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
Philippa has the weekend weather for the east
Philippa has the weekend weather for the west
Landmarks across the south will switch off their lights for an hour tonight as part of action on climate change.