A combination of the 150mm thick flammable insulation and bad design of the area around the windows were the main problems. The exterior work was all about the insulation and using it to meet environmental("Green") rules. The cladding was only around 3/4mm thick and there to protect the insulation. I doubt even a 2mm layer of Napalm could produce that ferocity of fire on the outside of the building.
The manufacturers of the insulation listed it as the
only one of its type to be rated for use above 18m. Any architects/designers would also have had to look at the small print connected to its usage. Which was basically surrounding it with non-combustible materials in order to restrict spread of fire to adjoining flats. But they would simply see in a list of potential materials(eg on the RIBA/Royal Institute of British Architects website) that it was ok for use above 18m and that was it. The 18m limit was only because of the height limit of fire brigade ladder reach and no other aspect. Plenty of buildings around the world have used it. It is strange that the original specification of the insulation was for similar product from the same manufacturer, but wasn't rated for use above 18m.
The new design of area around the windows meant there was little to prevent the spread of any fire from inside a flat to the outside and then back into another flat. The initial internal fire had been put out successfully, which is why the building wasn't immediately evacuated.
Quote:
Then there was a Non-Material Amendment made to approval PP/12/04097 after CON/14/04024. On 2 January 2015 proposed changes to the design by Studio E and planning consultants IBI Group were accepted by RBKC planners as NMA/14/08597. The design changes appear very material in that they re-position the windows, out from the existing concrete into the (rainscreen) cladding zone.
Ian notes that the planned separation of the window from the concrete meant that interfaces – “window, head and cill extrusions, foams, perimeter filler insulation, water, air and vapour barrier, and lining boards” – became technically critical for fire safety.
The several materials and products within the interface gap became the only construction stopping a fire inside a flat from reaching the cavity and cladding.
In other words, the late change to the window position, moving it out from the solid concrete structure, meant it was weak due to the ‘filled gaps’ around the sides where fire could break through
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Non-experts have to rely on the expertise of the experts, ie Architects and designers. Who in turn have to rely on other experts and the manufacturers.