm x 2cm (approx 510 cm2) air gap.

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Part 6:

The vertical cladding rail on the apex of the face columns were continuous, creating extensive unprotected vertical voids, inside the rail and either side of the rail. The position of the panels and flange on the panels almost closed the gap between this void and the external air.

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Part 7:

The vertical cladding rail on the apex of the columns created an unprotected vertical void, which was connected to the rainscreen void by a 2 x 257cm x 2cm air gap.

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Part 8:

Systematically Negligent Workmanship. Large area of unprotected voids throughout the horizontal cavity barrier line were left unprotected. In the case below the horizontal cavity barrier has been crushed to fit with a projecting part of the vertical cavity barrier, creating another unprotected void.

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Part 9:

Systematically Negligent Workmanship and Design. Unnecessarily odd shaped poorly supported length of horizontal column cavity barrier cut to fit continuous cladding rail and spandrel cavity barrier. Rail should have gaps for column horizontal barrier. The lengths of cavity barrier should be joined between column and spandrel barrier by symmetric mitre joints.

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Part 10:

Systematically Negligent Design And Workmanship. Undersized column cavity barrier, that created a gap (to the inner surface of the rainscreen panel) over 25mm for 75% of the cavity barrier width (gap rises to 55mm near apex). Appears barrier cut to fit incorrectly designed continuous cladding rail.

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Part 11:

Systematically Negligent Workmanship. Odd shaped length of horizontal cavity barrier, only supported by one bracket. Appears to be hacked into shape. Siderise (and other CB manufacturers’) Installation Guides consistently stress reducing and sealing any remaining gaps is essential.

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Conclusion

There was no effective cavity barrier installed in the face column B5 of Grenfell  Tower, and probably in none of the other face or corner columns.

Strong PR attempt to mislead the UK public about the causes of the Grenfell Tower Fire.

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Strong PR attempt to mislead the UK public about the causes of the Grenfell Tower Fire.

[ Posted by Lara Keller 12/12/17 Updated 18/6/19 ] anchorTableSmall - Copy Blog Table Of Contents

Have not written about the terrible Grenfell Fire since early August 2017, as I spent a month before that, looking at everything I could about the fire engineering causes behind the “rapid fire spread” in the cladding (See Grenfell Everything I Have Learned On The Causes Behind The Inferno ).

The media today reported that the Police are investigating contractors for criminal negligence. Concerned that since the fire in June there has been a strong PR attempt to mislead the UK public about the causes of the fire. In the media the blame has been pinned on the flammability of the rainscreen and insulation (that make up the cladding system). This was reinforced in July by government agency BRE testing of the cladding materials in a perfectly installed setup, in a so called “full scale” BS 8414-1 test. This test showed the materials did not meet the fire compartmentation regulations.

The impression has been given that the “rapid fire spread” in the cladding during the Grenfell Tower Fire was entirely due to the cladding materials used. There is an important element that has been ignored in the media. This is cavity fire breaks, or more technically ventilated cavity fire barriers.

The previous article from August (See Grenfell Everything I Have Learned On The Causes Behind The Inferno ) describes in detail that none of the tests on the cladding materials explains the “rapid spread of the fire”. They do explain how a serious fire would have occurred, that would have spread to some adjoining flats, but do not explain how the whole 22 floor tower block was engulfed in flames in around 20 minutes.

This rapid fire spread requires a wind tunnel effect in the cavity behind the rainscreen and the insulation. This requires that a large percentage of the air gaps in the cladding cavity at the floor levels, were not blocked by correctly installed cavity fire barriers. This involves botched installation, botched cladding design and manufacture, and botched inspection. There is a strong case for an investigation into negligence for profit, that lead to the horrific deaths and injuries at Grenfell Tower.

Some discussion has appeared in the construction industry press about cavity fire barriers and Grenfell. Selected building experts have been suggesting fire barriers are difficult to install, and may not work in all situations. The apparent intention is to undermine the importance of cavity barriers.

There was a useful article in September 2017 “Inside Housing” Grenfell: what did the cladding tests show?  It includes this paragraph:

“To provide proper insulation, installers leave a cavity between the panels [rainscreen] and the foam [insulation], and it is in this void that fire safety issues can arise. In order to preserve the cavity but also prevent it from becoming a deadly chimney, fire breaks are generally installed at regular intervals. These do not block the cavity entirely, but are designed to expand when they detect fire and fill the gap [damp insulation is less effective].

Arnold Tarling, a fire safety expert and chartered surveyor at Hindwoods, has little faith in this idea. ‘How,’ he questions, ‘do you make sure that this continues across every vertical member which is holding the cladding on? The external cladding’s got to stick to something, and so very often you have vertical sections of aluminium bonded to the concrete. You have your barriers coming out from there. How do you fill in all those cavity bits and pieces – the aluminium tubes themselves? How do you fill in the cavity gaps? It becomes very complicated.’ ”

This gets to the heart of the Grenfell rapid fire spread. The design, construction and installation of the cladding was done of the cheap. Looking at limited information on the cladding installation it is highly possible that over 50% of the cavity gaps where the Grenfell Tower columns intersected with floor levels was left completely unprotected (See Grenfell Everything I Have Learned On The Causes Behind The Inferno ).

It is necessary that there is a fight red in tooth and claw to ensure justice for the victims of this fire. Then secondly comes ensuring it does not happen again, and that the UK construction industry is properly regulated (currently building regulations are becoming a joke, which impacts on wider government regulatory climate). Finding suitably qualified fire safety experts to go against the ire of the powerful UK Construction Industry Lobby and its resources will be a major problem.

