A detailed inspection by engineers working on Cleveland Bridge in Bath has revealed worse than previously identified damage to the concrete trusses supporting the deck.
Repair work is progressing on the Grade II* listed structure, which usually carries 17,000 vehicles a day.
Prior to the current closure, preparation work had already got underway to erect scaffolding around the bridge.
Council leader Councillor Kevin Guy and cabinet member for Transport, Councillor Manda Rigby met staff from contractor Dyer and Butler, who are carrying out the repairs on behalf of Bath & North East Somerset Council.
Cllr Guy said: “It is a significant engineering project and being able to meet the team working on site and to look under the bridge deck at the trusses was a real eye-opener.
“Since our visit, however contractors carried out further detailed inspections which have shown the extent of the damage which is worse than identified when engineers, using ropes to access the trusses, carried out a survey last year.”
Councillor Manda Rigby, cabinet member for Transport added: “Our project team are working with the contractor to maintain our original programme, but there remains a risk that once the damaged concrete is removed, defective reinforcing bars are found.
“We do appreciate the closure causes disruption and we want to thank people for their patience. As the recent detailed survey has shown, the nature of the work meant we didn’t have any alternative but to close it.”
Work is continuing to the west side of the deck, removing the existing bedding and waterproofing.
Though the bridge has been closed to motorists, access remains for pedestrians, cyclists and the emergency services.
The £3.8 million project, funded through the Government’s Highways Challenge Fund, began in May with traffic filtered over the river crossing by temporary traffic lights as scaffolding was erected.