West Sussex Highways is set to fix a bridge along the A283 on the outskirts of Upper Beeding.
Court Bridge, which crossed the River Adur north of the old cement works, is leaking water and needs to be repaired to prevent it deteriorating.
Engineers uncovered the issue after a routine inspection.
Parts of the bridge will be replaced and the road on top will be resurfaced.
Work starts on Monday, June 19 for five days between 6.30am and 7pm.
It will then continue over two consecutive weekends, from 8pm on Friday, June 23 to 6am on Monday, June 26 and 8pm on Friday, June 30 to 6am on Monday, July 3.
During the first week, traffic will be controlled by temporary traffic lights, manually controlled at peak times.
Over both weekends the bridge will be closed.
A fully signed diversion route will be set up via the A27 and A24 for road users to follow.
West Sussex County Council’s Cabinet Member for Infrastructure and Highways, Bob Lanzer, said: “This is important maintenance work we carry out regularly on our bridges to keep them safe for road users.
“Work of this nature does require a road closure over the weekend, so we ask motorists to follow the signed diversion routes.
“There is likely to be disruption, so please allow extra time for your journeys if you are travelling this route.”
The scheme costs £120,000.