Glass above a door to a flat in a high rise tower block in the City failed fire tests in less than five minutes.
The sample door set, which included a fanlight glazed section above the door at Great Arthur House near the Barbican, failed tests within a matter of minutes.
A door set of its age and type is expected to provide 15 to 20 minutes fire resistance, but the glazed fanlight fell far short of that in tests in March.
Current guidance is that doors should withstand fire for 30 minutes – but most authorities opt for an hour. The City Corporation is replacing doors with sets which can withstand fire for 60 minutes.
An undamaged door taken from Grenfell Tower lasted 15 minutes in tests, but the tragedy was caused by combustible cladding.
After results came back the Square Mile authority upgraded the doors.
They had been designed and installed to comply with the building regulations of the time.
The 1950s block is grade II-listed and needs listed building consent for any work. It was one of London’s tallest residential towers when it was built.
Paul Murtagh, Assistant Director of the Barbican and Property Services, said: “The door sets failed because of the fan light space above.
“We did some intermediary work to upgrade those fan light doors to make sure they improved the integrity of the doors and frames.”
And he explained that some leaseholders in the 16-storey block had not allowed work to be done.
The Corporation is also replacing all the doors on its estates, which should take 18 months and is just going out to tender for sprinklers.
In 2013 the City of London commissioned work to replace windows at Great Arthur House.
After the disaster at Grenfell the Corporation extended the work to look at and remove the cladding insulation on the outside of the building.
The project won the RIBA National Award and RIBA London Award last year.
In October 2017, following the Grenfell Tower Fire, a fire risk assessment for the block noted: “The flat entrance doors are consistent throughout the block.
“They do not comply with current standards. They appear to be of substantial construction, are not provided with a self-closing device, sufficient fire rated hinges, strips or seals, or substantial rebates.”
Ward Councillor Sue Pearson, said: “The testing of door sets is horrendous. It says they failed in less than five minutes.”
Councillor Pearson who is a former architect added: “It’s concerning to me.”
A Corporation spokesperson said: “The safety of our tenants and leaseholders is paramount.
“In the last year we have worked hard to enhance the security of residents living in our housing portfolio in the event of a fire.
“Following a Fire Risk Assessment at Great Arthur House we immediately installed a ‘Waking Watch’ for 16 weeks whilst we undertook a series of actions including improvements to the fanlight section of the door frame and installing a full hard-wired fire alarm system.
“All residents in Great Arthur House were also given a smoke detector.
“We are replacing all front entrance doors in every block of flats across our housing portfolio – including Great Arthur House – to provide 60 minutes fire resistance wherever possible.”
Councillor Pearson asked whether the stay put policy for the block was still in place.
Mr Murtagh said there is a full fire alarm system in the block and the Corporation also wrote to all the residents.
If there were an emergency, residents two floors above and one floor below would have to be evacuated, he explained. They also put up signs in the block.
“The immediate situation was dealt with. We reacted immediately and did something,” he said.
The Corporation worked with fire safety experts and the London Fire Brigade.
The measures include: fitting a permanent hard-wired fire alarm system; individual smoke detectors to all flats; upgrading of all fire safety signage to reflect the new evacuation arrangement; and new evacuation process for residents in the event of a fire.