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Grenfell | More rigour and greater transparency needed

Grenfell Tower fire

In a special report on the Grenfell Tower fire, New Civil Engineer says new legislation is urgently needed.

The August edition, published today, outlines five key actions that must be acted upon now to ensure a tragedy such as Grenfell never happens again. These are:

1. Establish a government-backed National Fire Risk Assessor Register

2. Make it mandatory for tall building owners to employ only assessors on the National Fire Risk Assessor Register to carry out assessments

3. Require annual assessments to at least Type 1 level, and Type 2-4 level assessments as appropriate

4. Require Fire Risk Assessment Reports to be put into the public realm

5. Set minimum periods for essential remedial works to be completed

What happened at Grenfell Tower was a major tragedy that will trigger seismic shifts in attitudes to tall building safety.

It will have a much more fundamental impact on society as a whole and the construction industry in particular than the 1968 Ronan Point disaster, where the key learning was a greater technical understanding of progressive collapse.

This is no time for knee jerk reactions, quick fixes or media-friendly gestures. In the end, it is the government that must take responsibility; it is the government that must bring about the major improvements in fire safety legislation that are so obviously needed.

So far, much of the public focus has been on the overcladding system. The media has whipped up a storm, spreading alarm and despondency among the many thousands of tower block residents in the UK. In response, the government has ordered mass testing of cladding on similar public buildings, and as New Civil Engineer went to press, all 200 of the samples have failed the BRE’s new simple screening test. More complex testing has been ordered. Overcladding is being ripped off. Tower blocks have been evacuated.

Obviously the performance of the overcladding was a factor. But the inconvenient truth is that fire would almost certainly have spread up the façade of the tower even if the overcladding was totally fire resistant, even if the overcladding had never been fitted. It might well have spread more slowly, giving more people time to escape, but vertical external spread was virtually inevitable.

The mechanisms of external vertical spread are well understood. If a fire breaks out in a flat or on an office floor and there is no sprinkler system to snuff it out, its progress is rapid and terrifying. Furniture, carpets, curtains, soft furnishings, TVs and computers, paper in all its forms, begin to heat up rapidly, giving off combustible gases as they do so.

Once internal temperatures reach around 600°C, these gases near simultaneously ignite in a process known as “flashover”. Temperatures rapidly climb to in excess of 1,000°C. Long before this, the external window will have collapsed, and flames will be licking up the façade above.

The Coanda effect will ensure the flames hug the facade of the building. Should there be another floor above the source of the fire, thermal radiation from the external flames will pass through the glass of any window and ignite anything flammable inside. Windows will shatter, uPVC window frames will be destroyed. In the case of Grenfell Tower, the first that many sleeping residents might have known would have been their closed curtains bursting into flame.

They would have had only minutes to escape. Soon flames from the second burning flat would be roaring up the façade, igniting the flat above in its turn. And so it would go on, floor by floor.

But in most cases of fi res in high rise residential buildings the flames are confined to the flats directly above the source of the fire. Horizontal spread externally or internally is virtually unknown in developed countries. Open plan office floors obviously behave differently.

Images from the early hours of 14 June indicate that the “vertical” spread was not always strictly vertical – the wind was deflecting the flames from the vertical in the downwind direction. They also show vertical external spread on more than one façade.

This implies that the fire both progressed sideways, flat to flat, and broke out of flats into the central lobby, penetrating into and igniting more flats, which then sent more flames out and up hitherto untouched facades. One by one, flats that were initially remote from the fourth floor outbreak burst into flame, until all four façades of the tower were burning.

There are several unknowns that need to be addressed here. First the obvious. What exactly was the contribution of the overcladding, how much did it accelerate the rate of vertical fi re spread? Only an exhaustive programme of research and testing to BS8414 – 1 and beyond can provide authoritative answers to those questions.

The refurbishment included new heating and hot water supplies to the flats, which involved retrofitting pipes. Gas supplies were upgraded last winter, gas pipes were in the process of being boxed in with fire resistant materials. A smoke ventilation and extraction system was installed. Yet the shocking stories told by survivors immediately after the disaster suggest that all was perhaps not as it should have been.

Which brings us to the key questions. Was all the crucial firestopping present and in good condition? Were all doors up to fire safety specification? Was the smoke ventilation and extraction system fit for purpose? A completion certificate was issued by building control after the refurbishment – but what did it cover?

A completion certificate was issued by building control after the refurbishment – but what did it cover?

A good example of how residential towers should react to fires is last year’s blaze in the 18 storey Shepherd’s Court building in west London.

A faulty tumble dryer started a fire on the 7th floor. It broke out, igniting the cladding above the window and starting a blaze in the flat above. By the time the flames had spread up to the 11th floor the fire brigade had arrived, and the fires were soon extinguished.

There was no internal breakout from the original flat or those above it. Nor were there any deaths or serious injuries. There are several other similar UK examples, including the 2005 Harrow Court blaze in Stevenage.

