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Grenfell Tower Inquiry diary week 42: ‘They would leak as much as they leaked. They were what they were’

Insight09.07.212.30 PM by Peter Apps

The Grenfell Tower Inquiry continued its in-depth investigation of the tower’s non-compliant smoke control system this week, with evidence from the various contractors involved in delivering it. Peter Apps reports

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Let’s start with a little background. Since its construction in 1974, Grenfell Tower had been fitted with a smoke control system.

These were essentially four chimneys running through every residential floor of the tower, with vents on each landing. The idea is that in a fire, these vents open on the fire floor and stay closed everywhere else, with the smoke funnelling out through the chimneys instead of spreading around the building.

The inquiry has already learned that this system went wrong during a fire in 2010, when the vents on upper floors leaked smoke sucked up from a fire on the third floor, causing inhalation injuries to three residents.

An investigation led to the conclusion that the system was broken “beyond economic repair” and required replacement, with an enforcement notice served by London Fire Brigade inspectors in 2014.

But it took until 2016 for this work to actually be carried out – and it was this process and the ultimate effectiveness of it that we were investigating this week. We can begin the story in 2012.

‘Our intention was to make the system as good as we could within the constraints of the tower’

At this point, the refurbishment of the tower was in its embryonic stages, and a design team that was working on a new school and leisure centre had been tasked with sketching out the basic ideas by building manager Kensington and Chelsea Tenant Management Organisation (KCTMO).

One of these was an engineering consultancy called Max Fordham, which was asked to review plans already prepared by another consultancy, AECOM, to upgrade the smoke system.

There was immediately a problem. The chimney shafts through which smoke was supposed to exit the building were too narrow. They had been built 0.48 square metres wide instead of the required 1.5 square metres.

The decision was taken not to remedy this defect – which would entail an enormous and disruptive construction effort – but to make the system “as good as we could within the constraints of the tower,” in the words of Matt Cross Smith, an engineer at Max Fordham at the time (pictured above).

Max Fordham picked up the AECOM designs and incorporated them into the refurbishment plans in November 2012: they would extend the vents downwards to reach the additional residential floors being added by the refurbishment and install a new mechanical extract system, using large fans to blow air through columns on one side and suck it out on the other. This is known as a ‘push/pull’ system.

‘It’s a bit like the old quart into a pint pot’

Max Fordham asked a specialist contractor called PSB UK to look over the designs it had proposed.

PSB was not formally contracted at this point, but this sort of informal work was said not to be uncommon – on the understanding that it will lead to the contract to do the job later on.

However, Hugh Mahoney (pictured above), former commercial manager at the contractor, did not believe that this system would work. The narrow shafts would not be able to accommodate all the air that would be sucked in by the fans in the ‘push/pull’ system.

“It’s a bit like the old quart into a pint pot,” he said. “You’re trying to push too much air through a small hole.”

As a result of this, he did not feel that he could design a system for the tower that complied with guidance.

“You could not put forward any system that would comply with any of the guidance,” he said. “It was impossible. So therefore we, as designers, looked at it from a different direction and said, ‘Well, the spirit of the standard is to protect the stair; can we come up with an alternative design?’”

The new system he designed was bespoke: all four columns would be used to extract smoke, with air blown across the door to the stairwell.

This would – it was hoped – create the right pressure conditions for smoke in the lobbies to disperse through the open vents instead of spreading into the stairwell.

“Are you aware of any other high-rise residential building that you’ve worked on that has a smoke control system like this one?” asked counsel to the inquiry Kate Grange.

“Absolutely not,” he replied. “As I said, it was an alternative solution to try and reach the spirit of the standard, because we couldn’t achieve it in the standard way. It was impossible to put a standard system in because of the employer’s requirements.”

‘Doesn’t that indicate this was an unrealistic design assumption to make?’

This new system was not perfect. One issue was that the calculations of air pressure he made for the operation of the system assumed all of the six flat entrance doors in the lobby would be closed, and the doors to the stairwell would be the only ones that opened.

An expert report by Dr Barbara Lane says that this situation never actually occurred on any floor on the night of the fire.

“Doesn’t that indicate that one single stair door being open and all other doors being closed was an unrealistic design assumption to make?” asked Ms Grange (pictured above).

Mr Mahoney said that government guidance makes this assumption and that it was “not unique to Grenfell Tower”.

