Plans for the urgent fire safety works are to be discussed at the Guildhall on Monday by the Square Mile authority's housing management and almshouses sub-committee.
The City of London Corporation has 33 housing blocks of six storeys or more. Nine of these are in Southwark, including the Avondale Square Estate on the Old Kent Road which has three 19-storey towers.
After the Grenfell Tower disaster in Kensington the corporation ordered a check of all its blocks for the use of cladding materials.
"Our returns confirmed that only Great Arthur House [at Golden Lane] and Twelve Acres House (the new block at Avondale Square Estate) include cladding," said Andrew Carter, director of community and children's services, in his report to the sub-committee.
"The cladding at Twelve Acres House is a small area of rainscreen, which poses no risk."
The City now plans to embark on a major scheme to upgrade the front doors of the flats in all its blocks.
"The majority of entrance doors to individual flats in our blocks are original and, in general, give fire resistance of 15-20 minutes. There is no legal requirement to replace these with more fire resistant doors.
"We have replaced doors with more fire-resistant models as they required repair or were due for replacement, and had intended to continue with this programme.
"However, we will now be embarking on an enhanced front door replacement programme to bring all front doors up to a 60 minute fire resistance standard, starting with our tower blocks.
"The cost of this is estimated at £3 million-£5 million, depending on the level of specification and coverage required.
"Consideration will need to be given to a number of factors, including planning guidelines (for buildings with listed status or in conservation areas) and possible objections from leaseholders to having this work imposed upon them."
The City has already commissioned a feasibility study to evaluate the potential for retrofitting sprinkler systems and fire alarms into its tower blocks – estimated at a cost of £15 million to £20 million.
The report warns that the costs of these works is likely to affect the City's ambitious plans to build 700 new homes on its estates, including many new homes in Southwark.
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