A rather different but still very relevant story is that of the 2009 Lakanal House fire in Camberwell, south London.

Six people died after a fire started on the ninth floor of the 14 storey residential tower, which dated from 1959. A recent £3.5M refurbishment had been designed to bring the building up to current fire safety standards: nevertheless, fire spread rapidly throughout the upper storeys.

At first the cladding was suspected, as it had reportedly burned through in less than five minutes. The inquest into the six deaths, however, concluded that a series of “botched renovations” over the years had led to the firestopping between flats and corridors being removed. There have been reports that there had been no proper fire risk assessment carried out on the building since responsibility for fire safety was transferred from the London Fire Brigade to the local authority in 2006.

Similar stories from elsewhere have been emerging since the Grenfell Tower tragedy. Communities secretary Sajid Javid told Parliament that during post-Grenfell inspections of tower blocks in Camden, the fire service found multiple fire safety inspection failures. These included problems with gas pipe insulation, some inaccessible stairways, breaches of internal walls and hundreds of missing fire doors. Three of the Camden towers have been evacuated. The council’s work includes installing new fire boarding and re-insulating some pipes.

All this appears to reveal that the new era of self-assessment and freedom from burdensome bureaucracy allegedly created by the Regulatory Reform (Fire Safety) Order 2005 is something of a shambles. Industry experts have told New Civil Engineer that after years of austerity, cash-strapped councils routinely outsource fire risk assessments to private providers, allegedly too often on the basis of lowest quote. And when serious deficiencies are reported, corrective action is not always guaranteed.

To make matters even worse, there is no mandatory minimum standard of fire risk assessor expertise and no requirement for formal qualifications or independent certification.

Much could be learned from the system that has ensured that no UK resident has died as a result of a collapsing dam since 1925, despite there being more than 2,000 large dams in England, some of them very old. The government, through the Environment Agency and the ICE’s Reservoirs Committee, appoints appropriately qualified engineers to one of four panels. These panel engineers, as they are known, certify the safety of every large dam at intervals of 10 years or less, and prepare a yearly written statement about the condition of every large dam.

At present there are approximately 180 panel engineers. A similar scheme for the fire safety of tall buildings would obviously need more qualified assessors, but is eminently achievable. It could be run in conjunction with a specialist institution, which would be responsible for assessing the assessors on behalf of the government.

A National Fire Risk Assessor Register, why not? Make it mandatory for tall building owners to only use assessors from the register, include requirements for remedial action to be carried out within stated periods. And why not follow the example of some enlightened councils, such as Hammersmith & Fulham in west London, and insist that assessment reports are made available online?

Tenant associations would really appreciate that. It would enable them to monitor the response of the building owner and bring pressure to bear if remedial action is delayed. This would indeed be a seismic shift in fire safety legislation – but after the Grenfell Tower tragedy, a seismic shift is the least we should expect. Or settle for. 

  • Dave Parker is New Civil Engineer’s technical editor emeritus, an ICE Fellow, a published author on tall buildings and was instrumental in the creation of confidential structural safety reporting system CROSS.

FIRE RISK ASSESSMENTS

Under the Regulatory Reform (Fire Safety) Order 2005, which came into force in October 2006 and which applies only to England and Wales, responsibility for fire safety inspections was removed from local fire brigades and transferred to the building owner.

There are now four grades of fire risk assessment that may be needed to satisfy the Order.

A Type 1 assessment is confined to nondomestic communal spaces and is largely visual. This is by far the most common assessment routinely performed. In Scotland the law is different – there is no obligation to assess residential tower blocks at all

A Type 2 assessment is also confined to the communal spaces, but can involve “destructive exposure” to allow firestopping to be checked.

A Type 3 assessment is non-destructive, but involves inspections of at least a sample of flats

A Type 4 assessment is similar to a Type 3 assessment, but involves destructive exposure.

 

Readers' comments (1)

  • "Obviously the performance of the overcladding was a factor. But the inconvenient truth is that fire would almost certainly have spread up the façade of the tower even if the overcladding was totally fire resistant, even if the overcladding had never been fitted. It might well have spread more slowly, giving more people time to escape, but vertical external spread was virtually inevitable."

    Really? According to (unofficial) reports, the fire service had extinguished the internal fire, but were surprised to find that cladding had been ignited and was spreading the fire vertically. Are you seriously suggesting an internal fire which could be extinguished in a reasonably routine manner would have spread if the building had not been clad?

    And as for the media whipping up a storm, yes they have and quite rightly so. If they had not, what would be happening now? Complacency seems to have been rife in the industry and government. A kick up the backside is sorely needed, administered with a very large boot. The criminal investigation may possibly deliver that, but I suspect that will take so long that those who might be considered blameworthy will have found a very large rock to hide under.

    Public confidence needs restoring now and well meaning platitudes will not do it.

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