“She [Dr Lane] needs to write to the Approved Document B governing body and get them to change the standards,” Mr Mahoney said.

Mr Mahoney robustly insisted that the new design constituted a “betterment” of the existing conditions, rather than a replacement system in its own right.

He said his role, as a result, was merely to ensure that the new system was an improvement on the one that had been there when he started.

‘We’d been appointed… [to] fulfil that role as middleman, conduit for information’

In March 2014 – as the inquiry has examined at great length back in an earlier phase – Rydon was appointed lead contractor for the refurbishment job.

Rydon then appointed JS Wright as the sub-contractor responsible for the ‘mechanical and electrical’ elements of the work. And JS Wright further sub-contracted to PSB UK to work up the design proposals that it had informally prepared for Max Fordham.

To complicate the position further, JS Wright contracted another firm, RJ Electrical, to work on the actual installation of the new components. Max Fordham, meanwhile, remained involved as an advisor to KCTMO, and fire engineering consultancy Exova continued to provide ad hoc advice to the project despite not having a formal contract.

This messy web of companies made the process of tracking various decisions and responsibilities laborious and contradictory.

So who was supposed to check if the designs produced by PSB were compliant?

Alan Whyte (pictured above), senior contracts engineer at JS Wright, said the firm was merely a “middleman” that simply provided a “conduit for information from the specialist back to our client for review, approval”.

“To scrutinise a specialist sub-contractor, I think we’d have to have the in-house capability to be that specialist sub-contractor,” he said.

He said he expected “Max Fordham and building control” to pick up any defects in the design. He said his “understanding of how the chain of command worked” was that Max Fordham would seek and arrange approval from building control.

However, Mr Cross Smith (of Max Fordham) said the responsibility was JS Wright’s, claiming that following the company’s appointment, “the design of the [smoke ventilation system] was now in the hands of [JS Wright] who were taking the lead with building control”.

With regard to the negotiations with building control, in June 2015 PSB presented a technical submission for review which said that the system was “not [designed] to comply with all the requirements of the aforementioned Code of Practice”.

This worried the building control inspector, Paul Hanson. An internal PSB email shows a colleague of Mr Mahoney writing to tell him: “He wants us to basically delete it as it doesn’t tie in with what we have discussed with him. If we can respond quickly, we can avoid him rejecting the [submission].”

The line was ultimately deleted. “As I understand your evidence, [the system] wasn’t designed to comply with all the requirements of that code of practice, so why wasn’t that a statement that needed to be in there?” Ms Grange asked.

“Because we discussed it with all the relevant parties and they were happy with it. They understood after my discussions,” said Mr Mahoney.

‘They would leak as much as they leaked. They were what they were’

A further problem with this system was the ‘dampers’. These are the mechanical devices that open and close to either allow smoke in on the fire floor or prevent it from seeping out higher up the building.

These come in various categories, and the type that Grenfell’s system was fitted with – fire dampers – was the lowest available standard and not designed to prevent the leakage of smoke.

Mr Mahoney said they were selected because higher quality dampers were not designed to sit within the type of vents in use on the system within Grenfell Tower.

“As the other products… on the marketplace would not fit the application that we had, and we had a betterment requirement, this was the best that we could offer, and that’s what we used,” he said.

“Did you explain that to building control?” asked Ms Grange.

“No, but they knew what they were getting,” said Mr Mahoney.

“How could you be satisfied that the dampers that you selected wouldn’t leak excessively?” asked Ms Grange.

“They would leak as much as they leaked. They were what they were. What do you mean by excessively?” said Mr Mahoney.

Asked if he had assessed the suitability of the dampers selected by his sub-contractor, Mr Whyte of JS Wright said he believed this would be done by Max Fordham.

“They were the consultant and that was my understanding of their role,” he said.

But Mr Cross Smith said he did not believe this was the case, saying he saw his role as “in general terms, keep tabs with what was going on in the project and reporting back [to KCTMO]” but he “wasn’t checking, certainly not things like the detail of the components that had been specified”.

Mr Whyte said this had “come as quite a shock” to him when he heard Mr Cross Smith’s evidence.

The evidence is that dampers did leak on the night of the fire – and from quite an early stage. Dr Lane’s expert report quoted residents who witnessed smoke leaking out of vents on the sixth, 20th and 23rd floors from as early as 20 minutes into the fire.

‘Do you accept that could have a misleading effect on either the purchaser or, for example, building control?’