Grenfell Everything I Have Learned On The Causes Behind The Inferno.

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Grenfell Everything I Have Learned On The Causes Behind The Inferno.

[ Posted by Lara Keller 5/8/17 Updated 7/7/19 ] anchorTableSmall - Copy Blog Table Of Contents

1. Introduction: Grenfell Tower Fire

Grenfell Tower fire in the early hours of the 14 June 2017, spread with incredible speed spreading from the 4th to the top 24th floor in 20 minutes. Over 80 men, women and children has been killed by toxic fumes and heat, and their remains cremated. It really is not too strong to describe this as the most horrific fire in the UK since the Second World War. To keep any respect for democracy and government regulation in the UK, the residents of Grenfell Tower need to get full justice, and there needs to be urgent action to make residential housing (social, student or private) safe in the UK. On a more personal level I was shocked by the death of Mohammed al-Haj Ali a young civil engineer who had been forced to flee the malevolent state of Assad’s Syria, only to become a victim of the indifferent UK state. It is a bitter irony that indifference for life does not respect borders.

The thing that marks this Tower Block fire out from previous ones is the very rapid speed of the fire spread, and the high number of deaths and injuries. The main issue in getting justice is understanding the “rapid fire spread”. In this article I ignore the cause of the kitchen flat fire and sprinklers. I ignore even the response of the fire services, fire stopping around windows, fire doors, and the quality of the escape routes and fire advice (“Stay Put Policy”). The reason is that the authorities will argue if Grenfell had been a normal fire these systems would have worked. I will also ignore the disgraceful treatment of the residents before and after the fire by the super wealthy penny pinching social cleansing Kensington and Chelsea Council. This is an important issue, but who is actually directly responsible for the crime of refurbishing Grenfell Tower to make it a death trap needs to be established, and this means looking deeply at the cause.

In the weeks following the fire, there were several fire engineering experts giving concrete informed opinions on the fire in the UK media. This from the Daily Telegraph http://www.telegraph.co.uk/news/2017/06/24/grenfells-unusual-design-led-blaze-spread-say-investigators/   it quotes a “well places source” putting focus on voids in the cavity behind the rainscreen (termed “cladding” by media) on the Tower Blocks columns (some architects term these “fins”).

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Early video of the fire appeared on BBC Newsnight, showing the two columns near the 4th floor (close to the North-East corner) flat where the flat started, on fire from the 4th to the 24th floor, the entire height of the building is in flames in 20 minutes.

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2. Cladding and ventilated cavity barriers.

So it seemed from several sources that fire stopping in the cladding cavity on the columns was the key area to look at. The media at this time were still just reporting that the Reynobond PE rainscreen used, had a flammable Polyethylene core, and this was the nearly the sole cause of the rapid fire spread. Obviously the Polyethylene is a major cause of the fire, but is it like the “bullet” with the botched fire stopping in the cladding as the “gun”.

Cladding is fitted on to a 1970s Tower Block like Grenell Tower, to bring the insulation up to modern standards, stop the degrading of the concrete walls by weather, stop damp getting into flats and to improve the outside appearance. It is fitted as a “cladding” system like this:

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The word Cladding is often used to refer to all the layers, with the outer one being called Rainscreen. There was a standard 50mm cavity gap between the Rainscreen and the Insulation at Grenfell. This allows the insulation to stay dry, as it is only effective if dry. This ventilated cavity is essential so that changes in air pressure between the inside and outside of the building will not draw rain into the cavity. The problem with this, is that fire can get into the cavity gap and spread unseen between floors.

To stop this and to still allow ventilation, at each floor level a complete line of Ventilated Cavity Fire Barriers is installed, which goes from the layer of the Concrete Wall to the Rainscreen. Steel brackets hold them firmly in place. A 25mm air gap is left between the Cavity Barrier and the Rainscreen. The Cavity Barrier contains a layer treated with an Intumescent material, that expands when exposed to heat. So when the cavity reaches typically 180 C, the line of Cavity fire Barriers should have fully expanded to close the 25mm air gap left in the cavity. Each floor level section of cavity in the cladding is then sealed from the floor above and below.

There are lots of companies who make Ventilated Cavity Fire Barriers, and I do not know who makes the best ones. Here is an informative piece from a company called Tenmat  http://www.tenmat.com/passive-fire-protection/ventilated-fire-barriers :

grenfellCavityBarriersTenmat

I do not have had connection to people who make any of these cladding products, my only concern is that Grenfell Residents get full justice, which means looking into the construction details and so trying to get at the root cause of the rapid fire spread.

3. The Chimney Effect.

The Chimney Effect refers to how vertical cavities without fire barriers, can act like chimneys, which can create very powerful upward drafts. Obviously this updraft extends flames upwards, and carries molten droplets of plastics used in Rainscreen (like Polyethylene) upwards. This updraft also effects how semi combustible “charring” cladding products like PIR insulation burn. Here is a graph showing the “chimney effect”. It’s force is driven by the height of the chimney and the temperature of the fire at the bottom of it. The updrafts are then compared to the pressure you would feel from outside wind speeds on the Beaufort scale. At Grenfell the distance from the 4th floor flat to the top flat is around 45m.

