A leaked report about the Grenfell Tower fire disaster, in which 71 people died, has identified deficiencies in the installation of the windows, cavity barriers and cladding system.

The BRE Global report, which was leaked exclusively to the London Evening Standard, said that the refurbishment fell short of building regulations, and that the 2014-16 refurbishment failed, in several fundamental areas, to meet fire safety standards set out in the building regulations.

The BRE report said that Grenfell Tower, as originally built, appears to have been designed to provide very high levels of passive fire protection.

The cavity barriers installed during the refurbishment were of “insufficient size specification” to perform this vital function. Some cavity barriers were installed “upside down” or “back to front”, further retarding their effectiveness.

The result was to create a chimney-like effect in the gap between the cladding and the concrete surface that “provided a route for fire spread”.

The window frames were “significantly narrower than the gap between the concrete surfaces of the columns, 150mm narrower”, leaving large gaps at either end. These spaces were filled by a rubberised membrane, rigid foam insulation and uPVC lightweight plastic panels — but crucially “none of the materials used would be capable of providing 30 minutes fire resistance”.

BRE notes that the 75mm insulation foam used on most of the spandrel beams had “no markings to identify the manufacturer of the foam”.

The aluminium composite material used in the facade had a polyethylene (plastic) core that “appears to be highly combustible” and “appears to have provided a medium for fire spread up and across the facade”.

The “absence of door closers” on many front doors to flats, contrary to building regulations, resulted in a significant number of doors being inadvertently left open when residents fled.

“Where this occurred, the fire in each flat appears to have emitted large quantities of smoke and later fire directly into the immediate lobby, and these have gone on to affect the lifts and single stairwell”.

This may have created “shortcomings in compartmentation” of the fire and would have affected residents’ life chances as they sought to escape down the single stairwell.

BRE notes that individual breaches relating to the cladding system assume far greater importance when “considered in combination as opposed to when they occur in isolation”.

The draft report, according to the Standard, was submitted to the Metropolitan Police Service so that its interim conclusions could speed up “other parts of the MPS-led investigation”, including gathering documentation and interviewing contractors.

London Evening Standard