So what were they doing on the market and why were they sold for use on Grenfell Tower?

This question was primarily explored with Roy Jones (pictured above), technical director at Gilberts UK – the supplier that sold the ‘Series 54’ component to PSB.

In a technical explanation of the testing of the products, he explained that the ‘fire dampers’ were not supposed to limit smoke leakage and were instead supposed to retain their integrity in a fire.

The dampers were tested by Exova in October 2011, and sure enough failed the criteria for smoke leakage – both in an ambient test and during a mock fire.

“It was not an aspiration for us at the time to achieve a smoke leakage for this type of damper, it was only to achieve an integrity,” said Mr Jones.

But this is not what the team who purchased them for use on Grenfell Tower was told. Instead, the quote sent to PSB said that the dampers “lasted over 60 minutes for both fire integrity and smoke leakage but [have] no formal certification”.

“In light of your evidence and what we see on the page about the test, it’s not right, is it, that it lasted for 60 minutes in terms of smoke leakage?” asked counsel to the inquiry Alex Ustych.

“You’re absolutely correct, yes, that’s an error,” said Mr Jones.

“Do you accept that could have a misleading effect on either the purchaser or, for example, building control, who might be reviewing those additional notes as part of their assessment?” asked Mr Ustych.

Mr Jones said he did accept that, but added the “caveat” that the product was nonetheless compliant with guidance for the type of damper it was. He said the error was a result of copy and pasting an earlier mistake from a product brochure.

‘We’d have had to go up and down 25 floors every time we did one damper’

After the new system was installed, PSB ran checks to ensure the dampers were opening and closing correctly on each floor.

This process was led by Granville Partlow (pictured above), commissioning and sales manager at PSB. His checks involved activating the system and ensuring the dampers opened and closed on each floor as required.

This checking was partially hindered because grilles were already installed with anti-tamper screws, meaning Mr Partlow had to peer through with a torch to ensure the devices were properly closed.

He said the system was activated “probably a hundred” times to ensure it was working correctly.

But actually, what he was doing was reviewing a laptop that told him whether a signal was being sent to the dampers to close – not physically checking each time.

He said this was because “we’d have to go up and down 25 floors every time we did one damper”. So if a damper was being sent a signal but not operating, he would not have known.

He said he went up at the start and end of the day and checked all of them to ensure they were closed – and this would have alerted him to any that were jammed.

The inquiry has previously heard that concerns were raised about the system just days before the fire in June 2017, with David Hughes of Rydon alerting JS Wright to the fact that the dampers had not opened as they should have in ‘environmental mode’ (when it functions simply to ventilate the building, not as a fire safety device).

A purchase order was raised for PSB to check the system on 12 June, just two days before the fire. It was signed by Mr Whyte, but he said he was unsure precisely what had happened as a result.

What’s next?

Next week will begin with witnesses describing gas works to the tower. This phase of the inquiry still needs to hear from factual witnesses concerning gas, lifts and fire doors, as well as three expert witnesses: Beryl Menzies (on building control), Colin Todd (on fire risk assessment) and Dr Barbara Lane (on the entire module).

It was due to finish in the week commencing 26 July, but is around two weeks behind its original schedule.

This means it will now complete shortly after the summer break, in early September, when we will also hear closing submissions from all parties for all the evidence the inquiry has heard so far.

Investigations will then move to the London Fire Brigade and central government.

Grenfell Tower Inquiry: week 42 headlines

Sub-contractor claims it was 'middleman' and did not check compliance of Grenfell smoke control system

The sub-contractor responsible for the electrical work on Grenfell Tower did not check the compliance of the smoke control system it was charged with overseeing, claiming that it was merely a “middleman” in the construction project.

Grenfell smoke dampers sold with misleading testing information, inquiry hears

Devices designed to close the vents in the smoke control system at Grenfell Tower were sold with a “misleading” assurance that they had been successfully tested to prevent smoke leakage, the inquiry into the fire heard.

Grenfell smoke control system did not comply with guidance and was untested on other buildings

The smoke ventilation system used in Grenfell Tower did not comply with official guidance and had never been employed by the designers on a previous building, the inquiry into the fire heard today.

Grenfell Tower Inquiry phase two: weekly diaries

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Week one: A vivid picture of a broken industry

After a week of damning revelations at the opening of phase two of the Grenfell Tower Inquiry, Peter Apps recaps the key points