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[Important Note: The cladding added to tower blocks is ventilated along its entire height. Therefore this is a “leaky” chimney effect. The updraught figures above are the upper boundary of what is possible and refer to a non-leaky chimney. ]

To know how semi combustible products used on Grenfell Tower would react to a “chimney effect” in a 45m cavity, requires looking at the fire behavior of these materials.

4. Tests of the individual cladding materials used.

At end of June 2017 the BRE (UK Building Research Establishment) were testing small samples of materials cut from Grenfell and other Tower Blocks. The Guardian newspaper reported that these tests were less than transparent and not to standard procedures: https://www.theguardian.com/uk-news/2017/jun/26/tower-block-cladding-tests-after-grenfell-fire-lack-transparency-say-experts . It was being reported that the samples of rainscreen and insulation from Grenfell both failed these fire tests: [Det Supt] McCormack said: “Preliminary tests show the insulation samples collected from Grenfell Tower combusted soon after the tests started. The initial test on the cladding tiles also failed the safety tests.” (https://www.theguardian.com/uk-news/2017/jun/23/grenfell-tower-fire-police-considering-manslaughter-charges).

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I looked at previous fire tests for the the Rainscreen (Reynbond 55 PE, 0.5mmALU-3mmPE-0.5mmALU) and the Insulation (Celotex rs5100, which is 100mm depth version of rs5000). According to various brochures for these materials they are fire rated in the UK as Class 0. This translates to Euroclass B as the table below shows:

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Euroclass ratings use the Single Burning Item (SBI) Test, which uses a 30KW Propane Burner to heat a sample of the material in a special high tech room where the heat produced and combustion products  are analyzed, to determine how much energy the sample has released and what gases, smoke and droplets are formed. (http://www.sp.se/en/index/services/firetest_building/firetest_bu%C3%ADlding/EN_13823_SBI/Sidor/default.aspx). Two sheets of the material (1m x 1.5m and 0.49m x 1.5m) are mounted on a trolley in a corner configuration. The burner is mounted at the base of the corner, and heats the material for 21 minutes.

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[Important Note: Since this was orginally written Celotex rs5100 has been withdrawn. It has reclassified from UK specification Class 0 to a Class 1 material. A test by Exova Warringtonfire WF 383671 on 17/8/17. The THR(600) ie 10 minute heat release in the SBI Test for the rs5100 (100mm) PIR product was 5.26 MJ. The change in classification may be due to the Fire Growth Rate (FIGRA) which measures the peak heat release. Still uncertain at this time. 7/7/19]

Celotex rs5100 is rated as Euroclass B, which means the heat energy produced by the burning sample in 10 minutes is less than or equal to 7.5 MJ  (THR600s <= 7.5 MJ). The 30KW propane burner supplies 18 MJ to the sample over 10 minutes, and the sample produces 7.5 MJ or less. Do not have the exact THR600s for rs5100, only that <= 7.5MJ. The sample is 2.24 m2 of rs5100. Rs5100 weighs 3.38 kg/m2 and PIR produces approximately 26 MJ/Kg when burnt. So the sample could produce 197 MJ if completely burnt. Therefore less than 4% of the heat energy contained in the insulation is released in this test.

This PIR type foam, is a modified rigid thermoset type of polyurethane, that consists of rings of molecules strongly cross linked, as opposed to thermoplastics formed of loosely bound chains of molecules.  When heated with a blow torch PIR burns, forming a char layer, but goes out when the torch is removed. There is also an adhesive layer of relatively thick aluminum foil attached to the PIR to resist ignition.

There is a test for the Reynobond 55 PE panels (0.5mmALU-3mmPE-0.5mmALU) (CSTB Report No. RA11-0032 9/2/2011) that gives THR600s as 2.2 MJ.  These panels consist of two sheets of 0.5 mm Aluminum (the 55 refers to this) bonded to a 3mm largely unmodified polyethylene core. Basically the Aluminum prevents very much of the core being exposed to oxygen, where heat can be applied to it to make it burn. So is you supply 18 MJ of heat with a propane burner to a sample of  Reynobond 55 PE panels, you will only generate 2.2MJ of heat from areas of the panels that have been burning. This fire is therefore not self sustaining.

The sample is 2.24 m2 of Reynobond 55 PE. The 3mm polyethylene core provides 0.003  m3 per m2 of panel. Polyethylene weighs 950Kg/m3. So each m2 of panel provides 2.85 Kg of polyethylene. Polyethylene produces approximately 43 MJ/Kg when burnt. So the sample could produce 275 MJ if completely burnt. Therefore less than 1% of the heat energy contained in the rainscreen is released in this test.

It is difficult to know what tests and standards the BRE (UK Building Research Establishment) were using when they did their single item burning tests on samples of rainscreen and insulation. The London Metropolitan Police did say in a press conference the Rainscreen was harder to burn than the Insulation. The media reporting about the Rainscreen had given the impression that if a corner of it was lite with a burner the whole cladded building facade would go up in flames. The reporting of these first small scale  BRE tests was very limited , and tended to reinforce this impression that “cladding materials only” was the reason for the rapid fire spread.

5. Overview of “natural” wall and chimney fires.

When a solid item burns, fuel vapour is released from the item as it heats up. A buoyant plume is formed, which in natural fires of sufficient size is turbulent (has eddies) and contains unburnt fuel vapour. The energy from the burning vapour produces heat radiation (infrared waves) and heats the air pulled into the plume as it rises (“entrainment”).

