St Alkmund's Place and Church Street in Shrewsbury will not reopen until November 6.
Traffic marshals will be used to oversee access for deliveries via Fish Street between 7am and 6pm every day.
'Access to Businesses Only' and 'No Through Road' signs will be set up on Fish Street from 6pm to 7pm each day.
Traffic will be able to use Pride Hill to reach the town's main one-way system.
Meanwhile, pay-and-display parking on Victoria Avenue, which runs next to the River Severn between the Quarry and Welsh Bridge, will be suspended from October 19 for almost three weeks.
Charges will be suspended for 19 days while a trench is dug and work carried out on low-voltage underground cables.