Last month the Evening Times revealed two weeks of works were to hit Nelson Mandela Place as contractors replaced water mains. Now roads chiefs have announced an extra time will be required.
Subsidence has been blamed for the extension which will see Nelson Mandela Place and West George Street, between West Nile Street and George Square, remain closed until Friday.
Roads chiefs say West George Street will operate as a two-way road from Buchanan Street to George Square to allow access, but motorists are being warned to experience delays, especially at peak times.
A Scottish Water spokesman said: "We apologise for any inconvenience to road-users, but it has been necessary to extend the temporary closure because of some subsidence on the road near Queen Street Station.Nelson Mandela Place was closed from January 21 to enable Scottish Water's contractors to progress with work on the upgrading of water mains in the city centre.
"We had anticipated re-opening the road by today but, due to the subsidence, we have had to extend the road closure until February 8 to allow us to investigate the cause of the subsidence and carry out any repair work."
Local diversions will remain in place to allow road access to George Square.
Scottish Water say the £3.5million water mains upgrade, which started in July 2012, will reduce the risk of bursts and the inconvenience to customers, road users and pedestrians.