The heat supplied (whose density over an area is called “heat flux”) to an inert wall from a fire at its base, can be due to radiation or convection (direct transfer from hot gases). The density of the heat flux and the proportion of radiation to convection changes with height and how much soot is in the plume (sooty flames produce move infrared radiation). The lower part of the plume that contains flames corresponds to the section that contains unburnt fuel vapour. Above the flame height the plume spreads out and dilutes its energy.

If the fire is below an inert chimney, the infrared radiation produced by the flames must all be directed towards the walls of the chimney, and the hot gases of the fire are squeezed into a smaller faster moving cross section so increasing convection to the walls. Updraft pulls more oxygen into the fire, and increases the rate of burning and the speed of plume. When compared to wall fires the plume will supply more heat energy to the walls of the chimney, and the flame height will be much greater.

If the walls of the chimney are not inert, then a growing positive loop develops as the burning walls of the chimney create more updraft. This is why stopping the chimney effect in the gap between the rainscreen and insulation is absolutely critical with cladding materials which are in in any degree combustible.

5. How “chimney effect” would have effected Grenfell cladding materials.

Taking the case of the PIR Insulation Celotext rs5000 used at Grenfell. A vertical wall of this material is going to burn more fiercely if trapped in a cavity behind rainscreen. Much more of the heat energy from an area of burning insulation is going to directed back to the area of insulation above it, rather than being lost to the open air. As PIR insulation burns it forms a solid char layer. Rather than the hot plastic foam breaking up into a gas that more easily mixes with air. A strong updraft forces oxygen into the char layer and so helps it burn. The same idea applies to the uses of the bellows in a blacksmith’s charcoal forge.

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So in the scenario above a section of vertical semi-combustible cladding (rainscreen, cavity, insulation) is subject to an intense fire in an iron crib at the bottom:

On the Left the rainscreen near the crib fire burns, and cannot enter the cavity because cavity fire barriers have closed it. The insulation nearest the crib fire burns most intensely, but much of the resulting heat energy is lost to the open air. The sections of insulation above this burn less intensely as the amount of supplied heat diminishes. This is more like the fire behavior of PIR insulation in a room corner “single item burning” test.

On the Right there is the same set up, but with no (effective) cavity fire barriers. Fire from the crib enters the cavity and is drawn up like a chimney. A strong updraft and the more efficient movement of heat energy up the surface of the burning insulation means the whole surface can burn more fiercely and rapidly. This is very different fire behavior than the room corner “single burning item” test. It also means that it needs a smaller total quantity of combustible material to create a serious fire within a cavity. It has been reported that in the rainscreen and the insulation, when added together, there was the calorific equivalent of 15 tonnes of combustible material on the outside of Grenfell Tower.

Also the Rainscreen would burn differently in the two scenarios above:

On the Left the Rainscreen will only burn to a certain height and then stop. The single item burning tests show it needs external supplied heat to burn, and this falls rapidly with distance from the crib fire. The intensity of the Insulation burning is falling off with height, as heat is lost, and so cannot supply heat to the Rainscreen.

On the Right the Rainscreen burns due to the crib fire in the same way, but the fire moves up the cavity like a chimney. The insulation burns fiercely, and the trapped heat also heats the Rainscreen. The polyethylene core softens and the bond with the outer aluminum sheets weakens. This means when the liquid polyethylene is drawn into the cavity and ignites it will burn much more fiercely, than in the corner of the room “single item burning” test.

It seems highly probable that the sudden bursting into flames of sections of Reynobond PE Rainscreen on the columns at the Grenfell Tower did not occur when the Rainscreen was cold, but when an existing fire behind the Rainscreen in the Cladding Cavity had preheated the Rainscreen to a critical temperature. This is illustrated here:

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6. Taplow Tower Fire 2012.

There was an intense flat fire at Taplow Tower in Camden London in 2012 that broke through a window, where the cladding consisted of  Reynobond PE Rainscreen and Mineral Wool insulation (non combustible). The flat was gutted and put out by the fire brigade from the inside. The external cladding only burned up to the next floor level.

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This shows that the rainscreen Reynobond PE does not burn uncontrollably if subjected to an intense fire source. It is assumed here that the cavity fire barriers worked at Taplow Tower, and the fire was prevented from entering or going far into the cladding cavity.

7. Cladding system test of materials used on Grenfell Tower by BRE ~ July 2017.

By July 2017 the BRE (UK Building Research Establishment) were carrying out a “full scale” test on the combination of cladding materials used at Grenfell Tower (as well as othe combinations) using a BS 8414 rig set up, that is used to determine if external building envelope systems (ie cladding) will contain a fire within a compartment (ie flat) for 15 minutes. It is assumed that all the components of the cladding system are installed correctly, including rainscreen, cavity fire barriers and insulation. To pass the test, the internal thermocouples in the cavity and in the insulation on level 2 (which models the next floor up from the fire source), must not reach 600 C for 30 seconds in the 15 minutes after the “crib fire” (which models fire source, peak output 3MW, approx 250Kg of dry pine) starts.

The BS 8414 test on the Grenfell cladding materials was reported by the media as an “absolute fail”. This is illustrated below:

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The intense crib fire burned away a section of the Reynobond PE Rainscreen nearest the source. Flames were observed reaching up to the top of the test rig and sometimes beyond it (flames in natural fires obviously fluctuate). The test was finished after just 7 minutes. The actual results of the fire on the test rig looked like this:

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7. What would a BS 8414 style test with 20 levels look like?

