London fire: Grenfell Tower's design helped spread blaze up the outside, experts say

The cladding used on the outside of the building can work like a chimney

The design of Grenfell Tower might have helped the deadly fire that ripped through it spread, according to experts.

The building was covered in cladding that spread the fire quickly up the entire 24-storey building, according to architects and firefighters.

"The cladding was clearly spreading the fire," said Mike Penning, a Conservative MP who worked as a firefighter and then fire minister. "We need to find out what went on."

The kind of rainscreen cladding used on the outside of the building has cavities inside of it which can work as chimney – carrying the fire up the building. It seems to have been added last year, as part of refurbishment work.

Residents agreed that the material on the outside of the building appeared to be allowing it to spread up the outside. They suggested it had been added in part to make the housing block look better from the outside, as part of a regeneration plan linked to the building of luxury flats nearby.

Paul Mennacer, who lived on the seventh floor of Grenfell Tower, said: "I got woken up by people screaming, saying 'Don't jump'. There was black smoke coming at me and my instinct told me 'Just grab your shoes and run out'.

"It was hard to get out because the fire exit stairwell was on the side of the fire and so there was a lot of debris falling.

"It was the cladding that was on fire and that's what was burning, people believe that it was the cladding."

Journalist Jack Monroe, who worked in the fire service, tweeted that "Whoever signed off on that cladding needs to be hauled before a court and held fully accountable for every single fatality and injury".

Some residents and experts also suggested that the renovation work may have used non-flammable cladding. That is cheaper to install but can create a fire risk.

Chartered surveyor and fire expert Arnold Tarling, from Hindwoods, said that the process can create a 25mm-30mm cavity between the cladding and the insulation.

"It produces a wind tunnel and also traps any burning material between the rain cladding and the building.

"So had it been insulated per se, the insulation could fall off and fall away from the building, but this is all contained inside."

He said not all insulation used in the process is the more expensive non-flammable type.

"So basically you have got a cavity with a fire spreading behind it."

Angus Law, of the BRE Centre for Fire Safety Engineering at the University of Edinburgh, said: "Early media reports suggest that this event has similarities with other fires that have occurred recently around the world."

He added: "The UK's regulatory framework for tall residential buildings is intended to prevent the spread of fire between floors and between apartments.

"If spread of fire does occur, as has happened at Grenfell Tower, the consequences are often catastrophic."

If the cladding was indeed to blame for spreading the fire, it would explain why the damage was so universally spread over the outside of the building. It would also lead to questions about how the building was built and renovated.

The firm that provided the cladding for the Grenfell estate was Harley Curtain Wall, according to the Architects Journal. That firm went into administration two years ago.

Rydon Construction, which refurbished the building in works that finished last year, said that it was confident that the construction was up to standards. It said it was "shocked to hear of the devastating fire" but that all the work "met all required building control, fire regulation and health & safety standards".

The building was refurbished recently at a cost of £8.6 million, with work completed in May last year.

The exterior of the tower was modernised with cladding and replacement windows, while additional homes were added using vacant space in the building.

On its website, Rydon Construction said: "Externally, rain screen cladding, curtain wall facade and replacement windows were fitted, improving thermal insulation and modernising the exterior of the building."

The work also included the installation of new double-glazed windows and a new communal heating system.

A communal entrance was also created along with new facilities for returning tenants, Grenfell Under 3s Nursery and Dale Youth Amateur Boxing Club.

Based in the borough of Kensington and Chelsea, it is around half a mile from the Westfield shopping centre and close to many London Underground stations.

Additional reporting by agencies