The A291 Sturry Hill between Canterbury and Herne Bay will remain closed until well into next week.
Southern Water is carrying out emergency repairs to a drain following heavy rain earlier in the week.
There had been hopes that the road would reopen today, but the firm now says the road will remain closed until Wednesday at the earliest.
Bus firm Stagecoach is rerouting services.
The closure means Stagecoach buses will not be using stops between Vauxhall Avenue in Canterbury and Sweechgate at Broad Oak.
School services and the Triangle 6 and 7 will instead travel from Canterbury to Herne Bay via Vauxhall Road, Broad Oak Road and then on to the A291 where it meets Sweechgate.
Herne Bay to Canterbury is via Popes Lane, Babs Oak Hill and the A28 Island Road.