This BRE BS 8414 test does not explain why 20 floors of cladding at Grenfell Tower was on fire in the first 21 minutes. This test proves that a powerful large dry pine crib wood fire can melt the polyethylene core of panels directly above, and the combined fire can burn a large hole in the Reynobond PE Rainscreen. It does not show that under normal fire conditions that the Rainscreen will continue to burn without a large external heat supply (like the wood crib).

Imagine if the BRE had been able to build a 20 floor test rig, the results would look like either the second or third case illustrated in the image below:

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If the BRE had built a 20 floor tall test rig, then after 30 minutes the crib fire would use up all the wood fuel, and the damage to the rainscreen and insulation could potentially  extend to a few floors. This is shown in the second (middle) case in the image above.

The first (top) case in the image above shows how the actual BRE test results would have looked on this enormous test rig.

The third (bottom) case in the image above, shows what actually happened at Grenfell Tower, with the fire racing up 20 floors in 21 minutes. This could only happen, from all the information I and others have seen, if the cavity fire barriers were ineffective AND combustible cladding materials were used, and the fire raced up a 45m chimney behind the rainscreen.

8. Defective design and installation of Cavity Barriers on Grenfell Tower.

There is some evidence that there were gaps in the horizontal cavity fire barriers under the rainscreen at Grenfell Tower. This uses technical planning drawings submitted to the local council and high resolution photographs of the exposed cladding when the refurbishment was finished. This picture below shows gaps in the cladding ventilated cavity fire barrier line on a Grenfell Tower column:

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The rainscreen panels are hung on the small rods bolted across the vertical black aluminum channels, that cut through the horizontal cavity fire barrier line. There is no evidence of fire stopping in these aluminum channels. Also almost all of the height of the columns has a ribbed and grooved surface in the concrete. There is no evidence that these ribs and grooves were firestopped.

I then transposed these air gaps onto a technical drawing of a Grenfell column cross section :

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You can see the ribs and grooves in this concrete column cross section. These air gaps are shown in yellow, and assume to be unprotected. Using the cladding photographs above there are yellow air gaps around the aluminum channels that support the rainscreen panels, these are assumed to be unprotected. Also shown in blue is the 25 mm protected air gap between the ventilated cavity  fire barrier and the rainscreen, which will be closed when the barriers expand with heat (fully closed at 180 C).

The image was created as accurately as possible using a detailed technical drawing to scale. A graphics program scanned the image for yellow and blue pixels. Scaling this up to the real actual scale, an air gap 250 cm squared was protected by cavity fire barrier, while an air gap of 270 cm squared was unprotected, using the assumptions given. If this situation was repeated on other Grenfell cladded columns, then the cavity fire barriers would be essentially useless, as fire bypassed them to flow through unprotected air gaps. [2019: submissions to the Grenfell Inquiry in 2018, by Dr Barbara Lane exposed many more serious defects in the cavity barrier coverage, installation and product selection on Grenfell Tower. In some cases cavity barriers were installed upside down or even the wrong way round]

The picture below shows cladding under a window in a horizontal cladding section between the columns:

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Gaps have been cut in the horizontal cavity fire barrier line to take the vertical aluminum channels.

There also appears to be no vertical firestopping between the vertical cladded columns and the horizontal cladded sections around the flats’ windows, that should have stopped the fire moving sideways from the columns [2019: submissions to Grenfell Inquiry stated only half of the necessary vertical fire barriers around the columns were installed].

9. Defective design and fire-stopping around Windows on Grenfell Tower.

It has also been reported that air gaps were left around the flats’ windows, allowing smoke and fire easy access to enter flats ( https://www.channel4.com/news/grenfell-new-revelations-did-window-renovations-contribute-to-spread-of-fire ). This excellent piece of reporting [2019: confirmed by 2018 Grenfell Inquiry submissions] suggests that the windows of the flats were moved forward by the refurbishment from being in the concrete walls to being in the same vertical plane as the insulation. This allowed smoke and flames direct access to flats by going through the burning PIR insulation. There was no fire stopping around the UPVC windows to stop his happening.

10. Defective internal fire-stopping and smoke extraction in Grenfell Tower.

Internal firestopping at Grenfell Tower needs to be examined as closely as external firestopping. The refurbishment involved removing and installing new pipes in the vertical service risers, that runs vertically through the flats over the entire height of the building. An application was made to remove the internal vertical fire-stopping between flats, and it is not known if this was effectively replaced after the refurbishment ( http://www.insidehousing.co.uk/fire-safeguards-in-grenfell-were-temporarily-removed-during-refurbishment/7020464.article ).

The lift lobbies and the protected stairwell quickly filled up with smoke, preventing many people from escaping. The last resident to escape reported being forced by smoke in his flat into launching himself into the thick smoke outside his flat, and down the stairwell. He thought he was treading on lots of fire hoses, but they turned out to be dead people who had collapsed and died on the stairwell from toxic smoke. The doors of the flats and the doors to the stairwell should have been able to contain fire and smoke for 60 minutes.

There should have been a system to extract smoke from the lobbies and the stairwell. None of this happened. Defective fire stopping from fire doors is a common and very serious problem in social housing tower blocks in London ( https://www.ifsecglobal.com/london-tower-block-fire-councils-social-landlords-ignored-warnings-years ). The refurbishment was completed in 2016, and these new fire doors should have all been installed to the correct standard. Residents of Grenfell Tower were ignored when they complained about botched internal refurbishment of their flats. Was this lack of care also extended to fire doors?

