Grenfell cladding panels were primary cause of external fire spread, inquiry hears

News04.06.182.45 PM by Luke Barratt

The cladding panels installed on Grenfell Tower in the 2012-2016 refurbishment were the primary cause of the fire spreading up the outside of the building, the official inquiry has been told.

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Grenfell’s cladding panels were primary cause of fire spreading up outside of building, inquiry has heard #ukhousing #GrenfellInquiry

First expert witness report given at the #GrenfellInquiry #ukhousing

Professor Luke Bisby, an expert witness to the Grenfell Tower Inquiry tasked with examining how the external facade of the tower caught fire and how the fire spread over the facade, made his first report today.

Professor Bisby wrote: “The primary cause of rapid and extensive external fire spread was the presence of polyethylene-filled ACM rainscreen cassettes in the building’s refurbishment cladding system.”

This conclusion was based largely on the results of the government’s post-Grenfell cladding tests, in which flames reached the top of a model wall with Grenfell-style cladding in less than seven minutes.

While he considered the panels to be the primary cause, he added that the use of combustible insulation in the cladding system, the presence of “extensive cavities” in the cladding system and the use of combustible insulation in window frames “may also have contributed to the fire’s spread”.

In the refurbishment of Grenfell Tower, vertical aluminium cladding rails were added to the outside of the building, resembling columns that extended from the face of the tower.

Cavity barriers, according to the report, were cut to make room for the rails, “and no cavity barriers were placed within these rails”, meaning fire could have spread up the cavities inside without being blocked.

Flames spread down, as well as up, the face of the tower, partly due to falling debris and molten polyethylene from the core of the cladding panels flowing downwards over the walls, the report said.

This video was compiled by Professor Luke Bisby to create a chronological representation of how the fire spread. It contains footage of Grenfell Tower on fire and may be distressing for some viewers.

Professor Bisby added that the “architectural crown detail” added to the top of the tower during the refurbishment “played an important role in increasing the rate and/or extent of lateral fire spread”.

This crown, at the top of the vertical rails, was – like the cladding panels – mostly made from ACM with a polyethylene core. Some of the edges were exposed, meaning flames could easily get to the combustible core, the report found.

Professor Bisby found that there was insufficient evidence as yet to determine the cause of the fire, or to say with certainty that it was a Hotpoint fridge-freezer in a kitchen.

This was also the conclusion of another report to the inquiry by Professor Niamh Nic Daeid, who looked into the cause and spread of the fire in the original flat and how it got out of that flat.

Update: at 16.23 on 4.6.18 This story was updated to include a video created by Professor Luke Bisby.