Corby councillors are being asked to approve a further £600,000 spending on the Cube to make the building watertight.
The request, if approved, will bring the bill for the civic building, which was expected to cost £36m, up to £48.2m so far.
The additional cash is needed to carry out work on the flat roof on the building’s fourth floor which has consistently leaked into the council chamber, the councillors’ room and other areas.
Leader of Corby Council, Cllr Tom Beattie, said: “We have made a lot of progress in bringing the Cube up to the standards we expect.
“There is still an outstanding issue involving leaking in parts of the roof and a temporary wall which we are actively pursuing the building’s original designers and contractors to resolve.
“In the meantime, in order to prevent further delays in securing a suitable tenant for the fourth floor we are independently taking measures to make the roof watertight.”
According to a report to be discussed by the council’s One Corby Policy Committee meeting on Tuesday, September 3, the fourth floor roof needs substantial repairs, including the removal of the remaining trees and soil from the rooftop garden.
The report says there has been little interest from businesses in using the fourth floor as a restaurant, as originally planned, but discussions are now taking place with a potential business user who may pay for the area to be fitted out as offices in return for a rent-free period.
Corby Council is in negotiations with the Cube’s design team, led by Hawkins Brown, and the main contractors Galliford Try over the leaks and other issues.
Hawkins Brown says the leaking roof is not a design problem but Galliford Try disagrees and insists the issue has nothing to do with workmanship.
Chief Executive of the borough council Norman Stronach said: “I do not want to have to ask for more money but if we don’t take action now the problem will get worse.
“There will be difficult discussions ahead with the design team and the contractors, in the meantime the building needs to be made watertight.”
The council hopes to recover the cost of the roof repairs from the design team and the contractor.