11. Serial botchers of refurbishment of social-housing.

In March 2015 Grenfell residents formed an action committee, and started refusing to allow Rydon contractors access to their flats, due to the unprofessional standard of the work being done ( https://grenfellactiongroup.wordpress.com/2015/03/19/who-you-gonna-call-rydonbusters/ ).

A similar refurbishment project in 2014 also carried out by Rydon at the North Myatts Field Estate in Lambeth in London resulted in a whistle blower inside Rydon writing to the residents association ( https://www.theguardian.com/society/2017/jul/21/the-real-cost-of-regeneration-social-housing-private-developers-pfi ):

rydonWhistleBlowerv2 - Copy

This is about another project by the same company, and does explicitly mention the issue of fire-stopping, fire assessments, emergency lighting and smoke alarms. It suggests a chronic failure of respect for health and safety regulations by Rydon management and its sub contractors.

12. Only non-combustible cladding is adequately safe in the real world.

Currently the UK BRE [July 2017] are doing full scale tests on combinations of rainscreen and insulation. Without effective fire stopping (cavity fire barriers) no combination is safe for use in high rise residential or office buildings. Unprotected cavities in cladding provide a route for fire to travel between compartments (ie flats).

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Only Limited Combustibility Rainscreen (ie Fibre Cement Panels) and Mineral Wool Insualtion should be allowed on high rise buildings. Other combinations are much too  dependent on adequate fire stopping. This is too much “core fire safety”, to hang on correctly installed fire-stopping, which is often hidden, not inspected and botched by low integrity contractors (whose obsessive focus are on costs and profit rather than safety).

These other cladding combinations need to be stripped out and replaced. The choice of cladding materials allowed by building regulation needs to reflect the reality of the lack of respect for UK government regulation among many in the construction Industry ( https://www.theguardian.com/uk-news/2017/jun/15/long-builder-chain-for-grenfell-a-safety-and-accountability-issue ).

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13. Without fire-stopping tower blocks are human incinerators.

The Grenfell Tower would not have been turned into an absolute fire death trap, if fire-stopping was not systematically botched. This central issue must be forcefully pursued by fire engineers reporting to the public inquiry. However this seems very unlikely if construction industry friendly experts are appointed by the inquiry. [2019: Fire-stopping and cavity barriers were investigated and reported on to the inquiry in 2018. The well known fire science experts appeared to avoid meaningful  conclusions, for some reason.] 

This is how the Rapid and Deadly Spread of the Grenfell Tower Fire could have happened:

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14. The legal aspects.

Lastly on the legal side, the UK 1972 Defective Premises Act states that builders have a duty of care to residents of the buildings they build or alter ( http://www.legislation.gov.uk/ukpga/1972/35  ). The Building Regulations 2010 Act in Schedule 1 sets out the requirement for buildings to adequately resist internal and external fire spread ( http://www.legislation.gov.uk/uksi/2010/2214/schedule/1/made ). The UK government has given guidance on how this can be achieved in Approved Document B ( https://www.gov.uk/government/publications/fire-safety-approved-document-b ). There is also the UK Building Control Alliance guidance on the “Use of Combustible Cladding Materials on Residential Buildings” ( http://theriveroflife.com/wp-content/plugins/BCA-Technical-Guidance-Note-18.pdf ), which gives this very relevant advice:

“Within the confines of a cavity, the flame will also elongate up to ten times its length as it searches for oxygen. Hence, the need for robust cavity barriers, restricted combustibility of key components and the use of materials with a low spread of flame rating is necessary, particularly given the delamination and spalling [breaking into fragments] nature of some of the components when heated”

It should be possible to pursue those responsible for the Grenfell Tower Fire disaster for corporate manslaughter (senior managers whose policies led to death and injury, penalty=fines) and gross negligence manslaughter (against individuals whose actions resulted in a failure of duty of care leading to death and injury, penalty=imprisonment).

What is really needed is more whistleblowers. Now is your time.

 

 

Key Points to Creating Justice for Victims of Grenfell Tower Fire Slaughter.

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Key Points to Creating Justice for Victims of Grenfell Tower Fire Slaughter:

[ Posted by Lara Keller 22/6/17 Updated 18/6/19 ] anchorTableSmall - Copy Blog Table Of Contents

1. Tower blocks cannot be rapidly engulfed by fire, without huge lack of fire cavity breaks. Alu-PE panels secondary issue to this.

2. Huge number missing hidden fire cavity breaks, means criminal gross negligence manslaughter by number of individuals.

3. This requires a major focused aggressive fast moving police investigation. Evidence secured and people interviewed and arrests made.

4. Outcome of investigation probably be used as major embarrassment to UK Conservative Government and RBKC Council, this is a risk to senior police officers careers.

5. Justice for Grenfell victims therefore requires brave influential champions, supported by demonstrations of constructive public anger.

