Grenfell Tower report: How the fire began on the fourth floor and spread throughout the block in minutes
One of the most extraordinary aspects of the BRE report into the Grenfell Tower disaster is that it hammers home how a fire in a single fridge-freezer can go on to consume a 24-storey building if adequate fire safety mechanisms have not been put in place to stop it.
This is an abridged version of BREâs suggested narrative of how the inferno started and the route it took as it spread:
1 The fire began on the fourth floor
It started in Flat 16 in a fridge-freezer situated within one metre of the kitchen window. This window was in the tilt-open position. Constructi on of the window breached building regulations and failed to provide âany substantial barrierâ to the fire taking hold in the facade outside.
2 The facade ignited
Once the flames breached the window, BRE suggests several options as to what happened next: that the flames ignited the âhighly combustibleâ polyethylene core of the aluminium cladding; that they ignited the âcombustibleâ foam insulation; or that they took hold of the âflammableâ materials around the window frame. Or several of these things could have happened at once.
3 Flames fanned up, across and down the facade
BRE believes the fire spread up the column adjacent to the kitchen of Flat 16, assiste d by âcombustible components in the construction and lack of appropriate subdivision of this fuel to prevent one component involving the nextâ. Flames also spread laterally, aided by the same shortcomings. The impact of flames entering the cavity between the concrete and the facade was exacerbated by the lack of adequate cavity barriers. These failed to seal the gap and created what appears to be a calamitous chimney-like effect. Downward fire spread also occurred, âas a result of burning droplets of polyethylene falling and igniting combustible materials belowâ.
4 Fire entered the other flats
As flames fanned out across the facade they encountered windows of other flats. BRE believes the same deficient construction around the window that l et the fire escape from Flat 16 now afforded it a route to spread back into the other apartments.
5 Fire burned within the flats
Once the blaze was in any one apartment, it would burn from room to room at a speed that depended on whether or not doors inside were closed. Any single flat, once caught up, âwould be substantively destroyed, as a flat is normally designed to be a single fire compartmentâ.
6 Fire and smoke entered the lobbies and stairwell
As residents fled, the lack of door closers meant some front doors did not automatically close, allowing flames and smoke to billow out of flats into the central core, including the lobby and stairwell, impinging on the means of escape for residents further up the tower.
BRE do not provide a specific timeframe for this suggested sequencing.
Waste chute rooms could have saved lives
The report says: âIt is worthy of note that every one of the waste chute rooms has survived intact, having been protected by the fire-resisting doorâ.
These rooms were accessed from the lobby on each floor and situated near the stairwell. It raises the poignant possibility that if trapped residents had sought shelter in the waste chute room on their floor, they might have been saved.
The report shows photographs from the 13th floor which contrast the fire-damaged lobby and exterior of the waste chute room door with the barely blemished interior of the waste chute room itself.
It says: âBin chute rooms have been largely undamaged. Whilst the fire has been kept out of these rooms, it is unclear whether the atmosphere within these rooms would have sustained life [during the fire].â
Sprinkler system might not have made a difference
The fact that the tower had no sprinkler system means that, like many buildings erected in the Seventies, it did not conform to current building regulations which require that blocks of flats over 30 metres tall have sprinklers inside each flat. But w hat was the impact?
BRE says once the fire had taken hold across the facade and ignited more than four flats, a sprinkler system was âvery unlikelyâ to have made âany appreciable differenceâ.
Sprinklers could only have altered the outcome if they had âprevented the fire from leaving Flat 16 and igniting the claddingâ.
Yet if a sprinkler had been installed in the middle of the kitchen ceiling, they said, âit is possible the chassis of the fridge freezer might have shielded the fire from the sprinklerâ. This will be tested by reconstructing the fire in Flat 16 off-site and testing a sprinkler system.
How close was the Tower to collapse?
BRE says that the fire burned âat a level of severity which would significantly impact upon the fire resistance of the structure for between nine and 12 hoursâ.
The original tower block, built with reinforced concrete in 1972, had floor slabs 10 inches thick and walls 12 inches thick, which tapered to eight inches from above the 13th floor.
Standard fire resistance tests show that eight-inch walls provide only six hours of fire resistance.
However, the thicker lower walls and floors exceeded the girth for which tests have been conducted. This appears to have saved the building from collapse. BRE conducted independent tests to assess âspallingâ (break-up and buckling) of the concrete and exposure of the buildingâs reinforced steelwork to determine how close to collapse it was.
It concluded: âThe physical evidence confirms parts of the structure very close to their point of failure.â Had the building been built to the lower requirements of current building regulations, âit is likely the tower would have collapsedâ.Source: Google News