The Kings Highway at Clyde Mountain will be closed in both directions at night between 6pm and 6am, Monday to Thursday for about three weeks from October 12, weather permitting.
A Transport for NSW spokesperson said maintenance work will be carried out including slope stabilisation in response to recent rainfall.
"Detours for light vehicles will be via the Princes Highway and Nerriga Road and are expected to add up to 3.5 hours to journeys," the spokesperson said.
"Detours for heavy vehicles will be via Picton Road, and the Princes, Hume and Snowy Mountains highways and are expected to add up to 3.5 hours to journeys.
"Work will also be carried out in the day between 6am and 6pm, Monday to Thursday and 6am and 12pm (midday) on Fridays."
During day time work hours, traffic control, lane closures and a reduced speed limit of 40 kmh will be in place. Delays of up to 10 minutes can be expected.
The road will be open from 12pm (midday) on Fridays until 6am on Mondays to allow for weekend traffic.
Motorists are advised to drive to the conditions and follow the directions of signs and traffic control.
Transport for NSW thanked the community for its patience while work is carried out.
For the latest traffic updates call 132 701, visit livetraffic.com or download the Live Traffic NSW App.
READ MORE: Wharf Road slip way opens October 9