The closure of the QEII Bridge is due to be in place from 10pm on Saturday until 5.30am on Sunday, although the exact timing of the closure will be subject to traffic levels.
The gantry being installed at junction 1a of the M25 will house information signs for drivers.
The southbound M25 will be closed from junction 30 to junction 1a, with a clearly signed diversion in place via the A13, Blackwall Tunnel and A2 to the M25 junction 2.
Following the planned closure, between 5.30am and 8am, only 1 lane will be open over the QEII bridge; this is so that structural surveys can be safely carried out on a footbridge between junction 1a and 1b.
The M25 clockwise junction 31 entry slip road will also be closed at the same time, with a diversion in place to junction 30 instead.
Members of the public should contact the Highways England customer contact centre on 0300 123 5000.
Journalists should contact the Highways England press office on 0844 693 1448 and use the menu to speak to the most appropriate press officer.