Supporting sources:
See:

  1. “If regulations were followed, the Grenfell Tower inferno should have been impossible.” 14/6/17 Geoff Wilkinson, building inspector, UK Daily Telegraph.  http://www.telegraph.co.uk/news/2017/06/14/regulations-followed-grenfell-tower-inferno-should-have-impossible/  to get accessible copy see https://partnershipblog.wordpress.com/2017/06/19/if-regulations-were-followed-the-grenfell-tower-inferno-should-have-been-impossible/
    Highlighted Key Paragraph = “Something similar happened in Irvine [Irvine, North Ayrshire, Scotland] in 1999, after which new regulations were put out which limited the types of cladding which could be used. In particular, they mandated barriers at various points in the cavity, blocking off the ‘chimney’ on all sides. And in 2014 Grenfell’s landlords decided to install exactly this kind of cladding in order to ‘improve its appearance’ when viewed from the luxury flats nearby. The Guardian has reported that some panels used in modern cladding are only fire-proofed on the surface, behind which is up to 30cm of highly flammable polyurethane. If true, that is a major non-conformance with regulations. But even if not, were the proper firebreaks put in place behind the panels?
  2. UK Building Research Establishment (BRE) presentation on “The Fire Performance of Building Envelopes”, June 2016 https://www.ifsecglobal.com/wp-content/uploads/2016/07/The-Fire-Performance-of-Building-Envelopes-by-Steven-Howard-BRE-Global.pdf Highlighted Key Slide =
    External Walls over 18m in Height. A summary of [guidance from Approved Document B, 2007] Volume 2 Section 12:
    * External surfaces comply with Diagram 40 ‘Euroclasses’. Applicable to all Buildings. Additional recommendations for buildings with a storey over 18m: All insulation and filler materials should be A2-s3,d2 or better. All cavity barriers and fire stopping guidance needs to be followed.
    OR
    * Test the complete system to BS 8414.
    Note = Also gives introduction to fire spread in cladding systems, and useful list of previous incidents.
  3. “Manslaughter charges under consideration after Grenfell Tower disaster.” 18/6/17 See (is accessible):  http://www.telegraph.co.uk/news/2017/06/18/prosecutors-considering-manslaughter-charges-grenfell-tower/  Extract= “He [Sir Keir Starmer, Labour Shadow Brexit Minister]said they would be looking at whether anyone could be charged with manslaughter following a litany of failings that led to the disaster – in which at least at least 58 people are now feared to have been killed.”
  4. “Grenfell renovation proposed temporary removal of fire protections.” 16/6/17 https://www.insidehousing.co.uk/fire-safeguards-in-grenfell-were-temporarily-removed-during-refurbishment/7020464.article to get accessible copy see: https://partnershipblog.wordpress.com/2017/06/19/grenfell-renovation-proposed-temporary-removal-of-fire-protections/ Key Extract = “To install the new pipes, the ‘fire stopping’ – systems used to seal openings and joints to prevent the spread of fire – would have had to be partially removed, under the ‘preferred option’ listed in a report from 2012 by engineers Max Fordham. The document said this option was adopted.” [Key Question=Were the fire cavity breaks replaced around the 6 x vertical service risers in Grenfell Tower, creating internal chimneys for inter-flat fire spread?]
  5. “Gross negligence manslaughter” 14/8/13 https://app.croneri.co.uk/feature-articles/gross-negligence-manslaughter Useful guide to offenses of gross negligence manslaughter compared to corporate manslaughter.
    Key passages = “The police investigate suspected cases of manslaughter. Prosecution decisions are made by the Crown Prosecution Service in England and Wales, the Crown Office and Procurator Fiscal Service in Scotland and the Director of Public Prosecutions in Northern Ireland. The Health and Safety Executive is involved through a joint approach to work-related deaths between all the relevant regulatory authorities in line with the principles of the Work-related Deaths Protocol.”
    “The maximum penalty for those convicted of gross negligence manslaughter is life imprisonment. The factors which may be involved in deciding the length of any prison term include whether:
    * multiple deaths were involved,
    * the case involved a prolonged and dangerous course of conduct,
    * there was an awareness of a significant risk of death or really serious injury,
    * warnings had been ignored,
    * the defendant was pursuing a course of conduct for financial gain.” [Note = to see “duty of care” requirement between construction professionals and tenants, see Defective Premises Act 1972 http://www.legislation.gov.uk/ukpga/1972/35/pdfs/ukpga_19720035_en.pdf ]


     

If regulations were followed, the Grenfell Tower inferno should have been impossible.

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If regulations were followed, the Grenfell Tower inferno should have been impossible.

[ Posted by Lara Keller 19/6/17 Updated 18/6/19 ] anchorTableSmall - Copy Blog Table Of Contents

[ Source= June 15th, 2017 UK Daily Telegraph, by Geoff Wilkinson, https://www.telegraph.co.uk/news/2017/06/14/regulations-followed-grenfell-tower-inferno-should-have-impossible/ ]

If regulations were followed, the Grenfell Tower inferno should have been impossible

I am a building inspector and fire engineer with 30 years’ experience. I’ve overseen numerous projects across London, including new builds and refurbishments, making sure buildings comply with the proper regulations, and post-occupation fire risk assessments. Given my experience, I was shocked by the blaze which engulfed Grenfell Tower in the early hours of Wednesday morning.

At this point in time it’s very hard to tell precisely what went wrong. We don’t know where the fire started and we don’t know how it spread. What we can say for sure is how the building should have performed – and that it definitely did not perform that way. If regulations were followed, what happened at Grenfell Tower should never have been possible, and there are very big question which need to be answered. There are already suggestions that proper planning procedures were not followed.

Normally, British fire regulations assume that fires will start in one location only – and normally, this is completely reasonable. In a big tower block like Grenfell, each individual flat is a fire-tight box from which flames should not be able to escape, and a fire which starts in one tends to stay in it. That is why residents are usually advised to stay within their own rooms and wait for rescue. The fire service should arrive within ten minutes, ascend the building, and tackle the fire where it burns, while other residents sit quite happily in place.

