The Highways Agency said it decided to keep the Boston Manor Viaduct closed because during works it found a crack in a "sensitive location", which requires it to be kept closed until it is repaired.
Diversion on the A312 and the A4. Drivers are being advised to allow extra time for their journeys.
More top news
Sunday's weather update for the east with Philippa
Sunday's weather update for the west with Philippa
Philippa has Sunday's weather for the east