NZ Transport Agency contract manager Mark Stewart
described the work on the bridge, which is more than 100 years old, as "urgent".
Work on the State Highway 8A bridge involved the installation of scaffolding, the replacement of running boards, the installation of sub-beams and abseiling work to check and tighten all deck bolts.
The decision to close was taken as activity would be both above and below the single-lane bridge.
During the closures an alternative route will be available via Camphill Rd, Kane Rd, SH8A and SH6.