Construction work at Preston's bus station car park will impact on families coming to the city for graduation week, council bosses have said.
Lancashire County Council had hoped to have two levels of the busy city centre facility re-opened in time for the week beginning July 10.
However, a week's delay means fewer spaces will be available during the University of Central Lancashire's graduation period.
County Hall has said the overall redevelopment plan has not been delayed and steps are being taken to minimise any disruption.
But visitors have been advised to make alternative arrangements in the event the car park reaches capacity.
Andrew Barrow, Lancashire County Council's project manager for the bus station redevelopment said: "Levels four and five should reopen by Monday, July 17, with work then moving to parts of levels one and two.
"We had hoped that this could be ready ahead of schedule for UCLan's graduation week, but this has not been possible due to an unscheduled issue, which is now being resolved.
"This means that there will be fewer spaces than usual during next week. People may need to make alternative arrangements during the graduation week, as this is usually a very busy time.
"The lift in the central stairwell is currently being replaced as part of the redevelopment. The other two stairwells and lifts are still in use.
"We're doing everything we can to minimise the disruption during this work, which can affect the areas that are open at any specific time. We apologise for any disruption and ask people to bear with us."
The Grade II listed building is undergoing a major overhaul worth £23m.
Mr Barrow added: "The redevelopment of the car park is on schedule and has already resulted in improvements to the higher levels."
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