This is also why we shouldn’t be disturbed by reports from Grenfell that there was no common alarm system installed. Most residential blocks don’t have common alarms, because they could trigger a mass panic in which everyone tries to evacuate via the same stairwell which the fire service are using to reach the fire. Unlike in a hotel, there are no fire trained fire wardens to safely direct such an evacuation. In the event that a fire grows too large, firefighters might sometimes decide to evacuate the floor immediately above. Otherwise, it’s better everyone stays where they are. That policy has worked several hundred times over the past few years without a problem.

What happened at Grenfell was something else entirely. Firefighters were on site six minutes after being called, which is within expectations. But it is extremely unusual for the fire to spread this far and with this speed and ferocity. Within half an hour or so it had travelled way beyond the first flat, making it very difficult for the fire services to control it. Even more worryingly, survivors have reported that stairwells and lobbies were choked with smoke, which should never happen: there are supposed to be means of clearing smoke from such areas. In those circumstances, “stay and hide” becomes obsolete.

And yet to me the fire spread still had a horrifying familiarity. This has happened before, and – if we are not careful – it may happen again.

In Knowsley Heights in Manchester in 1991, fire spread in a way no one had predicted via the decorative cladding on the outside of the building. These plastic or metal panels are installed to protect a building from weather or improve its appearance, but between them and the wall there is a cavity where rain can run down. In the event of a fire this acts like a chimney, drawing the hot air up through itself and making the flames burn brighter. In this way fire travelled all the way up from the base of the building to the very top.

Something similar happened in Irvine in 1999, after which new regulations were put out which limited the types of cladding which could be used. In particular, they mandated barriers at various points in the cavity, blocking off the “chimney” on all sides. And in 2014 Grenfell’s landlords decided to install exactly this kind of cladding in order to “improve its appearance” when viewed from the luxury flats nearby. The Guardian has reported that some panels used in modern cladding are only fire-proofed on the surface, behind which is up to 30cm of highly flammable polyurethane. If true, that is a major non-conformance with regulations. But even if not, were the proper firebreaks put in place behind the panels?

Once spread via cladding, the fire could have caught on curtains blowing through windows left open on a hot summer’s night. Again this is believed to have been a factor in the Lakanal House fire in 2009. That disaster occurred on a very similar night to this one.

Even if this proves to be correct, however, the building should still have been safe. For the fire to spread internally after that point it would still have to get through the fire door in the individual room, through another fire door at the front of the flat, and through yet more doors in the corridor outside. Clearly there has been a failure of multiple systems: for one to fail is perhaps understandable, but for so many to have failed all at once, in the modern era, is entirely unheard of.

The investigation will of course look into this. But another explanation may lie in reports, as yet unsubstantiated, that works were recently carried out to the gas main that runs vertically up the building. If the contractors carrying out those works did not replace the necessary fire protection after finishing, that would be an easy way for fire to spread. Anything that creates a path for fire can and will be used in that fashion. Even a drill-hole of four inches in diameter can be enough. And if there are combustible materials in ducts – plastic pipes, plastic wires – flames can creep rapidly through a building without the fire service even knowing.

The Lakanal House fire led to specific recommendations. All landlords were given clear, copious information on fire precautions and told to undertake regular risk assessments. People like me then go around the tower blocks checking for ducts that need to be blocked or cladding that needs to be fixed. The problem is that we never really know whether the works we recommend are actually carried out, or, if they were, how long they took. There is no easy way to check whether landlords have carried out their duty.

Worse, there is an ongoing issue around contractors who don’t understand what they need to do to ensure fire safety. Anyone who the landlord allows to alter or amend a building, in any way, shape or form, must be made aware of which walls are fire walls and which materials need to be replaced after they’re done. That, too, doesn’t always happen.

We shouldn’t overstate the danger. There are literally thousands of blocks like this across the UK and there are probably several hundred fires which start in them every year. These fires usually don’t spread and are dealt with in exactly the expected fashion; more people probably die in fires in two- or three-storey houses than in tower blocks.

Nevertheless, the standard of safety across London is highly variable. Some landlords are right on top of it, and act on issues that are reported within a matter of hours. Others don’t give fire safety the priority that it requires.

What’s frustrating is that we are all familiar with going into a toilet block and seeing a register on the wall to show that someone has gone round to check it is clean. There’s no such process for fire safety. Perhaps we need to make landlords post evidence of regular risk assessments in communal areas so residents can see exactly what has been checked and what hasn’t. Or perhaps we need to give fire brigades the resources to conduct building inspections themselves, as they did back in the 1970s. Nowadays, buildings are effectively self-certified.

Whether regulations and recommendations were followed in this case will come out in the wash. But indications on the council’s website indicate the building was approved on a “building notice”. This type of fast track planning application saves the need to submit detailed proposals and plans to the building inspector and relies on the experience of the inspector to recognise and approve the works by eye. This type of application is wholly inappropriate for large complex buildings and should only be used on small, simple domestic buildings.

Nobody can turn around after Knowsley, Irvine and Lakanal and say they didn’t know there were risks. The guidance was there, the instructions were clear, and we knew the problem. The question is now whether we will do anything about it.

[Geoff Wilkinson is the managing director of Wilkinson Construction Consultants]

[ Source= http://www.telegraph.co.uk/news/2017/06/14/regulations-followed-grenfell-tower-inferno-should-have-impossible/ ]