The cladding firm tasked with the Grenfell Tower refurbishments failed to check fire-resisting measures with the architects, the inquiry into the blaze has heard.
Fire-resisting cavity barriers were not installed around the windows on the building, after the designer who translated architects’ drawings into a construction-ready form failed to double-check ambiguous aspects of the architects’ concepts.
Kevin Lamb, a freelancer hired by cladding specialists Harley Facades, said he followed the drawings of architects Studio E, sent his drawings back to them, which were approved, and that the “buck stopped” with them.
During proceedings on Thursday, drawings for windows from Studio E provided to Mr Lamb around March 2015 were shown.
Inquiry lawyer Kate Grange QC said an inquiry expert analysed them and “was not clear whether a cavity barrier was marked there”, and asked whether Mr Lamb considered double-checking with Studio E whether they were supposed to be there, in line with building regulations and guidance.
Mr Lamb said it was discussed internally at Harley, but it was decided if the architects wanted it, it would have been made clearer and shown on the sill level of the drawings.
Inquiry chairman Sir Martin Moore-Bick said: “You were translating the architects’ drawings into fabrication drawings, so you needed to understand yourself what was shown on the architects’ drawings didn’t you?
“It sounds as though there was some debate within Harley as to what these drawings did actually show, and you didn’t think it appropriate to say ‘well I really need to hear from the architects so I can do the right sort of drawing’.”
Mr Lamb said: “Correct, correct, but obviously everything Harley told me to do would supersede that… I was happy with advice from Harley.
“They were the cladding specialists, they obviously felt it wasn’t necessary, or they’ve had discussions, I don’t know.”
Mr Lamb agreed with Ms Grange that there was a requirement for cavity barriers around windows under building regulations, and they were “not an insignificant detail” and were “potentially relevant to life safety”.
Ms Grange said: “For a detail that’s that important in terms of life safety, external and internal fire spread… why wouldn’t you want that expressly flagged and considered carefully by all of the design team?”
Mr Lamb said: “My superior, my client, gave me confidence to do exactly what I did, which was to follow the architect’s drawings.
“By virtue of following his drawings, we’ve produced our drawings and he’s approved them. You can expect that he’s happy that there is conformance.”
He disagreed it was “obvious these were very early drawings” and that it was his job to develop the design, “including developing the design of the cavity barriers”.
Mr Lamb, who has 30 years experience in design and manufacture within the cladding industry, said: “I think they are quite detailed as far as an architect’s drawings are concerned.”
In his evidence on Wednesday, Mr Lamb had said: “The architects reviewed Harley’s drawings and as part of that process I would expect any non-compliance with the building regulations and in particular parts related to fire safety to be picked up and flagged.
“I assumed that Studio E had the benefit of specialist advice from, amongst others, fire specialists.”
During the inquiry’s first phase, expert Dr Barbara Lane found that “the construction detailing around the windows, including the materials and their arrangement, increased the risk of a fire within the flat breaking out into the large cavities surrounding the windows”.
The inquiry’s phase one report added: “She also emphasised that the windows were not provided with any fire-resisting cavity barriers and instead were surrounded by combustible materials… in her view, if a fire started near a window, there was a disproportionately high probability that it would spread into the cladding regardless of how it had started.”