The £4.4m Heartsease roundabout revamp has fallen a month behind schedule because of "unexpected" problems with drainage.
And the delays mean a planned full closure of the roundabout - likely to cause Norwich drivers major headaches - will now not coincide with the Easter holidays, as had been planned.
Norfolk County Council bosses had hoped the final phase of the scheme, to shut the roundabout completely for four weeks to allow resurfacing, would start on March 26.
County Hall officers had planned that to coincide with the school Easter holidays, a time when there would be less rush hour traffic on the city's roads.
But the council said the scheme is now four weeks behind schedule, mainly due to "an unexpected issue with drainage", along with a number of "smaller issues" which needed to be resolved.
READ MORE: Heartsease businesses facing drop in footfall and trade
People and businesses in the area will receive letters today informing them of the change in timings for the full closure.
The closure is now due to happen on Saturday, April 13, with the council applying for a five-week permit, ending on Saturday, May 18.
The council says it hopes the resurfacing work can be done in a shorter time frame than five weeks, but has factored in extra time in case of delays, such as poor weather.
Graham Plant, cabinet member for highways, infrastructure and transport, said: "I know that the planned closure and extension to work at Heartsease will add to the frustration people are feeling, so I'd like to thank everyone affected by the work again for their patience as we look to the final phase.
"We will do everything we can to minimise disruption and complete the work as quickly as possible when the time comes.
"It’s a large-scale project in a very busy area of the city’s network, but one that's vital to complete – not only to provide much-needed facilities for those walking, wheeling and cycling but, at the same time, to improve the roundabout’s currently very poor safety record.
"We’ve had strong public demand to improve this junction for several years and we can now look forward to work finishing on site and enjoying the benefits of a much safer and more pleasant experience for everyone who uses or travels through the area."
Harvey Lane, Plumstead Road East and Margestson Avenue have been fully closed during the work.
Three arms - Heartsease Lane, Plumstead Road and St Williams Way - have, so far, stayed open.
But they will also have to close during the resurfacing work.
WHAT WORK IS BEING DONE AND WHY?
The revamp of Heartsease roundabout - one of the busiest in the city - started in September last year.
Paid for using a slice of £32m Norfolk County Council was awarded by the government, the council said the changes will improve safety.
The work is changing the alignment of the roundabout, so there is just one lane around it, which the council says will slow traffic down.
The changes include one-lane entry and exit, along with new pedestrian and cycle crossings.
Pavements will be converted to shared-use pedestrian and cycle paths and widened to segregated pedestrian/cycle paths where possible.
The council says the resurfacing work will involve building up of the road by up to 40cm in some places.
It says the work needs to be completed in layers to minimise surface joints, with cooling time of up to a day between each layer so materials set properly before the next is added.
The council also needs to reverse temporary work done at the Aldi entrance which allowed access during the project construction.
The project has been controversial. Businesses said it has badly hit their trade, while Norwich Cycling Campaign said the scheme was a missed opportunity.
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